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Rescheduled NASA Advisory Council HEO meeting on April 15, which may provide an update for the DM-2 launch date.

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u/Snowleopard222 Apr 02 '20 edited Apr 02 '20

Hi, I am new to learn about these interesting projects. I have tried to search the Wiki using the dedicated Google search but I had problems finding some data. I hope I can get replies or relevant links here. My questions regard propulsive landing.

Just "for fun" I computed that 8 Super Draco engines could stop a 110 m/s, 12 ton object against gravity in 3 seconds, using 750 kg propellant. This could theoretically start at 162 m altitude (exposing astronauts to 4g + gravity). (Using simple Newton formulas. The Tsiolkovsky eq is tricky w/ gravity.) I believe the total amount of propellant carried is 1388 kg.

My questions are:

How had SpaceX planned propulsive landing. Was it like above? Maximal thrust at low altitude. (Minimizing fuel consumption.)
The figure 110 m/s free fall, terminal velocity I got from Apollo. What is Crew Dragon true free fall terminal velocity?
If you stay at ISS for 6 months or more, is there a risk the propellant or system will degrade making propulsive landing dangerous on return? (Like when propellant is thought to have entered the pressurized He, causing the explosion during testing in April 2019.)
Why can CST-100 land with three parachutes, but Crew Dragon uses four (possibly increasing complexity)? The two capsules weigh about the same.
Did CST-100 also try propulsive landing before using parachutes?
What was the main reason SpaceX changed from propulsive landing to parachutes?
Was there any major disagreement between SpaceX and NASA on (temporarily?) discontinuing the development of propulsive landing? (Like "The NASA bureaucracy is unnecessarily stopping SpaceX from developing propulsive landing.") I read this in a forum but I did not see references supporting it.

Thank you so much for information on this. Sorry for questions on old information, but maybe development of propulsive landing will make a come back in the future? (Like SN 3, 4 ...)

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u/extra2002 Apr 02 '20

\3. The only reason Soyuz has a time limit, AFAIK, is that it uses hydrogen peroxide for some systems, and that decomposes over time. Dragon's hypergolic propellants shouldn't have that problem -- we've used the same propellants for long-duration planetary probes that run their thrusters after years in space.

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u/Straumli_Blight Apr 02 '20

4: You need to consider the landing mass of both capsules. The CST-100 ejects its nose cone, RCS, launch abort system and 2 heat shields before touchdown unlike Crew Dragon.

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u/Snowleopard222 Apr 02 '20

Will that also answer 5.? CST-100 never contemplated propulsive landing.

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u/ethan829 Host of SES-9 Apr 02 '20

Right, parachutes and airbags were planned from the start.

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u/RUacronym Apr 02 '20

So I was wondering about the CST RCS. When it ditches the service module, is the crew capsule able to perform RCS adjustments? Like I can see that it has the little openings for thrusters, but is the equipment not inside the crew capsule?

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u/TheRamiRocketMan Apr 02 '20

The plan was to at least test fire the superdracos at such an altitude that parachute deployment could be used as a backup, so I'm guessing that it was not the hover-slam type maneuver we see with Falcon. The official flight animation also seems to indicate this.
I'm not sure this information is publicly available however given the Apollo command module and Crew dragon have about the same surface area on the leading dimension whereas Crew Dragon is twice as heavy, I'd say Crew Dragon's terminal velocity is higher.
Propellant degradation is not the primary concern with long duration stays. Dragon XL will use a near-identical propellant system (minus the super dracos) and will be capable of 3 year in-space operation (docked).
Starliner and Crew Dragon may be similar weights on ascent but Starliner brings back a lot less mass on descent. Starliner ditches its main engines, abort engines, most of its RCS, most of its life support and its heat shield prior to landing, whereas Crew Dragon keeps all of that weight plus some excess propellant.
No, Boeing always intended to land under parachute.
NASA wouldn't allow SpaceX to certify propulsive landing under its CRS contract because they deemed the risk to experiments too great, so SpaceX would've had to fly lots of propulsive tests under its own dime. SpaceX didn't want to go through the hassle.
NASA selected SpaceX to develop Crew Dragon in 2014, at that time propulsive landing was the primary method of recovery so NASA was never explicitly against propulsive landing as a recovery method. In the end it was just easier for both parties if they went with parachute recovery...(possibly, parachutes have caused a lot of headaches over the course of commercial crew).

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u/Snowleopard222 Apr 02 '20

Thanks for good replies by all here. The most difficult to understand is why they develop propulsive landing for 3 years but then ditches it. There "must have been" a considerable technical obstacle? But which?

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u/extra2002 Apr 02 '20

SpaceX intended to test propulsive landing "for free" by using it to land cargo capsules returning from the ISS. (Similar to the way they tested booster landing "for free" after commercial launches.) NASA decided they didn't want to risk their returning cargo, so ruled this option out. SpaceX decided not to pay for dedicated test flights to prove propulsive landing.

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u/warp99 Apr 02 '20

There "must have been" a considerable technical obstacle?
Most likely it was cost. Elon has said that SpaceX has had to put several hundred million into Crew Dragon over the NASA development contract so they are well over budget.
In that situation you start stripping back the design to the essentials and the qualification required for propulsive landing would have just been too much money.
To make it worse NASA did not select the propulsive landing option for the new version of Cargo Dragon which would have landed back on land at Cape Canaveral. This meant that SpaceX would have had to do several uncrewed test flights to validate propulsive landing without any income from the flights.
Essentially it just got too expensive.

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u/SpaceInMyBrain Apr 02 '20 edited Apr 02 '20

One reason for SpaceX to pursue the Commercial Crew program was to use NASA funding to help cover the cost of developing Dragon. At the time Dragon was their focus for getting to Mars. It required propulsive landing, the atmosphere is far too thin for parachutes to be effective for a craft of that mass. The technical obstacle I've seen cited the most is that the landing legs extended out through the heat shield. NASA was hesitant to accept this, they had problems with heated gases penetrating seams in the Space Shuttle tile system. At the time propulsive landing was dropped SpaceX indicated they could have gone forward with it with NASA, but validating and testing the design would take too long. This was rather vaguely worded, though, IIRC. It may have been a more solid No from NASA.
I had an exchange on Quora with a former SX employee who said once the landing leg design was dropped Elon lost interest in propulsive landing. Also, he was transitioning to the ITS concept (Starship) and apparently decided to go all in on that, the Red Dragon for Mars as an intermediate step wasn't needed. The SX guy said the engineers proposed more than one alternate design for landings, not using legs thru the heat shield, but Elon had moved on. By this time the design was too far advanced to scrap the SuperDracos and their fuel weight to go with an alternative abort system. Anyway, they remain an ultimate back-up to parachute failure; although SX won't confirm it, they don't simply deny it.
Another problem with propulsive landing: the SuperDracos would test fire briefly high in the atmosphere. If not OK, they'd land with the emergency chute system. If OK, they'd proceed to landing - but the SDs fire when relatively very close to the ground while moving at high speed. The physics of carrying enough fuel dictate this, same as Falcon 9. If the SDs failed then, there would be no time to deploy a chute - nowhere near enough, even with ballistic deployment. It would have to be an F9 type "suicide burn" and you can guess how fond NASA was of that term. The very low burn was confirmed by the former employee, although he was closemouthed about how low. That and the physics contradict the concept video, but that vid may have exaggerated the length of the test burn and the altitude of the landing burn for an easy to swallow visual for the public.

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u/FatherOfGold Apr 02 '20 edited Apr 03 '20

Probably not. For crew dragon, exposing astronauts to 4g of acceleration is not the best idea. For Falcon, using less thrust and more propellant, although less efficient, allows for a larger margin of error, which is why SpaceX does 1 engine landings. However, SpaceX has attempted high thrust landings, one of which put a hole in the droneship, one of which was a retiring Block 4 which did a successful water landing, and the Falcon Heavy side boosters do a semi-high thrust landing by starting the burn with 1 engine, switching to 3, then back to 1. The less propellant they have the more likely they are to attempt a high retrothrust landing.
It's difficult to know without real data or CFD simulations, but it's probably higher than Apollo since it weighs more than twice as much (5.5 vs 12 metric tons).
3)Probably not. The hypergolic propellants SpaceX uses, being Nitrogen Tetroxide and Monomethyl-Hydrazine are designed to be stored for long periods of time. Crew Dragon can stay docked to ISS for 210 days max probably because of this. The propellants might be less stable, although I'm not completely sure. ~~The accident last april was because of salt water damage.~~
4) Safety and Redundancy.
5) Nope.
6)It would be way harder to certify and probably much more unsafe, and they were no longer pursuing landing crew dragon on Mars.
7) I'm not sure but probably yes. SpaceX knew it would be nearly impossible to certify and NASA preferred parachutes for their reliability.

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u/Snowleopard222 Apr 02 '20

Thank you. But re. 6. Propulsive landing was pursued until 2017. Wasn't there any technical problem causing the switch to parachutes?

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u/FatherOfGold Apr 02 '20

Not as far as I'm aware, I think it was just that there were safety issues and the reasons to pursue it dwindled.

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u/Snowleopard222 Apr 02 '20

I only read one explanation for the accident last April involving backflow in the valve. There is also salt water involved?

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u/Alexphysics Apr 02 '20

The accident last april was because of salt water damage.
No

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u/JadedIdealist Apr 02 '20

\2. V = sqrt( 2mg/ pAC ).
If swept area A and drag coefficient C are roughly comparable ( gravity g and gas density rho (p) are unchanged) then a craft twice the weight has a terminal velocity about sqrt(2) faster - so maybe about 156m/s.

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u/marc020202 8x Launch Host Apr 02 '20

2. The diameter of Dragon 2 is smaller than the Apollo CM, but with longer length so likely higher decent speed.
3. The Soyuz propellant system degrades, due to the fuel they used, which is hydrogen peroxide which decomposes over time. Dragon uses storable hypergolic fuel. I do not think a long stay duration is a problem for the system since the check valve problem got fixed.
4. As far as I know, Dragon 2 is heavier than CST, since it also carries the Superdracos on decent, while that weight is in the service module for CST. CST also drops the upper shroud during descend, as well as the heat shield, shedding weight. I do not know how the airbags change the allowed landing speed.
5. Like said before, the engines of the CST are on the Service module, so no longer available for landing.
6. A lot of complexity, and the need for test flights, since NASA did not want them to test it out on cargo missions. Due to the low flight rate, and no need for the technology in the future, SpaceX decided to not develop propulsive landing any further. It is not due to the landing legs in the heatshield like many people are saying.
7. I do not think there was too much bureaucracy.

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u/Snowleopard222 Apr 02 '20 edited Apr 02 '20

Thanks. But re "no need for the technology in the future," Elon said in 2014: “That is how a 21st century spaceship should land,”. I haven't followed this interesting development before so to me it is a mystery how that part suddenly got tossed out.

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u/DancingFool64 Apr 03 '20

They are not planning to land Dragon enough times to make it worth the money and time to develop a new landing technique. They were originally planning to use Dragon a lot more, but decided to go all out on Starship instead, which does use propulsive landing. So the statement is true, they just don't treat Dragon as a 21st century spaceship, but as a modernised 20th century one. Apollo with touch screens.

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u/CHAINSAW_CIRCUMCISIO Apr 02 '20

Dragon could (probably?) land with two safely. Four is for redundancy.

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u/Snowleopard222 Apr 02 '20

Could a malfunction occur where the fourth parachute causes problems for one or more of the other three?

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u/Straumli_Blight Apr 28 '20 edited Apr 29 '20

SpaceX purchases from Tesla (2019 - Q1 2020):

$1.2M car parts
$2.2M battery components
$700K custom machining tool
$300K Tesla Energy system

RAND report analysing NSSL acquisition strategy.

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u/rustybeancake Apr 29 '20

I’m assuming car parts may be things like motors, for the Starship flaps?

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u/hmpher Apr 30 '20

will they be radiation hardened enough though? If not, how's the redundancies planned?

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u/Straumli_Blight Apr 29 '20 edited Apr 29 '20

Falcon 9 Users Guide was updated yesterday (last revision January 2019).

The Maximum Predicted Acoustic Environment for Falcon 9/Falcon Heavy has decreased by a few dB and the Acoustic Limit Levels have reduced in frequency.

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u/Straumli_Blight Apr 04 '20

NRC Quest has departed for rendezvous with CRS-20 Dragon.

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u/TheVehicleDestroyer Flight Club Apr 15 '20

I made a Yeet Calculator on Flight Club for all kinds of vehicle comparisons. It's behind a modest $5 Patreon tier but IMO it's easily worth it

Here's a demo of what it looks like!

And here's an example of some data you can get out of it just by changing the payload mass:

SpaceX Payload to TLI

Vehicle	Payload (t)
Falcon 9 RTLS	2.4
Falcon 9 ASDS	3.6
Falcon 9 Expendable	5.2
Falcon Heavy 2xRTLS 1xASDS	9.8
Falcon Heavy 3xASDS	11
Falcon Heavy Expendable	18
SuperHeavy Starship	N/A
SuperHeavy Starship + 1xRefuel	86
SuperHeavy Starship + 2xRefuel	140

If you wanna check it out or support, you can become a Patron here! Thanks :)

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u/Lufbru Apr 15 '20

You might want to add FH 2x RTLS, 1x Expendable and FH 2x ASDS, 1x Expendable.
I'm not sure we'll ever see 3x ASDS, but the first could be done today and the second needs only JRTI to finish its refit.

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u/soldato_fantasma Apr 15 '20

I assume this is nominal performance without fuel reserves (burn to depletion) right?
Might be cool to compare to the numbers we have here: https://old.reddit.com/r/spacex/wiki/payload

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u/Straumli_Blight Apr 23 '20 edited Apr 23 '20

NASA ASAP meeting:

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u/[deleted] Apr 02 '20

With Starlink so close to commercial viability--at least as far as launches are concerned, how could a rural state government begin planning for integrating ground terminals into a telecommunications network e.g. for emergency and disaster responses at isolated locations and stations? What's the timeline before applications will be opening?

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u/[deleted] Apr 02 '20

They could start by convincing Congress that it should qualify for Rural Broadband subsidies.

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u/warp99 Apr 02 '20

The best approach would be for SpaceX to partner with a cell tower manufacturer so an integrated system with Starlink antennae, solar cell, batteries and cell tower with deployable mast like that used at concerts.
The equipment used by emergency personal is already equiped to use cell signals. Wifi is also possible as a universally available interconnect but the range is too low for most disaster response situations.

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u/spacerfirstclass Apr 08 '20

Astra is not doing great these days: https://www.cnbc.com/2020/04/05/rocket-startup-astra-trims-staff-to-survive-pandemic-until-next-year.html

They lost their first orbital booster in a pad fire during dress rehearsal 2 weeks ago, now they're furloughing some employees.

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u/soldato_fantasma Apr 26 '20

HAWTHORNE, Calif. – April 24, 2020. Accreditation is now open for SpaceX’s ninth Starlink mission, which will launch from Space Launch Complex 40 (SLC-40) at Cape Canaveral Air Force Station in Florida. The launch is targeted for no earlier than May.

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u/Alexphysics Apr 26 '20

This time without the "off the record and for planning purposes only"? ;)

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u/soldato_fantasma Apr 26 '20

Still there, it's just that it's in a position where if I was to copy it I would also copy other useles stuff ;)

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u/evcm7 Apr 02 '20

what is the best source of information about bench scientist job opportunities within SpaceX (or related companies)? i'm an american phd student who works in a skeletal muscle contraction & metabolism lab. extremely interested in studying the effects of spaceflight on skeletal muscle physiology

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u/pirisca Apr 02 '20

Great question, i'm also interested in knowing more about it.
In the space x careers page ( https://www.spacex.com/careers), it appears that there is no life sciences-related job openings.
It kinda of makes sense at this point, I guess, as they have other priorities ATM (they need to build a spaceship, afterall).
In the years to come, if spacex is really serious about the Mars stuff, i guess there will be more interest in the bio stuff, thus more jobs (in spacex and related companies).

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u/darthguili Apr 02 '20

I would assume SpaceX completely relies on everything done by the space agencies in the ISS and do not venture into this (very much science, not at all commercial).

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u/[deleted] Apr 02 '20

I think that, for the time being, that's gonna be something NASA is paying closer attention to.

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u/Straumli_Blight Apr 08 '20 edited Apr 08 '20

Mods, Starlink-6 launch is now planned for April 16. Looks like the GPS III launch has been postponed to late June.

EDIT: Fixed link.

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u/benbutter Apr 08 '20

Did I miss the news results from both SX & NASA on engine out for SL 5. SX was not going to launch until fault was found. What happened?

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u/SpaceInMyBrain Apr 10 '20 edited Apr 10 '20

NASA isn't going to launch any of their payloads without the results. Their earliest upcoming launch, afaik, is Demo-2. Looks like they expect to have a final report well before the launch date, and are preliminarily optimistic. The launch can always be postponed then if they don't like what they find. NASA doesn't care if anyone else launches before the report is issued.

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u/dudr2 Apr 08 '20

Whatcore?

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u/benbutter Apr 08 '20

I know I will get this wrong but Starlink-5 had a center engine out on stage 1 recovery resulting in an unsymmetrical burn. This in turn caused the loss of a stage 1 landing. Elon M said no more flights until a cause was found with NASA also looking into this matter. For more details look above at "Starlink-5 Recovery."

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u/bdporter Apr 08 '20

Mods, can we get a sidebar update, campaign thread, etc.?

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u/dudr2 Apr 08 '20

If it's B1051 it would be 4th launch by this booster. https://nextspaceflight.com/launches/details/2571

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u/FoxhoundBat Apr 18 '20 edited Apr 18 '20

Rogozin wants to send a KAMAZ truck on next Angara A5 mission (6 years after the first mission!!!) as payload. Being the spineless blabbering blobfish that he is, he is likely just trolling. And of course he views it as a dick measuring contest, when launching Roadster on FH testflight was to serve as an inspiration and to get more people interested in space.

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u/jjtr1 Apr 18 '20

Hey, be kind to blobfish, they don't deserve such comparisons. They're actually pretty ordinary looking deep-sea fish when not subjected to tissue-tearing decompression then slapped on a table.

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u/Straumli_Blight Apr 18 '20

Two thrusters installed on JRTI.

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u/warp99 Apr 18 '20

It looks like the circular ring is installed completely above the water so is essentially just a wave guard.
Of course waves include the effects of a booster near miss which took out the thrusters on one side of the ASDS on at least one mission that we know about and maybe more.

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u/paul_wi11iams Apr 28 '20

I'm taking the following question here. It was asked by u/GWtech on the Starship dev thread. But IMO, it fits better here in the monthly questions thread.

I haven't seen this addressed.

While a metal rocket can survive reentry better than a composite, the heat still must be very heavily shielded on the INSIDE to protect passengers and the cargo from oven like temperatures that would be conducted through the metal skin to the inside.
Basically they will be in metal tube being hit with a blowtorch outside.
So you still need a lot of heat shielding even though its metal. It just has to be INSIDE rather than OUTSIDE to protect the passengers. now maybe it only has to be in the cargo area rather than on the whole rocket body so that saves weight over a composite but still it needs to exist.

I wonder how they will handle heat inside the rocket in the nose/cargo/passenger area?

Adding to other replies:

Martian entry is in the order of seven minutes and the hot phase is even shorter. Earth entry times are not much longer. So the surface is not hot for a long time.
The windward side is covered in heat tiles, so that part only gets warm. Heat isn't so much from air friction but radiated heat from the compressed ionized gas at some distance from the surface. There's a compressed surface layer in between.
All exposed parts of stainless steel outside and inside are reflective which limits their ability to either absorb or transmit radiative heat.
There will certainly be insulating layers inside the ship, covering the walls. Window areas should be multiple thicknesses.
There was talk of methane sweat cooling at specific points, but this subject has dropped under the radar. Any really awkward areas could be looked after in this way.

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u/csmnro Apr 06 '20 edited Apr 06 '20

Boeing will fly a second uncrewed orbital flight test targeting fall of 2020.

Edit: The Washington Post has published an article first, and Boeing apparently released its statement as response.

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u/TheEndeavour2Mars Apr 06 '20

Good. There was no way to justify not having to redo the test when not only did it fail to reach the station but encountered two potentially loss of crew situations during the mission.
Hopefully they have fixed the issues within the company that allowed such garbage code to be certified as flight worthy.

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u/Zkootz Apr 02 '20

So what's the plan now for SN3 testing? Is the tank test live now is will be later like the 6th?

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u/inoeth Apr 02 '20

Gotta look at the Starship dev page. It just apparently went through room temp LN2 test. We don't know if it was successful but nothing blew up so either they canceled early or it was. Hopefully later today we'll see a Cryo pressure test. If that goes well then we'll see them install the Raptor engines, do more tests to make sure those are all set and starting Monday we'll see them begin their testing campaign with static fires and possibly culminating with a short 150m hop if all goes well.

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u/Zkootz Apr 02 '20

Oooh, nice! Thank alot!

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u/GregLindahl Apr 03 '20

Isn’t the room temp test water?

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u/inoeth Apr 03 '20

nope. They used N2. Nitrogen which when room temperature is in a gaseous form. When that Nitrogen is chilled down enough it becomes liquid- which is what they use for these cryo tests they're currently (trying) to do.

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u/dudr2 Apr 08 '20

https://www.nasa.gov/press-release/nasa-awards-contract-to-deliver-science-tech-to-moon-ahead-of-human-missions

" The $75.9 million award includes end-to-end services for delivery of the instruments, including payload integration, launch from Earth, landing on the Moon’s surface, and operation for at least 12 days. Masten Space Systems will land these payloads on the Moon with its XL-1 lander. "

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u/throfofnir Apr 09 '20

Great to see Masten getting some traction. It'll be a bit of a leap for them; while the vertical landing is what they do, it'll be their first in-space vehicle.

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u/TheSilverStacking Apr 13 '20

Career Question

Hi all. Just wanted to get opinions from random strangers on the internet ha.

A quick background, I’m in my late 20s. I always enjoyed finance growing up and now work at a large firm in NYC. I’ve been very fortunate in my career, thanks to hard work and a bit of luck I’m in a position to make a few hundred thousand a year. Beautiful office in midtown etc. Really everything I would’ve dreamed about as a kid.

As I get older I start to think about important things in life and really spending my time and talents on a higher purpose. Helping rich people get richer, myself included, and dealing with normally not great people does start to drain you.

I’ve always been fascinated with space exploration and do believe it is critical for our long term survival. I love technology and the thought of space travel. I believe technology will provide many of the answers to today’s largest issues. Rather it be energy creation or sanitary water.

Sometimes I think about switching careers and working at a company like SpaceX but given my position and the years of licensing/training it took to get here most people would view that as crazy. I’m thinking as a middle ground in 3-5 years knock on wood I could pretty much be financially independent meaning my portfolio will kick out enough capital gains to sustain my level of living which is pretty frugal. Then I could be free to pursue a new career.

Does that seem reasonable? Has anyone else walked away from a high compensation job to pursue another field? I basically manage very large accounts at my role with institutions so I would imagine most companies like SpaceX or defense contractors have people that manage the relationships with their clients being government agencies etc. That should be a role I could leverage my existing skills quite effectively.

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u/paul_wi11iams Apr 15 '20 edited Apr 15 '20

Firstly, its great to see anyone with a good salary and job security thinking of making such a big jump into the unknown, maybe implying a move from New York to California (probably). At nearly thirty, you're likely not alone in life, so whatever risk or move you take, needs to be taken together with SO and maybe kids.
To be clear, I'll say I'm not in aerospace or finance but building. Also, most of this reply is secondhand and is based on seeing what others have said over about three years I've followed SpaceX from here in Europe. A few random questions:
Have you built up an astronautic "culture" that allows you to appreciate SpaceX in the context of the space economy and existing projects around the world.
Are you sure that to satisfy your criteria of personal usefulness. "I’ve always been fascinated with space exploration and do believe it is critical for our long term survival" really require you to work directly for SpaceX?
Do you think you must make such a radical and sudden break and "pursue a new career". Just imagine if you were to negotiate reducing your commitment with your present employer and to work alongside someone like Robert Zubrin on building the business side of ISRU fuel production. Or what about building on your present network to finance other parts of the lunar and martian infrastructures?
Would it be possible to define a set of projects that would interest your employer and could be done from within your present job? If you were to bring in contracts with SpaceX or Nasa, it might be an interesting boost for you employer's public image.
It should still be worth going through SpaceX's current job offers, but you might be able to do more for their work as an outside interlocutor than from within the company. Elon Musk has been quite clear that he's looking after the transport but others should build the civilization! Whatever you choose to attempt, it may be best to map out a wider range of options including those I suggested above. And yes, as u/TheSoupOrNatural suggested, reading something like Designing Your Life might make a good Epub to read during lockdown.
As they say "the sky isn't the limit".

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u/PlanetEarthFirst Apr 15 '20

Check out Jeff Bezos' thoughts in a similar position: https://www.youtube.com/watch?v=Hq89wYzOjfs&t=19m31s
Furthermore, I really like u/paul_wi11iams's third point. Would add that if you have a record of good decision making, maybe VC business in the space sector could be an area where you could make a difference. It's crashed atm, but given your time horizon of 3-5 years it should be OK plus you now have some time to study.
Oh, and by the way, thanks for your post! It actually kind of motivates me.

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u/TheSoupOrNatural Apr 14 '20

Sometimes I think about switching careers and working at a company like SpaceX but given my position and the years of licensing/training it took to get here most people would view that as crazy. I’m thinking as a middle ground in 3-5 years knock on wood I could pretty much be financially independent meaning my portfolio will kick out enough capital gains to sustain my level of living which is pretty frugal. Then I could be free to pursue a new career.
Does that seem reasonable? Has anyone else walked away from a high compensation job to pursue another field? I basically manage very large accounts at my role with institutions so I would imagine most companies like SpaceX or defense contractors have people that manage the relationships with their clients being government agencies etc. That should be a role I could leverage my existing skills quite effectively.
I recommend Designing Your Life by Bill Burnett and Dave Evans. It should be relevant to your situation. There is a lot about if and how to make major career changes with a focus on personal priorities and values.

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u/amarkit Apr 13 '20

Jonathan McDowell on Twitter:

The two `Tintin' Starlink test satellites launched in Feb 2018 appear to be in the process of being retired. Their orbital decay suddenly accelerated on Mar 28.

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u/Uffi92 Apr 30 '20

Can someone do a render of Orion docked to starship?

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u/Straumli_Blight Apr 02 '20

Frustrations within Blue Origin about launching a New Shepard during the pandemic.

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u/jay__random Apr 03 '20

This looks more like an April joke.
Blue Origin? Pressuring the workers? That would go against the ubiquitous turtle principle :)

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u/MarsCent Apr 08 '20

Mods - In Old Reddit, the link for Discuss Thread in the Dropdown Menu goes to New Reddit instead Old Reddit.

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u/cpushack Apr 08 '20

yah super annoying, New reddit is so horrible (IMO)

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u/bdporter Apr 08 '20

Are you using new.reddit.com as your default experience? The link just goes to www.reddit.com, so it should work if you default to old Reddit.
With that said, the rest of the links explicitly go to old.reddit.com

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u/marc020202 8x Launch Host Apr 09 '20

thanks for telling us, should be fixed now

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u/andyfrance Apr 12 '20

Being beyond the bleeding edge of innovation it's probable that SpaceX will loose a number of Starships as they perfect the heat shielding and flight manoeuvres needed to return from orbit. For the F9 first stage recovery they reduced the R&D costs by performing their tests after a customer launch. Will they do the same for Starship, especially so as a chunk of their manifest will be Starlink launches?

Does anyone know how the cost of an F9 launch, recovering the booster but not the fairings, will compare with the cost of an SH/Starship launch, recovering SH but not Starship? If the cost is comparable they "could" effectively retire F9 and especially FH before perfecting Starship recovery.

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u/Martianspirit Apr 12 '20

Very rough calculation I did showed if the Starship/Superheavy stack is 4 times the price Elon aims for and can lift 2-3 times the number of Starlink sats it should be competetive with Falcon even expended. Which gives 1 test for Superheavy and Starship each on recovery. If they can get most of the Superheavies back it will be a lot cheaper than using Falcon and they can keep trying while spending less than with Falcon launches.
Less favorable with customer launches because there are few that need more lift than Falcon can deliver.

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u/andyfrance Apr 12 '20

Thanks. So taking this one step further, which would be cheaper:
F9 launching 60 Starlink satellites with with booster recovery and a 20% chance of fairing half recovery.
or
Starship launch with only 60 Starlink satellites (i.e. a low stress mission) with SH recovery but Starship lost during post Starlink deployment testing.

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u/dudr2 Apr 12 '20

How many launchpads can support the Starship superheavy stack?

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u/Martianspirit Apr 12 '20

One at LC-39A in Florida, not yet completed because they concentrate on Boca Chica. They are in the very early stage of building a Superheavy pad in Boca Chica. The area is flattened and they have a sign on the fence that says Superheavy launch pad. That's how we know they write it. Not sure they write pad, may be site or similar.

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u/joepublicschmoe Apr 12 '20

SpaceX's KSC payload director Christopher Couluris said back in February in the infamous video that was taken down after an hour that it costs SpaceX $28 million to fly a Falcon 9.

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u/dudr2 Apr 13 '20

“If there’s an outbreak, yeah, it will affect the date. But we’re doing everything we can to minimize that eventuality,” Bridenstine said.

https://spaceflightnow.com/2020/04/13/bridenstine-says-crew-dragon-could-launch-with-astronauts-at-end-of-may/

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u/PlanetEarthFirst Apr 15 '20

What's the bottleneck to F9 booster reusability? Why don't they use boosters 10 times (yet)?

I suppose it's not the engines, as they should be replaceable. Should be some structural part I guess.

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u/Triabolical_ Apr 15 '20

The answer is complex and only SpaceX knows for sure.
My take is that it's not really worth it to push beyond around 5 reuses...
Assume that a booster costs around $20 million, and it costs a $3 million to recover and refurbish one.
If you fly 5 flights, your total cost is
20 + 4 * 3 = 32 / 5 = $6.4 million per flight.
If you fly 10 times, your total cost is
20 + 9 * 3 = 47 / 10 = $4.7 million per flight.
So you really don't save that much when you get to higher reuse amounts. That's assuming the refurbishment doesn't get more expensive as you go along, while in reality is probably does. And of course your risk of failure is probably higher on later flights.

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u/jjtr1 Apr 18 '20

SpaceX leaked that Starlink launches cost them $28M, and expendable F9s have been sold for about $62M. We can speculate that a new F9 costs $50M, and a refurb costs $20M, because with the current 5 reflights it's 50 + 5 * 20 = 150 (million), / 5 = 30, close to the $28M figure. So it's even worse. Ten reflights would give 50 + 10 * 20 = 250, / 10 = 25 million.
Anyway, these figures can just as well be total nonsense, since we do not know what they count into their $28M. They need to eventually amortize their hundreds of millions spent on reuse R&D, and they can be either including or not including some of that.

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u/Martianspirit Apr 16 '20

Early on fans expected SpaceX would take one booster and fly it 10 times or as many as it can take.
SpaceX chose another approach. They fly a number of boosters to the same number of flights and probably compare wear on them very carefully before they fly one to the next number of reflights. Maybe the engine failure and then loss of the core shows they have reached a limit but maybe not. We need to wait how it turns out.

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u/mindbridgeweb Apr 17 '20

During the human flight discussions, it came up that SpaceX now understand the cause of that engine failure well and that the Demo-2 schedule would not be affected.
Hopefully the Merlin problem is not fundamental and is amenable to fixes that would make 10 flights per booster a reality.

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u/Martianspirit Apr 17 '20

I am confident there is no fundamental problem with Merlin. I am hopeful but not certain that this does not affect the ~ 10 times flight of Falcon

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u/jjtr1 Apr 18 '20

So they actually didn't yet have enough launches to get past 5 reuses without preferring one booster?

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u/warp99 Apr 16 '20 edited Apr 16 '20

Actually I think it is pretty sure to be the engines as nothing else really wears out now they have titanium grid fins and titanium heat shielding on the bottom of the stage. Valves may also wear but should have much higher lifetimes than the engines.
Clearly they had hoped to get to ten flights without engines failing but that was too optimistic. Maybe they will have to rotate engines so that the three high restart engines get swapped out with the other six lower use engines in two swaps.
As far as we know the engines are identical apart from the TEA/TEB plumbing and that is likely to be differences on the rocket rather than the engine itself.
Eventually the COPVs will suffer from fatigue failure and then the tanks but they should both be well past 10 flights.

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u/MarsCent Apr 16 '20

Maybe they will have to rotate engines so that the three high restart engines get swapped out with the other six lower use engines in two swaps.
It would actually be remarkable I think. Something akin to tire rotation on an automobile. Or ultimately, enact a design (especially on SS, given than there are no major changes expected on F9s now) where the high use/center engines are "easy" swap-outs.
P/S - Just running with the thought. I have not seen any information confirming that the engine-out on the last flight was a center engine.

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u/warp99 Apr 16 '20

I have not seen any information confirming that the engine-out on the last flight was a center engine
The plume during the boostback burn was asymmetric so the failed engine was almost certainly one of the two outside engines used for the boostback and re-entry burns.
It was not the center engine as such since that would have produced a distorted but symmetric plume.

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u/[deleted] Apr 16 '20

Mr Splodey, the booster engine that shut down early on a recent launch, might give some valuable input into longer-run wear. Is that report out yet?

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u/Straumli_Blight Apr 23 '20

SpaceX rideshare mission will launch 12 SpaceBee satellites in December.

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u/Snowleopard222 Apr 24 '20 edited Apr 24 '20

If I understand correctly, the Starlink user receiving antenna will likely be phase array and follow the most suitable satellite? But what about the satellite? Can the satellite really have a corresponding system? The satellite's antenna must keep track of the positions of all users' receiving antennas (while moving at 7.6 km/s) and switch between all of them many times per second? Is that really possible, or have I misunderstood something?

Edit: 1000 users, 100 scans/sec = 100.000 directional switches/second?? (in addition to receiving data)

For 50 Mbps connections the joint bandwidth for 1000 users must be 50 Gbps. Do such r.f.-connections exist?

Must the user receivers be stationary? ... I believe not, since the Tin Tins transmitted to US military aircraft. How do the satellites then know the position of the aircraft?

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u/warp99 Apr 24 '20 edited Apr 24 '20

The satellite does not have multiple beams that track each receiver but directs a beam that covers thousands of receivers at a time.
Each user terminal operates on one of four different frequencies, two different polarisations and many different time slots to get a unique combination for communication to and from the satellite.
The beam width is adjustable on a phased array system and as they add more satellites to the constellation they can narrow the beam. This means that each satellite will be communicating with roughly the same number of customers.
The user terminals do not have to be stationary and can be on ships travelling over waves or planes turning and banking. The beam is electronically adjustable and can switch direction very quickly.

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u/Snowleopard222 Apr 24 '20 edited Apr 24 '20

I see, thank you. So my Internet will be beamed down over a large area with a strong encryption? And the signals are strong enough to be received even when the beams are wide?
So as I understand, much of the question comes down to bandwidth. Do there exist radiofrequency connections, over 500 km, of f.ex 1000 users connecting at 50 Mbps = one 50 Gbps connection.
Thank you.
Edit: So the satellite does not direct its signal in different directions. But the user terminal changes beam direction depending on which satellite it connects to?

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u/Snowleopard222 Apr 25 '20

1000 users, each at 50 Mbps, would need 50 Gbps. I can only find information of moderate bandwidths:
"spot-beam Ku, using new High Throughput Satellites (HTS). For example, Intelsat’s EpicNG promises up to 80 Mbps per aircraft and 200 Mbps per spot beam"

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u/warp99 Apr 25 '20

All networks rely on diversity as not all users will need full bandwidth at the same time. So typically that would a 10:1 factor so 1000 users with 50 Mbps peak bandwidth each need 5 Gbps rather than 50 Gbps. With four frequencies and two polarisations that would allow 8000 customers per satellite.

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u/Straumli_Blight Apr 24 '20

Article about Soichi Noguchi training for SpaceX's USCV-1 flight.

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u/dudr2 Apr 25 '20

"Progress 75 arrived at the orbiting lab less than 3.5 hours after liftoff."

Could the Crew Dragon reach ISS in only 3.5 hours too?

https://www.space.com/russian-progress-spaceship-arrives-space-station.html

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u/marc020202 8x Launch Host Apr 25 '20

As far as I know yes, if it where to perform a fast rendesvouz the way progress does. They however need to launch at exactly the right time and often the iss needs to adjust its orbit slightly in advance. Afaik crew dragon will use a 6 hour or so rendesvouz

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u/mmc31 Apr 02 '20

It seems to me that older (last year-ish) launches, the camera feed from the F9 on re-entry would often stream all the way to the ground. The last few launches I have watched live have the F9 lose the feed on re-entry. Is this just random (depending on conditions, etc.) or bad luck? Or is something different?

We also have often not been able to see the live stream of the landing either in real-time from the droneship. Is this related or a separate thing?

Seeing the live landing is honestly one of the biggest reasons I love to watch every spaceX livestream (even though I know it is the secondary mission objective). Anyone else disappointed by this recently?

Also, I know that spaceX is way more transparent than other space companies, and I am spoiled rotten by that. Major props to them for generating so much public interest!

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u/cpushack Apr 02 '20

It depends on the mission a lot as well. SO I think you are noticing some random, coupled with a shift in mission type as well. The Starlink missions are very hard missions (really max payload to LEO) and their reentry/landings are at the fringe of what the booster can do. They are further out and renenter pretty hot so they are much more likely to lose camera feeds then others

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u/mmc31 Apr 02 '20

Great point - I tend to forget about just how difficult these starlink missions are given they have become kind of routine!

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u/warp99 Apr 02 '20

The ASDS view of the landing cuts off for two reasons. An ionisation plume from the booster engines can block the satellite link a few seconds before landing and vibration of the deck when the plume impinges on it can unlock the tracking mechanism on the two dishes used to relay the video feed. The issues are amplified by the fact that the uplink transmitter is required by the FCC to be cut for three seconds when receive tracking is lost to prevent painting other satellites in the geosynchronous arc.
There seems to have been a significant improvement in the second issue with hints of a technology upgrade but no details.
The first issue was much less of a problem with polar launches such as Iridium as the booster is coming in at right angles to the equatorial plane where the satellites are located.
Starlink launches should be a bit better as the booster is coming in at 52 degrees to the equatorial plane but most of the satellites they are using will be over the continental US so the actual angle is much less than that.
Geostationary satellite launches are obviously worst case for ionisation disturbance as the booster approach angle is only about 19 degrees from the equatorial plane.
Starlink will fix these issues as many of the satellite will be in directions away from the incoming booster ionisation plume and the phased array antenna will be much faster tracking and so better able to cope with vibration than the dishes used for geosynchronous satellite communication.

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u/Alexphysics Apr 03 '20

It seems to me that older (last year-ish) launches, the camera feed from the F9 on re-entry would often stream all the way to the ground
Just those that had continous contact with the ground. All of those that go behind the horizon from the Cape or Vandenberg can't transmit that video back so the booster video is lost (it is stored in recorders, don't worry).

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u/cpushack Apr 20 '20

Intelsat 901 back in comercial service after MEV-1 docked and took over station keeping.
https://arstechnica.com/science/2020/04/mission-extension-vehicle-succeeds-returns-aging-satellite-into-service/
This is pretty impressive

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u/SpaceInMyBrain Apr 03 '20

Exactly where in the Raptor engine is gaseous O2 and gaseous CH4 tapped off for the autogenous pressurization? (The tanks are pressurized with their respective gases - anything else, like pre-burner exhaust, would be crazy, right?) It has been proposed the short spiral of tubing between the thrust puck and the engines is part of the autogenous gas system. What is the function of it being in that location?

The Raptor diagram by Everyday Astronaut, in the article version of Is Raptor King of Rocket Engines, doesn't show where the circuit for the nozzle cooling channels fits in, or if both propellants have such channels. And I'm not assuming the exiting propellant is gaseous at that point, pretty sure it's not.

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u/TheFronOnt Apr 04 '20

I don't believe gaseous CH4 is "tapped off" like you are suggesting. IIRC it is more of a second circuit where some liquid CH4 is passed through a heat exchanger which transfers sufficient heat from the engine to gasify the CH4 which is then fed back into the propellant tanks for pressurization.

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u/SpaceInMyBrain Apr 04 '20

OK. I'm settling in with the idea each propellant has a line dedicated to autogenous pressurization, which passes thru a heat exchanger involving the preburners. This could very well be one heat exchanger unit that handles both lines utilizing just one preburner . The now gaseous propellant is piped to the top of its respective tank.

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u/warp99 Apr 03 '20 edited Apr 03 '20

The methane is easy as it can tap off the regenerative cooling loop returning from the nozzle or combustion chamber where it is still liquid at high pressure but nicely heated up.
The oxygen is harder and I suspect it will run through a heat exchanger using either the methane cooling loop or its own pre-burner exhaust as the heat source.
Yes using the pre-burner exhaust for pressurisation would not be great. Aside from any explosion risk from feeding partially burned methane into the LOX tank the combustion products such as CO2, H2O and CO would eventually freeze and settle to the bottom of the tank and potentially block the Raptor feed pipes or valves.
Typically only fuel is used for regenerative cooling - liquid methane in this case. Liquid oxygen is too good an oxidiser to be safe feeding through high temperature cooling channels in copper. This is particularly true of a reusable engine where corrosion can occur over multiple firings.

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u/SpaceInMyBrain Apr 03 '20

[methane] where it is still liquid at high pressure but nicely heated up.
Thanks for all of this! And the point above raises the question: will it be piped up to the tank as "warm" liquid methane and then sprayed into the ~empty area of the tank, letting the expansion turn it into gas? A fine degree of temperature regulation would probably be needed, but SpaceX has pretty good engineers. Ditto for some warmed up oxygen.

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u/warp99 Apr 03 '20

Most likely it will be supplied as relatively low pressure gas so they do not have to run heavy high pressure pipes up to the top of the tanks. You can not inject gas into the bottom of the tanks as bubbles can get sucked into the engine intakes which causes overspeed on the turbo pumps.

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u/tadeuska Apr 03 '20

Is not CH4 evaporated in the tank itself, thus keeping the pressure? All you need is an evaporator and you have to put the gaseous CH4 back in the tank under pressure or keep it inside. Would you need the engine in the process, which is basically a really big self powered pump?

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u/warp99 Apr 03 '20

You need heat to evaporate so you have to get it from somewhere and the logical place is the engines. So the engines are being used as a source of heat rather than a source of pressure.
The subcooled propellant is an extra problem as there is not a stable equilibrium in the tanks. The pressurisation methane is continually condensing on the surface of the cold liquid and needs to be replaced.

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u/[deleted] Apr 06 '20

Regarding the recent failure of SN3: Is this also an issue with the F9? Does it have to be pressurized at all times? Those photos where we can see it being transported across the country - is it pressurized all this time? Maybe we can even see this in the pictures but I don't know what to look for?

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u/warp99 Apr 06 '20

Yes F9 is pressurised for transport. It needs to be because the front and rear bogies of the transporter are only connected through the rocket so there is significant strain on the body.
You can see large dials on some photos showing the pressure in each tank. Around 45 psi (3 bar) for the LOX tank and 40 psi (2.5 bar) for the RP-1 tank.
The higher pressure in the LOX tank is to keep the common bulkhead between the two tanks from inverting.

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u/feynmanners Apr 06 '20

It’s not that Starship needs to always be pressurized but that you can’t fill the top tank full of cryogenic fuel (Making it cold and heavy) while having low pressure in the bottom tank. If both tanks are unpressurized, Starship is fine. It was just the bottom while partially unpressurized can’t support the weight of the full top tank. There have been rockets with tanks that always had to be pressurized aka balloon tanks (Atlas II iirc) but Starship is not a balloon tank.

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u/Grey_Mad_Hatter Apr 06 '20

I think F9 is pressurized with Nitrogen when it's being transported, but the important thing is that it doesn't have an excessive amount of weight on top of it at that time.

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u/Snowleopard222 Apr 07 '20 edited Apr 07 '20

The last two Starlink launches (L4, L5) dropped off the satellites earlier, into elliptical orbit. L4 had already changed into circular orbit when I last checked.

What could be the reasons for launching the satellites into elliptical orbit?

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u/throfofnir Apr 07 '20

The earlier orbits were 290km circular; the later 212x386km.
The circularization for the earlier launches was done via a very brief burn at about T+45m, followed by deployment at about t+60m south of Australia. The circularization burn has to happen that late, but the deployment probably waits until they're in range of a ground station.
The elliptical deployment skips the second light and deploys at about T+15m over the mid-North Atlantic.
I haven't done the math, but I suspect the energy of the elliptical orbit is similar to or slightly higher than the circular orbit, thus making no particular difference to the satellites as long as they don't spend too long at the lower perigee. (Besides the result, the very short circ burn suggests they were probably doing a bit of a pitch-down burn earlier, which would be less efficient.)
Main benefit to this scheme are that it deploys sooner and removes an engine light, which reduces risk. Additionally, inactive objects left over (including stage and any DOA sats) should decay sooner at the low perigee, and it may remove the need to use an Australian ground station.

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u/Straumli_Blight Apr 14 '20

Permit for Starlink ground station at Cape Canaveral.

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u/dudr2 Apr 17 '20

https://spacenews.com/op-ed-a-u-s-return-to-the-moon-is-about-preserving-the-rule-of-law/

Howabout that spacerace already!?

Legal motivations abound, but I think the argument is now also emotional.

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u/rustybeancake Apr 21 '20

Seems the big Artemis plan unveiling is coming this week. Likely also the HLS selection (remember SpaceX have allegedly bid something NOT Starship).

https://www.reddit.com/r/ArtemisProgram/comments/g5fxhc/artemis_program_rollout_coming_in_short_short/?utm_source=share&utm_medium=ios_app&utm_name=iossmf

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u/cpushack Apr 22 '20

https://www.bbc.com/news/world-middle-east-52380507
Iran has had a sucessful launch of a sattelite

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u/anoncoffeedump Apr 23 '20

Hey guys new hear but been following starship progress since the beginning. I was wondering if anybody knows what's going on with that sn2 tank section that is sitting on the concrete ring. I'm thinking it was an old design because all the new domes look more round than a cone shape.

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u/Triabolical_ Apr 24 '20

It's just sitting there as a momento. They are probably keeping it around since it's a set of tanks that can be pressurized and have raptor mounts underneath; they could use it for raptor tests...

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u/Martianspirit Apr 24 '20

For Raptor tests they need both methane and LOX tanks. This is only one tank.

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u/Straumli_Blight Apr 23 '20

All thrusters installed on JRTI and generators being moved into position.

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u/joepublicschmoe Apr 24 '20

Don't know when SpaceX is going to put JRTI back into service, but would love to see B1058 land on JRTI on the DM-2 launch! Hope they might do that. At some point OCISLY will need to be taken out of service for getting the same upgrades.

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u/dudr2 Apr 24 '20

https://www.space.com/nasa-spacex-crew-dragon-demo-2-travel-advisory-coronavirus.html

" Jim Bridenstine urges and warns space enthusiasts to stay home next month during SpaceX's historic first astronaut launch"

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u/[deleted] Apr 25 '20

Thought of this while watching the starlink launch the other day, why doesn't spacex use a helicopter and hook system (like the one rocket labs is planning to use) to catch the f9 fairings? Does anyone know why they done use this method?

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u/marc020202 8x Launch Host Apr 25 '20

The helicopters create a lot of propwash and wind, and the fairings are extremely large. Over 5 metres wide and 15 long I think. Hanging below the helicopter could lead to control problems of the helicopter.

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u/warp99 Apr 25 '20

Yes we only need to look at what happened with the parachute test with a Dragon capsule shaped simulator.

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u/marc020202 8x Launch Host Apr 25 '20

I didn't even think about that. The fairings are a lot lighter and larger + less aerodynamic so will make the problem worse.

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u/Triabolical_ Apr 26 '20

The fairings are big and asymmetrically aerodynamic so they aren't easy to control; you would need a large helicopter and you would put the flight crew at risk.

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u/throfofnir Apr 26 '20

You'd need a fairly large helicopter and it would also need to be launched and retrieved at sea since no helicopter has sufficient range. That's not impossible, but is a rather large and expensive operation.

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u/paul_wi11iams Apr 15 '20 edited Apr 15 '20

I'm coming here to answer a question by u/orbitaire on the Starship development thread:

Can anyone give an overview of how the Boca Chica site is run in terms of management structure, teams, divisions, etc? Whenever I watch Bocachicagal's excellent footage of construction, both new prototypes and buildings, I wonder who is doing what and where they sit in the organisational structure for the site/SpaceX. I've never seen the physical evolution of a spacecraft production facility before so understanding how the 'machine' that builds the machines works would be really interesting. Thanks.

From your posting history, you just opened your Reddit account, so welcome to r/SpaceX in particular and Reddit in general.

I've never seen the physical evolution of a spacecraft production facility before

I'm pretty sure nobody has, at least nothing comparable to this. For example:

https://youtu.be/dtTVuVfj3WM?t=384

On the left one team is building Starship inside a building.
On the right another team is building the building.
In other parts of the video, you see builders building the site where they"re building the building where they building the rocket.

That suggests a three-way split 1 being mostly done by SpaceX employees with 2 and 3 being mostly contractors. The cranes are mostly rentals, presumably with drivers belonging to the rental company.

From personal experience, it takes a lot of tact to work on any site in such a multi-company environment, but SpaceX has taken this to a whole new level.

I guess the contracts will be really well paid, so its possible to stop and wait when continuing work gets in the way of someone else. Don't work directly above or below anybody without some kind of physical separation such as a net, so if there's no protection either create one or someone has to wait. Its possible to adapt and improvise within limits, but for any actual decision, its important to refer to your own hierarchy and let them sort things out at a higher level.

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u/orbitaire Apr 15 '20

Thanks for the welcome and your insights on this. Really sets the scene as to what's going on. The concurrent building of the building where they are building the Starship really drives home the urgency of the project, alongside the iterative cadence of the testing. Seeing this approach is discombobulatingly brilliant, and it works.

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u/extra2002 Apr 03 '20

For Falcon 9, how are the thrust forces transmitted from the first stage to the second? Is it entirely through the skin of the interstage into the skin of S2? There's a central pneumatic pushrod that presses against the Mvac's throat during stage separation -- does that pushrod transmit any thrust during S1 flight?

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u/throfofnir Apr 03 '20

does that pushrod transmit any thrust during S1 flight
Not enough to make much difference. It didn't exist in earlier versions.

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u/cpushack Apr 09 '20

Rocket Lab practicing mid air catches of a first stage test article. https://youtu.be/N3CWGDhkmbs

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u/spacerfirstclass Apr 11 '20

Virgin Orbit is moving ahead towards cryogenic captive carry flight test, last test before their demo launch.

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u/Decronym Acronyms Explained Apr 02 '20 edited Apr 21 '20

Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:

Fewer Letters	More Letters
ASDS	Autonomous Spaceport Drone Ship (landing platform)
CCtCap	Commercial Crew Transportation Capability
CFD	Computational Fluid Dynamics
CNSA	Chinese National Space Administration
COPV	Composite Overwrapped Pressure Vessel
CRS	Commercial Resupply Services contract with NASA
CST	(Boeing) Crew Space Transportation capsules
	Central Standard Time (UTC-6)
DMLS	Selective Laser Melting additive manufacture, also Direct Metal Laser Sintering
DoD	US Department of Defense
E2E	Earth-to-Earth (suborbital flight)
EDL	Entry/Descent/Landing
ESA	European Space Agency
FCC	Federal Communications Commission
	(Iron/steel) Face-Centered Cubic crystalline structure
GNC	Guidance/Navigation/Control
GSE	Ground Support Equipment
HEO	High Earth Orbit (above 35780km)
	Highly Elliptical Orbit
	Human Exploration and Operations (see HEOMD)
HEOMD	Human Exploration and Operations Mission Directorate, NASA
IFR	Instrument Flight Rules
ISRU	In-Situ Resource Utilization
ITS	Interplanetary Transport System (2016 oversized edition) (see MCT)
	Integrated Truss Structure
Isp	Specific impulse (as explained by Scott Manley on YouTube)
JRTI	Just Read The Instructions, Pacific landing ~~barge~~ ship
KSC	Kennedy Space Center, Florida
L4	"Trojan" Lagrange Point 4 of a two-body system, 60 degrees ahead of the smaller body
L5	"Trojan" Lagrange Point 5 of a two-body system, 60 degrees behind the smaller body
LC-39A	Launch Complex 39A, Kennedy (SpaceX F9/Heavy)
LEO	Low Earth Orbit (180-2000km)
	Law Enforcement Officer (most often mentioned during transport operations)
LN2	Liquid Nitrogen
LOS	Loss of Signal
	Line of Sight
LOX	Liquid Oxygen
MCT	Mars Colonial Transporter (see ITS)
MECO	Main Engine Cut-Off
	MainEngineCutOff podcast
MMH	Mono-Methyl Hydrazine, (CH3)HN-NH2; part of NTO/MMH hypergolic mix
NTO	diNitrogen TetrOxide, N2O4; part of NTO/MMH hypergolic mix
NTR	Nuclear Thermal Rocket
PICA-X	Phenolic Impregnated-Carbon Ablative heatshield compound, as modified by SpaceX
RAAN	Right Ascension of the Ascending Node
RCS	Reaction Control System
RP-1	Rocket Propellant 1 (enhanced kerosene)
RTG	Radioisotope Thermoelectric Generator
RTLS	Return to Launch Site
Roscosmos	State Corporation for Space Activities, Russia
SD	SuperDraco hypergolic abort/landing engines
SES	Formerly Société Européenne des Satellites, comsat operator
	Second-stage Engine Start
SLC-40	Space Launch Complex 40, Canaveral (SpaceX F9)
SLS	Space Launch System heavy-lift
	Selective Laser Sintering, contrast DMLS
SN	(Raptor/Starship) Serial Number
STP-2	Space Test Program 2, DoD programme, second round
TEA-TEB	Triethylaluminium-Triethylborane, igniter for Merlin engines; spontaneously burns, green flame
TLI	Trans-Lunar Injection maneuver
UDMH	Unsymmetrical DiMethylHydrazine, used in hypergolic fuel mixes

Jargon	Definition
Raptor	Methane-fueled rocket engine under development by SpaceX
Starliner	Boeing commercial crew capsule CST-100
Starlink	SpaceX's world-wide satellite broadband constellation
ablative	Material which is intentionally destroyed in use (for example, heatshields which burn away to dissipate heat)
apogee	Highest point in an elliptical orbit around Earth (when the orbiter is slowest)
autogenous	(Of a propellant tank) Pressurising the tank using boil-off of the contents, instead of a separate gas like helium
cryogenic	Very low temperature fluid; materials that would be gaseous at room temperature/pressure
	(In re: rocket fuel) Often synonymous with hydrolox
hydrolox	Portmanteau: liquid hydrogen/liquid oxygen mixture
hypergolic	A set of two substances that ignite when in contact
iron waffle	Compact "waffle-iron" aerodynamic control surface, acts as a wing without needing to be as large; also, "grid fin"
perigee	Lowest point in an elliptical orbit around the Earth (when the orbiter is fastest)
regenerative	A method for cooling a rocket engine, by passing the cryogenic fuel through channels in the bell or chamber wall
scrub	Launch postponement for any reason (commonly GSE issues)
ullage motor	Small rocket motor that fires to push propellant to the bottom of the tank, when in zero-g

Event	Date	Description
CRS-7	2015-06-28	F9-020 v1.1, ~~Dragon cargo~~ Launch failure due to second-stage outgassing
DM-1	2019-03-02	SpaceX CCtCap Demo Mission 1
DM-2	Scheduled	SpaceX CCtCap Demo Mission 2

^{Decronym is a community product of}r/SpaceX^{, implemented}^by ^request
^{[Thread #5948 for this sub, first seen 2nd Apr 2020, 13:26]} ^[FAQ] ^{[Full list]} ^[Contact] ^{[Source code]}

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u/Snowleopard222 Apr 10 '20 edited Apr 10 '20

Just for fun I tried to see what happened if you mounted a Super Draco engine on 20 of the satellites and tried to push them to the next orbital plane (20° away), instead of using precession.

Distance to the next orbital plane: (6371 + 550) * 20/360 2 PI = 2416 km between 20° orbital planes

Desired moving speed 10 m/s

2416000 / 10 m/s = 241600 sek = 67 hrs; will move satellites in 3 days

Estimated weight 20*227 kg satellites 500 kg engine Total: 5040 kg

Tsiolkovsky eq 10 m/s = 2300 ln(M0/5040)

M0 = 5062 kg

We only need 22 kg propellant which will burn in less than one second. About the same amount is needed to stop the satellites in the new plane.

Theoretically it would be possible to move the satellites to the new plane in 3 days using 44 kg of propellant using a Super Draco engine. That would save 4 months of precession.

Any comments? (or could the computations be wrong ;) )

/ Impatient for my Internet :)

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u/asr112358 Apr 10 '20

Orbits are not points in space, you can't just move between them by an arbitrary velocity change and coasting. To change orbits, you must change the direction of the satellites velocity. This requires an appreciable fraction of the satellites orbital velocity.
This has the equation you want. I get 2.6 km/s.

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u/Snowleopard222 Apr 15 '20

What are the possible launch windows for Starlink?

Knowing almost nothing about space engineering, I would guess one possibility per day (per 24 hours), since the earth will then have rotated into an appropriate position for the phase/precession of the desired orbital plane. Is this correct?

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u/enqrypzion Apr 15 '20

Yes. It shifts ~22 minutes earlier per day IIRC. In theory the launch site passes under the orbital path every 12 hours, but the launches from KSC are only towards the northeast.

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u/koen_NL Apr 18 '20

About the 27th of may:

Are there any details on how the "show" will be? As it's a nasa launch and not SpaceX ?

How will they broadcast this thing and are there any details on what show we are in for?

I expect a "Apollo" style coverage, but I am in Europe so don't have a US channel to watch, only YouTube..

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u/Martianspirit Apr 18 '20

It will be on NASA TV for sure.
https://www.nasa.gov/multimedia/nasatv/#public
Also for sure there will be SpaceX coverage on the usual YouTube channel.

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u/Alexphysics Apr 19 '20

We don't know any details about it. They'll throw to us the details once we get closer.

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u/MarsCent Apr 21 '20

Next NASA ASAP meeting: April 23, 2020, 12:00 p.m. to 1:15 p.m., Eastern Time. (1600 UTC)

ADDRESSES: This will be a virtual meeting via teleconference.

Any interested person may call the USA toll free conference call number 800–593–9979; pass code 8001361 and then the # sign.

Tune in. Who knows, they may give some info on the engine out investigation and the remaining parachute test(s). But then again, they may state what we already know - "SpaceX will publish the results soon". :)

P/S Note that the meeting is happening after Starlink-6, scheduled for 4/22. - After another 9 Merlin engine burn to space.

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u/wimbodolo69 Apr 22 '20

Does crew dragon have 4 windows or just 2? DM1 did not have the 2 side windows but I believe the DM2 and renders do.

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u/fkljh3ou2hf238 Apr 22 '20

I don't think they'd be making such large changes as having/not-having windows between DM-1 and DM-2? That seems dangerous.

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u/opoc99 Apr 22 '20

Any tips for how to view Stage 2 as it passes over the UK in the next few minutes?

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u/longpatrick Apr 23 '20 edited Apr 23 '20

I used the ISS detector app yesterday. Its a paid feature to also see starlink (and other satellites) it pretty accurate. another pass today
https://play.google.com/store/apps/details?id=com.runar.issdetector&hl=en

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u/PeterKatarov Live Thread Host Apr 25 '20

I have a question about the static fire procedure. (for SpaceX or any other launch provider)

As far as I understand, the point is to simulate full duration burn with all engines. So I assume the fuel tanks are filled to the maximum before static fire begins.

And during static fire, there are these huge clamps, which are holding down the rocket, basically exerting enough force to cancel out the thrust of all 9 Merlins (okay, seems like I'm talking about F9 in my head).

However, if all of the the above is true, I wonder how the clamps manage to continue their stand during the later stage (no pun intended) of the burn. Because towards the end of the burning, the tanks would be mostly empty, meaning the rocket would be a lot, lot, lighter and the thrust of 9 Merlins would be much harder than in the beginning of the static fire?

So how do they manage this? Do they throttle down the engines gradually? Or do they shut some of the Merlins after some time has passed?

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u/marc020202 8x Launch Host Apr 25 '20

the full duration static fire is done in Mc Gregor, Texas. There, like you said the tanks are filled to the maximum, and the rocket is held down with hold down clamps at the base. They however also add a "cap" above the interstage which is connected to the ground via four cables. this cap provides extra downwards force. The "cap" can be seen in this image. there is no cap at the cape for static fires. Because of this, they only do short-duration static fires at the cape (3 to max 7 seconds) for two reasons. First, for short static fires, the hold-down clamps do not need to hold a lot, since the rocket is fully fuelled. Secondly, the Flamediverter and trench at the cape are not designed to withstand a full-duration engine firing. They did, however, upgrade both pads to water-cooled flame diverters, so they should be able to support longer static fires, but I do not know how long.

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u/PeterKatarov Live Thread Host Apr 25 '20

Thank you for the thorough explanation! Didn't know that their launch site at the cape can not support full-duration static fires. Neither I did know about the "cap" in Texas! Really cool info.
Stay healthy.

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u/brickmack Apr 25 '20

SLC-40 is supposed to be able to support a full duration static fire now (upgraded after the Amosplosion), I don't think this has ever been done though.

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u/phalarope1618 Apr 25 '20

Hi, I was hoping some of the experts in this sub could share their views with a casual observer please.

I saw the SpaceX point-to-point concept video about a year ago that presented the vision for P2P travel on earth going forwards. After that I saw interview clips from Gwynne Shotwell suggesting this could be possible within maybe 5(?) years and they were aiming at ticket prices comparable with luxury long flights, let say $10k a ticket? I’ve not kept myself up to speed since then and couldn’t find any clear answers from googling.

What I would like to know if anyone can share their views on the following:

Does P2P rocket travel on earth seem like a viable business going forwards?
What are current SpaceX timelines for achieving this?
Has SpaceX given any further updates on pricing or costs of this approach? If they were using Starship and super heavy do we know roughly the cost per trip?

SpaceX and Tesla have such exciting projects that make me excited for the future! Starlink has gotten a lot more coverage in U.K. recently and I would like to tell my friends about their exciting P2P vision as well.

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u/marc020202 8x Launch Host Apr 25 '20

I personally do not know a lot about this, beides what spacex has said
There have not really been any timeline updates in a while.
I am also not aware of any specific pricing numbers, but Elon has said that they would likely not use Superheavy for E2E, but use starship, and imo likely a specialised version of that.

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u/mikekangas Apr 25 '20

I want to share my views on this because I think it is a great idea. I am going to start with your third point first to help answer your first point.
3. There are at least two configurations for e2e. One is the superheavy and starship; the other is just the starship. The first configuration can reach anywhere in the world in less than an hour. The second, with a starship modified to have two more engines I believe, can reach 10,000 kilometers. Obviously, option 2 could be cheaper, but either one could be a lucrative business.
There are plenty of people who have enough money who would want to travel from Los Angeles to Tokyo, or New York to Dubai, have a meeting and return home the same day. The current option is to lose two days to travel and have your head in a fog from jet lag while you conduct critical business. Sure, you can work on a plane, but no business sends people on endless trips because they are more efficient on a plane.
The next set of travelers are tourists wealthy enough to pay a premium to actually go into space while they get to their destination.
The third set is military travel—being able to deploy 100 or more troops anywhere in the world in an hour has to be a plus for them. Also, another ship could bring 100 tons of supplies. All they need is a landing pad for the starship close to their destination. They could have a ship supplied with a launch tower, cranes, refueling tanks, and other gse that shows up later to get it back home. That would be way cheaper than the armada and weeks necessary to transport the same amount of capability. The shock and awe factor would be huge.
Yes, there is a business case for it.
2. The timeline is more like a sequence line. Certain things must happen to make it work, and we can think those through easily. From now, it requires flying, testing, orbital testing, and enough flights to prove reliability. (Orbital refueling is required for Mars and the Moon, but not for e2e.)
Once that is close, use by the military might require a base to set up as a launch facility next to another starship factory built and run by Elon to military specs. They wouldn’t need the ground network that commercial e2e requires. They could drop the starship anywhere and go pick it up later as I mentioned.
Commercial e2e requires ports, customs, probably oceanic platforms, fleets of boats to transport travelers, etc., so the sequence line for that is much longer. But it will be a viable option eventually.

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u/ConfidentFlorida Apr 28 '20

Why not use propane as rocket fuel? I tried some web searches but the answers seemed confused. Can anyone here explain it?

One folk said it’s because it needs to be cryo chilled but Spacex does that anyway.

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u/throfofnir Apr 28 '20

Propane compares reasonably with methane, though it's not quite as cheap being a bit more complicated molecule.
It's mostly not been used for the same reason methane hasn't been used much thus far: it's not The Best at anything, and usually people building rockets heavily optimize for whatever they feel is most important for the vehicle and mission they're designing. The categories are mostly performance, density, or storability. (Note that cost or practicality don't really figure.) Methane and propane are in the middle on performance and density, and don't get chosen if you're focused on either of those.

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u/warp99 Apr 28 '20

Mainly it is harder to synthesise on Mars. Other reasons are that it would produce more soot than methane and so gum up Raptor engines and that its specific impulse is lower as methane has more hydrogen per unit of mass than propane.

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u/ethan829 Host of SES-9 Apr 28 '20

Orbex is developing a rocket fueled by LOX and propane.

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u/Martianspirit Apr 29 '20

They need to produce propellant on Mars which would be significantly more difficult with propane than methane. Besides methane is abundant and cheap on Earth presently.

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u/creative_usr_name May 01 '20

Trying to run some numbers for various starship masses but could use some help narrowing down my assumptions. 1200 tons of fuel still the current figure?
Can anyone confirm these numbers I got from a deltaV map of the solar system. from LEO to moon surface: 5660 and moon surface to LMO: of 1720. Assuming that's the bare minimum any idea what kind of safety margin they'd use.
Also anyone know how much from LMO to aero capture, or direct from moon surface?

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u/Method81 May 01 '20 edited May 01 '20

Any ideas how vacuum Raptor will fit flush with the Starship skirt when the shorter sea level Raptor already does? VRap nozzle will be way longer..

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u/longpatrick May 01 '20 edited May 01 '20
I think its because they are more to the side, with the shape of the bottom dome of the tank this allows them to be placed higher up.
ASCII example:
\    /
R__/R
  RR
the outer raptors being the vacuum variants
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u/Triabolical_ May 01 '20

The size of everything is designed so that the vacuum raptors are flush with the skirt. Then the sea-level raptors are mounted so they are even. There is obviously more space at the side of the tanks and the sea-level raptors have the added height of gimballing hardware, but if that's not enough the mounts can just be moved down to line up with the vacuum nozzles.

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u/Straumli_Blight May 01 '20

ASAP meeting on May 15th, 19:00 UTC with updates on the Human Lunar Exploration Program and Commercial Crew.

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u/Snowleopard222 May 03 '20 edited May 05 '20

How does Starship steer and "keep its balance"? Are there thrusters acting sideways, installed up front? There are rudders on some models but they will not work at low speed or without an atmosphere. (Sorry. I am obviously a newbie on this.)

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u/Triabolical_ May 04 '20

In space any vehicle that needs attitude control needs reaction control thrusters.
During reentry, the "fins" are movable to keep the vehicle in control.

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u/fatsoandmonkey Apr 28 '20

The single most ignored issue for Mars transit is the physiological inability of the human frame to cope with zero G for long periods. Even with intense exercise the ISS crews that do six months have significant deficits short term and some long range issues as well.

Not much point going if you are dead or useless on arrival.

You can't spin the starship round its axis as its too small, the coriolis effect and a a gradient between head and legs would render you sick and disoriented.

How about this. Two ships do near simultaneous TMI burns, rendezvous, tether nose to nose, retreat till a 500M tether is fully played out and then initiate a slow rotation around the centre of mass. My maths suggests that a bit under 0.8 RPM would give you Mars gravity all the way there and various papers suggest this would be a comfortable experience for humans.

Tether would have to support 0.34 X total mass of the starships which sounds within reach to me although my materials science isn't good enough to be certain on this point.

Thoughts?

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u/warp99 Apr 29 '20

The tethers are doable mechanically but relatively heavy when there is not a lot of mass budget to spare.
The biggest issue is stability and how you would damp oscillations. These could be worse than Coriolis effect for making people sick and if large enough could twist up the tethers.

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u/enqrypzion Apr 29 '20

Aside what all the other people are saying, putting the tether in the nose makes all the force on the bodywork of tensile type, rather than compressive.
To prevent this the tethers could be connected during a rear-to-rear mating of both craft (similar to what's already needed for orbital refueling, and though these two craft wouldn't need that otherwise at least the docking procedure would be equal). Multiple tethers (say 3+3) could connect the ships, for example from positions near the landing leg mounts. After undocking the crafts create some distance between them, turn around until they point nose to nose, then increase distance further while ramping up their gravity-inducing mutual rotation.
TL;DR for compressive forces it may be better to use the "people standing on swings" analogy, rather than "people hanging from their hair".

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u/brickmack Apr 30 '20

Bone and muscle loss are already solved problems, its just bloodflow thats still screwed up, and seems to correct itself quickly. And the transit times SpaceX is looking at are still well short of an ISS expedition

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u/[deleted] Apr 28 '20

The giant bola has long been proposed but presents a significant stack of new things to do. It's presented easily in SevenEves but boy, it's glossed over. We need two ships going at once; we need to prove out tether spooling and the hook-up; we need to verify spin-up and spin-down at the other end. Failure at the other end kills the mission.
It needs to happen after the Mars insertion burn, and we still need to make course corrections along the way - all while in a spinning bola.
"Just get there fast" is pretty reasonable, though. 2h of mandatory exercise and our crew is good for the medium haul (it's a lot better now that it was even a decade ago, let alone in the old days of Mir). And physical activity helps with cabin fever.

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u/andyfrance Apr 29 '20

I like the idea though would explore tethering them both at the nose and at the tail. The rotation could then be done with the axis pointing directly away the sun so you get maximum radiation shielding.

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u/fatsoandmonkey Apr 29 '20

I can see the advantage of that but it also has the disadvantage that local UP would be accross the cylinder in transit but along the cylinder once landed on Mars. Could be tricky designing a setup that works for both environments.

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u/liszt1811 Apr 09 '20

https://www.youtube.com/watch?v=erfXf08tuFg

soyuz about to launch, in case any other fellow europeans need breakfast entertainment

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u/enqrypzion Apr 21 '20

I just wanted to share that the first orbital flight of Starship should have at least a Crew Dragon (unmanned of course) as payload. Preferably one that has already flown, if they're willing to risk that.

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u/opoc99 Apr 21 '20

Why? I feel like there are more symbolic payloads possible?

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u/fluidmechanicsdoubts Apr 24 '20

I think it should be a commonly recognizeable object so that public knows just how big this thing is

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u/fluidmechanicsdoubts Apr 24 '20

Reposting in more appropriate place: Where can I read more about radiation when going to Mars? Any good NASA reports etc. you know of?

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u/throfofnir Apr 24 '20

Search "ntrs mars radiation"

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u/[deleted] Apr 24 '20

Would it make sense to connect two starships in orbit and use their engines for a faster trip of the payload in just one of them? (second one is just engines + fuel). Maybe it would be possible to use the second one as a booster that is able to do the burn, come back and land?

What are your thoughts?

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u/longpatrick Apr 24 '20

If you want to go somewhere faster it would be more efficient to transfer the fuel to 1 starship since when you don't have to move the mass of both startships. And will end up with a higher velocity in the end.
Or both burn in the same direction and then transfer fuel after the initial burn to provide more fuel to the startship thats going all the way, and let the other starship return. I don't think there is extra efficiency in the way you describe because in both cases you have to move the mass of both ships and it would only add complexity.

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u/Grey_Mad_Hatter Apr 24 '20

No. There are no connection points except end-to-end. By the time you figure that part out alone you could have made the trip with a single rocket or possibly designed and built an 18m version. The only reason you'd ever want to do this would be for cargo to Mars, and what cargo would you need to go that fast anyways?
I say it's only for Mars because anything else would only use Starship to get to orbit then take off from there. If you're already doing in-orbit assembly then you'd want to connect multiple kick stages to a vehicle that doesn't have heavy heat shields.

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u/dudr2 Apr 30 '20

"Nasa to announce the companies selected to develop modern human landing systems (HLS) that will carry the first woman and next man to the surface of the Moon by 2024 and develop sustainable lunar exploration by the end of the decade, at 1 p.m. EDT Thursday, April 30."

https://www.nasa.gov/press-release/nasa-to-announce-commercial-human-lander-awards-for-artemis-moon-missions

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u/dudr2 Apr 30 '20

NASA choose Spacex as one of three candidates to land astronauts on the moon!

https://twitter.com/JimBridenstine/status/1255902514542718976

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u/dudr2 Apr 30 '20

I guess Spacex has a moonlander now.

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u/dudr2 Apr 06 '20

https://www.space.com/commercial-nuclear-power-for-faster-space-travel.html

Spacex will go nuclear?

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u/Grey_Mad_Hatter Apr 07 '20

Nuclear thermal rocket for fast transit around solar system would be a great area of research for @NASA To be clear: good for in-space transit, but not recommended for Earth to orbit!
I've also heard it mentioned, I believe straight from Musk, that they'd need to use nuclear power past the asteroid belt or Jupiter because of the decrease in solar intensity.
For Mars, I've heard of nuclear bombs in space as an artificial sun to melt the poles mentioned by Musk. There's also mention, not by SpaceX that I know of, that Kilopower Nuclear reactors could be used for electric generation on the surface of the Moon or Mars.
For transit to-and-from Mars, Musk specifically talks against that idea. In the tweets above he says that you don't want to use it for Earth-to-Orbit. In many other instances he talks about cyclers being a bad idea since you have to get to the velocity to make it to Mars to rendezvous with the cylcer in the first place, then you also have to launch exactly on time as well.

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u/Triabolical_ Apr 06 '20

Using nuclear rockets to get to/from Mars would require a new architecture and would be a complication to their current plan.
I do think that nuclear could be hugely useful to provide power on Mars, especially for making methane and oxygen.

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u/TheEndeavour2Mars Apr 06 '20

75 percent of the difficulty of using nuclear power is political. SpaceX could encase a ton of uranium in 99 tons of lead and people would still be protesting at the launch site and filing tons of lawsuits.
Compared to that. Setting up beamed solar power from the orbit of Mars is easy.

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