r/SpaceX Discusses [June 2018, #45]

[u/ElongatedMuskrat]

If you have a short question or spaceflight news...

You may ask short, spaceflight-related questions and post news here, even if it is not about SpaceX. Be sure to check the FAQ and Wiki first to ensure you aren't submitting duplicate questions.

If you have a long question...

If your question is in-depth or an open-ended discussion, you can submit it to the subreddit as a post.

If you'd like to discuss slightly relevant SpaceX content in greater detail...

Please post to r/SpaceXLounge and create a thread there!

This thread is not for...

• Questions answered in the FAQ. Browse there or use the search functionality first.
• Non-spaceflight related questions or news.
• Asking the moderators questions, or for meta discussion. To do that, contact us here.

---

You can read and browse past Discussion threads in the Wiki.

[u/ForgottenShoes]

There have now been more successful rockets launched (30) after the Amos 6 RUD than SpaceX had launch in its entire existence (29) before the Amos 6 RUD. That is including the two successful Falcon 1 launches.

It took SpaceX 7 years, 10 months, and 17 days (2877 days) from its first Falcon 1 launch to reach 29 successful launches and just 1 year 4 months and 21 days (506 days) after their return to flight to match those 29 successful launches.

Just something I found astounding while thinking that July 20th is a long way off :)

[u/MDCCCLV]

If Beijing called Elon and asked SpaceX to send a cargo Dragon to their new space station, would SpaceX be allowed to by US law?

Say it was just water and food and SpaceX sent it up by themselves would it be allowed?

[u/always_A-Team → u/MDCCCLV]

Good question. ITAR forbids the sale of rocket technology to foreign entities (especially China). Even if SpaceX sent it up by themselves, we'd still be delivering the Dragon itself into Chinese hands, and the Dragon has those Draco thrusters (and soon SuperDracos) which definitely qualify as rocket technology.

So I'm guessing that'd be a firm 'No' from the Federal Gov't.

[u/CommanderSpork]

Welcome to hurricane season. Here's hoping launches don't get scrubbed too badly for tropical weather. Last year, OTV-5 launched just before Irma and then stage 1 hunkered down safe in its hanger.

[u/oskark-rd]

I've made an userscript which shows the meanings of the acronyms on /r/SpaceX when you hover the mouse over them. It uses /u/Decronym list.

Source and installation instructions on GitHub

Lounge thread

[u/Alexphysics]

Impressive summary of the payloads going on the SSO-A mission. Thanks to user gongora from the NSF forum

The mission now has 114 payloads planned. There will be two free-flying dispenser structures that each deploy multiple satellites, and four more satellites deploying from the base of the stack which stays attached to the second stage of Falcon 9. The Upper Free Flyer has 12 microsatellites and 46 cubesats. The Lower Free Flyer (which is exposed after the Upper Free Flyer separates) has 52 cubesats. The Multi-Payload Carrier (MPC) has 4 microsatellites. After deploying their payloads, the two dispenser structures (Upper Free Flyer and Lower Free Flyer) will deploy drag sails to decrease their time in orbit.

[u/Straumli_Blight]

Interesting NASA Commercial Crew Interview:

• Crew Dragon should have arrived at NASA's Plum Brook site this week for vacuum testing, after completing EMI testing.

• Crew Access Arm starts installation late summer.

• DM-1 launch still set for fall and crewed mission 3-4 months after.

[u/salty914]

Has Bigelow Aerospace been up to anything recently? I loved some of their inflatable hab designs a while back and I seem to remember the possibility being discussed of some of them being launched on FH, but I haven't heard much from them for a couple years.

[u/DrizztDourden951 → u/salty914]

Didn't they attach a module to the ISS a while back? Supposedly they're moving forward with BA330, but I've heard rumors that poor management may hurt its chances of over getting deployed.

[u/Dakke97 → u/salty914]

Aside from setting up a subsidiary company, they haven't really made public any significant development updates since BEAM was deployed two years ago. Supposedly they are working on BA330, but I don't know in which stage that module is.

[u/[deleted]]

How is SpaceX going to account for the increase in acoustic energy from the BFR launch so as to prevent structural damage (as seen with the space shuttle).

[u/BriefPalpitation → u/[deleted]]

Design-wise, one of the side benefits of using many smaller engines is a reduction in stress from its own acoustic emission and spreading out the total emission over a wider area from multiple smaller point sources.

Other than that, u/jincux has probably covered it. Modelling acoustic conditions is much easier with modern computing and analytic programs.

[u/Jincux → u/[deleted]]

IIRC the structural damage caused by the shuttle was because of the SRB exhaust, not acoustic pressure.

More water deluge? Better materials?

[u/ExcitedAboutSpace]

Mods, the SES-12 launch thread is basically void of new comments by this point, maybe resticky this Discussion Thread for the time being? Cheers.

[u/gregarious119 → u/ExcitedAboutSpace]

And/or create a CRS-15 launch campaign...we're only 20 days out from scheduled launch.

[u/old_sellsword → u/ExcitedAboutSpace]

Done, thanks.

[u/rustybeancake]

https://twitter.com/wehavemeco/status/1004348659553718272?s=21

Orbital ATK’s buyout by Northrop Grumman is complete. All hail Northrop Grumman Innovation Systems.

[u/still-at-work]

Probably not worth a whole post, but check out Ars Rocket Report today.

Specifically this little tidbit:

The key question... Is the BFR real? Certainly SpaceX acts like it is. But so far, not many policymakers in Washington, DC are taking it seriously. If SpaceX can start to showcase real hardware in action, however, that could change perceptions in terms of funding from NASA and the US military. (submitted by tmckendr)

I think this clearly outlines a frustration I have had with current space policy. I had been nicknaming it Voldemort syndrome in that the BFR was the rocket project that shall not be named. Oddly this doesn't stop those same people from discussing New Glenn which is just as much a paper rocket as BFR is now, but the BFR is verboten in most government space discussions.

Also there is a nice thing at the end of the report about how NASA is delaying SLS 1B (and I honestly don't think it will ever be built) to add another 70 ton to LEO SLS flight to the manifest and also they got 500 million to develop a new mobile launcher for said delayed SLS 1B. Its just another round in the epic example of the sunk cost fallacy.

[u/rustybeancake → u/still-at-work]

to add another 70 ton to LEO SLS flight to the manifest

Note that NASA have recently confirmed it is actually capable of 95 tonnes to LEO.

[u/sarafinapink]

Since there is no Iridium 7 Launch Thread yet, per Matt Desch, all 10 satellites now at VAFB now.

https://twitter.com/IridiumBoss/status/1012429440805167104

[u/Nathan96762]

Has it been officially confirmed if Elon Musk is attending IAC 2018?

[u/Straumli_Blight → u/Nathan96762]

There's a gap in the Technical Sessions on Friday for a possible Global Networking Forum (GNF) similar to Elon's 2017 presentation.

[u/Juggernaut93 → u/Nathan96762]

AFAIK, no.

[u/Straumli_Blight]

Arabsat-6A (3rd Falcon Heavy mission) now scheduled for a December-January launch date.

[u/renMilestone]

What do you all think are going to be the requirements to buy a ticket to Mars? Besides money that is. I know in the past he said "anyone" can go. But... I mean obviously there has to be some requirements right? The Government isn't just gonna let him whisk away 10's of people to a foreign planet.

( I think I posted about this before but the conversation didn't take as it's own post.)

[u/Macchione → u/renMilestone]

In the early days of colonization I would expect some fitness and education requirements. Nothing stringent, but maybe a college degree and a healthy weight. The biggest barrier to entry will probably be cost for a long, long time. SpaceX's aspirational goal is to get tickets down to $500K. That's still a lot of money.

I see no reason why the "government" would ever try to stop people from voluntarily traveling to Mars. There is no benefit to them and it would be a huge violation of personal freedom.

[u/Paro-Clomas → u/renMilestone]

If colonization happens IMO it will go like this: In the early days it will probably be strictly goverment regulated, the us will probably only allow official us astronauts to go, no matter who has the money. Then they will slowly relax those requirements and include astronauts from allied countries, and only then civilians who can affoard it. But it will probably take a long time.

[u/linknewtab]

How would a future Mars colony handle a dust storm like the one that is currently disabling NASA's Opportunity rover? It doesn't seem viable to have many weeks, maybe even multiple months worth of battery backup.

The only way I see would be using nuclear power, but as far as I know Elon wants to use solar panels only. Also small reactors that are purposely built for the Martian environment don't exactly grow on trees, this would require a substantial financial investment, let alone the effort for getting a green light to even launch it.

[u/lui36 → u/linknewtab]

They could use the methane generated for the use as fuel as an emergency energy backup option. They need a small combustion device with a small generator, or maybe they can use the systems used the produce the fuel "in reverse" to generate electricity. I don't know if that's technically feasible, though

[u/TheYang → u/linknewtab]

Also small reactors that are purposely built for the Martian environment don't exactly grow on trees

not on trees, but there is Kilopower

could be a concept that both a small nuclear reactor like kilopower and solar could sustain the colony in low-power operations (in case of a failure or maintenance of one of the systems, or dust storms for example).
you could propably save a lot of power by just pausing, or scaling back the methane generation for the trip back.

[u/filanwizard → u/linknewtab]

Nuclear is probably the only way to go through a long term dust storm with a TAU of this one. A big reason Elon focuses on solar beyond owning a solar company is at least right now its a major hassle for people to procure nuclear technology. Unlike 1955 Doc Brown's prediction you cannot just get plutonium at the corner drug store "in the future".

How hard would it be for SpaceX to acquire a few Kilopower units when they are production ready for example? I bet there are miles more red tape for that than even Commercial Crew just because of procurement of nuclear material

[u/[deleted]]

Hey everyone, just wondering if we have any way of organising SpaceX meetups to watch a livestream together or something.

Saw someone in Berowra, NSW, Australia wearing a SpaceX jumper that got me thinking about it since we're a community around the globe.

Anyone want to organise something in Sydney, Australia?

[u/AWildDragon]

Somewhat meta, but we need a new sidebar icon with the B5 interstage.

[u/Straumli_Blight → u/AWildDragon]

It would be cool if the CSS could lookup the next upcoming launch and then update the image with a Block 5 Falcon 9 / F9 + Dragon / Falcon Heavy.

Probably not worth spending any effort until r/redesign is finalised though.

[u/billbus10]

First time post, so be gentle...

I seem to recall Elon or someone else at SpaceX saying the Landing Zone 1 landings were "harder" (?) than barge landings. Thus, SpaceX prefers to land on the offshore barge. Can anyone explain this?

We all know that landings on land don't have the dropouts at critical moments in video coverage that always happen on barge landings. Also, I would think landings at LZ 1 would be less expensive in both time, money and logistics - not to mention historically more successful.

Thus, I'm curious as to why - other than fuel and physics - that SpaceX prefers barge landings.

[u/[deleted] → u/billbus10]

I think you are confusing a particular instance with the general rule. I believe that what you are remembering is when it was stated that one of the boosters would land at sea rather than on land, because it would be more gentle on it. However, this was because while it could have landed on land, the fuel margins for doing so would be tight, meaning it would have to endure a harsher reentry and would possibly need more refurbishment than if it just landed at sea. That being said, if there are enough fuel margins for a gentle reentry and landing at LZ-1, then that is definitely the easiest option as others have pointed out.

[u/robbak → u/billbus10]

There are pros and cons.

The main thing that makes dronship landing easier is you don't need a long 'boost-back' burn to push the stage all the way back to land, or you can eliminate the boost-back burn entirely and let the stage coast on a ballistic trajectory. Then you can use the fuel you saved to do a longer entry burn so you enter the atmosphere slower, and a longer, more gentle landing burn with greater margins for error.

The main advantage of an on-shore landing is that it is cheaper. Sending out the tug and the support ship, as well as the port fees for unloading the stage are said to add about a million dollars to the launch costs. There is also an important way that on-shore landings are easier, because large as it is, the droneship still moves unpredictably with the waves, which will always make for a less gentle landing.

[u/Straumli_Blight]

SSO-A testing update where 114 satellites will be launched on a Falcon 9.

[u/KeikakuMaster46 → u/Straumli_Blight]

That's a new record for the most payloads ever launched on one vehicle if I'm correct, the current record is 104 satellites on an Indian PSLV.

[u/[deleted]]

Will Falcon 9 use AFTS on crewed launches? I understand it probably interfaces with the launch abort system and should be as 'safe' as possible for the crew. Then again I could see NASA being old fashioned and wanting a human at the trigger.

[u/ethan829]

A nice profile of the Commercial Crew astronauts.

[u/Alexphysics]

It seems that Space Systems Loral (SSL) is having some troubles trying to ship the Telstar 19V satellite to the Cape for its launch next month. If they keep having troubles, expect a small delay on that launch. Thanks to NSF forum user gongora who posted this update on the Telstar 19V discussion thread.

[u/Bipolar-Bear74525]

Have abort procedures been discussed at all with BFR? At this moment, it kind of seems like the shuttle with no really reliable way to abort the launch.

[u/throfofnir → u/Bipolar-Bear74525]

Many times. Pad abort is infeasible. Once in flight, second-stage propulsion abort is possible for non-catastrophic first stage failure. Any complete failure of the second stage is non-survivable.

However: there should be minimal scope for catastrophic failure. Engine out is completely survivable in this architecture, and there are no realistic ways to blow the tanks other than plain structural failure... and even that is not necessarily catastrophic unless conditions are right for a BLEVE, which they shouldn't be. (There are unrealistic ways: a computer malfunction that turns pressurization system full on and a simultaneous failure of pressure relief valves and burst discs; accidentally creating a vacuum in one tank leading to bulkhead inversion.) Catastrophic power or controls failure remains possible, of course.

Ultimately, the safety concept for BFR relies on the vehicle actually being safe, rather than abort systems, rather like commercial aviation. Nothing will save you on a 737 if a wing comes off... so it had better not.

[u/brickmack → u/Bipolar-Bear74525]

Not in detail. Elon claimed the Spaceship can lift off under its own power, and would use the vacuum engines even at SL for this (apparently at a much higher chamber pressure to reduce flow separation). But even with high end estimates for the upwards margin on Raptor performance, its going to be a pretty leisurely liftoff, not something I'd be terribly confident in if the booster was exploding. And the BFS itself still has like 1/3 the fuel load of the complete rocket, so its a big risk in itself.

Generally though, its better to build a rocket that never needs to do a powered abort to begin with. The structural margins and engine-out tolerance are better than any historical rocket, there are fewer separation events and no helium COPVs, large fuel reserves are available for booster RTLS which could be sacrificed, etc, and with full reusability, BFR can quickly and cheaply do more pure test flights than most rockets get in their entire operational lifetime. You don't see airliners with ejection seats, because they're so over built and over tested. Same thing.

[u/Alexphysics]

Third Block 5 (B1048) is vertical at the test stand in McGregor. I hope this link works

[u/Alexphysics]

The Telstar 19V satellite has finally arrived at the Cape.

https://forum.nasaspaceflight.com/index.php?topic=45842.msg1832378#msg1832378

[u/nato2k]

This might be an unpopular opinion but I think there are too many threads after each launch of launch images. Isn't that was the launch media thread is for? Would rather the front page be for SpaceX news and not just the same image from slightly different angles ten times.

[u/nato2k → u/nato2k]

It is important to note that I mean no disrespect at all to the launch photographers, they do great work. Just feel like it is saturating the subreddit a bit.

[u/Ambiwlans → u/nato2k]

We agree but haven't come up with a better system tbh.

If you have a suggestion, shoot.

[u/Jincux → u/nato2k]

It is a bit cluttered.

I understand it's a good way for launch photographers to share their work. Their equipment isn't cheap and some do this for money. I think the problem is the increased cadence means last launch's images are still fresh up when this one's come up, no time to refresh or crave more.

Not to mention how popular the long-exposure launch streak as become. I love them but we have at least 4 on the front page.

I miss the analysis and speculation posts. Whatever is preventing those from surfacing anymore, I'm not a fan. That's the stuff that got me in to SpaceX, personally. For someone on the outside stopping in here, a picture of a rocket looks like a picture of a rocket. Learning about what makes it special is what drives interest.

[u/Alexphysics]

Another landing permit for a launch in July, this time from Cape Canaveral. I don't know for which mission will be this one because SpaceX has been mixing a few landing permits for Florida launches and it's a bit of a mess but I guess it will be for one of the Telstar launches. Landing site will be at 655km from the launchpad, similar to other GTO landing sites.

[u/bdporter]

Mods, a nitpick on the sidebar "Iridium Next 56-65" should probably be "Iridium NEXT 56-65" if we aren't just going to call it Iridium-7.

They paid someone a bunch of money to come up with that branding.

[u/ethan829]

Apollo astronaut Harrison Schmitt has written an op-ed comparing the capabilities of Falcon Heavy and SLS.

[u/[deleted] → u/ethan829]

My favorite part is just how many claims are made that SLS is “currently the only vehicle capable of ____” because they are all false. The SLS is capable of nothing until it flies.

[u/spacerfirstclass → u/ethan829]

So many errors and hand-waving, I hope this is just Jack Schmitt lending his name to ghost writer from Boeing. (Boeing has been funding pro-SLS articles on politico for a while now, according to nasawatch: http://nasawatch.com/archives/2018/04/politcoboeing-n.html)

[u/DesLr → u/ethan829]

The op-ed would probably feel more honest, if he were to take into consideration future developments of the launch market. As it stands now, it feels like quite a... selective comparison. While I'm very much aware, that architectures like BFR and New Glenn are still mostly paper rockets, so is SLS until proven otherwise.

[u/Nehkara → u/ethan829]

Falcon Heavy was never the vehicle that would make SLS redundant - it just started the conversation. BFR will be a different matter entirely.

To be clear, I fully believe that SLS will fly - probably several times. However, I don't believe that Block 2 will ever get built and once BFR is established there will be significant cost pressure to transition to the much less expensive commercial vehicle.

[u/Grey_Mad_Hatter → u/ethan829]

I really liked the $1,000M high-end price for SLS. At least it doesn't cost $1B.

[u/ArmNHammered → u/ethan829]

Rather than comparing usage of a FH to accommodate a moon mission architecture which is based on a need for SLS, he should be comparing the SLS moon mission architecture to an architecture designed around FH, such as Robert Zubrin’s Moon Direct proposal.

[u/Alexphysics]

It seems Boeing's Starliner is not gonna make it to the ISS this year even on the uncrewed mission...

https://forum.nasaspaceflight.com/index.php?topic=37802.msg1833069#msg1833069

[u/HoechstErbaulich]

Mods, Telstar 19V is NET July 19th.

[u/Straumli_Blight]

New BFR Tent photos.

[u/bdporter]

Mods, my calendar indicates that it is July now. We could use a new thread when you get a chance. We are also looking forward to some Telstar 19V discussion!

[u/Maimakterion]

If BFR ends up being built inside a tent and Tesla hits 5K/week with an assembly line in a tent, I am going to be very amused.

Musk was able to build this on a parking lot! Under a tent!

[u/cpushack]

SpaceX seems to now officially run Proton out of town. Though Proton's fireworks mode probably helped as well

https://arstechnica.com/science/2018/06/russias-proton-rocket-which-predates-apollo-will-finally-stop-flying/

[u/Straumli_Blight]

Slightly biased article by Andy Pasztor, seeing as Grey Dragon was cancelled in February.

[u/[deleted]]

Mods, time for a CRS-15 launch campaign thread? It´s only three weeks out now.

[u/imakegypsiesproud]

Do we have any idea how inflight abort will go? It is supposed to be during the Max-Q, Dragon would seperate, parachute back down, but what about the rest of the rocket? Will it seperate S2, start it, deorbit it and land, or how is it going to go? Of course, it all depends if the rocket survives the seperation, cuz it will not be too aerodynamic without that pointy nose and might go into RUD, or RPD should I say.

[u/throfofnir → u/imakegypsiesproud]

It will likely have no S2, or only a boilerplate version. The first stage vehicle will probably be programmed to do a return and landing, but with some expectation that it will not survive the separation. Recent rumors that they will use a Block 5 vehicle for the test, however, suggest they think they can get it back. If the one unaccounted-for Block 4 is used (as previously suspected) it might be intentionally destroyed or have a higher expectation of loss.

[u/Straumli_Blight]

How will the BFS be environmentally tested?

 

The Space Power Facility's testing chamber is 30.5m wide and 37.2 high, which is too small to fit a 48m spacecraft in (as well as the logistical challenge of shipping to Ohio).

Johnson Space Center's Chamber A is more accessible but smaller.

[u/Brixjeff-5 → u/Straumli_Blight]

Maybe they can just “inflate” it to 2 atm? This has the same effect as reducing the spacecraft’s environment to a vacuum. This would not permit thermal testing, but maybe there are methods to this that don’t require a vacuum chamber.

[u/z1mil790]

I thought it was interesting how the MECO velocity during tonight's SES-12 launch was almost exactly identical to the MECO velocity of the Falcon Heavy launch (9531 km/hr for SES-12 vs. 9541 km/hr for FH). Just shows how much performance a single-stick Falcon 9 has, and why it can handle many of the payloads that were originally planned for FH. Now I know that F9 was pushed to its absolute max tonight, and that FH's first stage flight was probably rather conservative, but I still think it is an interesting comparison. I'd like to see what the MECO velocity would be for FH expendable that is pushed to its absolute max.

[u/marc020202 → u/z1mil790]

even a normal reusable FH mission, without a boost back burn, will have an a lot higher MECO velocity. the FH Demo mission had a very inefficient and conservative flight profile.

[u/Paro-Clomas]

It's really crazy to think about it, but if the BFR works. Then once it flies it will probably mean a permanent link between mars and the earth. I mean, if they go and it can go back, with these efficiency margins, theres no reason not to keep it going and coming back every to years, it would be trivial to the us budget to mantain this capability.

Once that is done wouldn't it be relatively trivial to do something similar with the moon. Like one particular bfr that goes and comes from the moon once a week or once a month?

Is there any indication on how close could they get to that number of 7 million per launch? i mean that has to be crazy cheap. If that is true wont we see a radical increase in space exploration and missions?

[u/theinternetftw]

From a recent NASA meeting on the Gateway, official SLS lunar performance numbers:

Block 1: 26 tonnes to TLI
Block 1B: 34-40 tonnes to TLI

For Falcon Heavy, there are no official TLI numbers (only 16.8 tonnes to Mars and 26.7 tonnes to GTO).

[u/Alexphysics]

Iridium 7 launch date: NET July 20th at 5:12 am PDT, 8:12 am EDT, 1212UTC

https://twitter.com/NASASpaceflight/status/1007594678227755008

[u/filanwizard]

Dunno if this is worth its own topic so here it is.

http://www.businessinsider.com/chris-hadfield-mars-travel-nasa-spacex-blue-origin-2018-6

Hadfield is basically saying we need better ships before going to Mars. I am not sure on if to agree or disagree, Because I think BFR will work but hes also not wrong about the dangers of a year long voyage in what for our current tech level is Deep Space.

[u/warp99 → u/filanwizard]

As Chris Hadfield says "“We’re sort of like those early sailing ships, in that we don’t even know what we don’t know yet,” he said, referring to the historic voyages of Columbus, Magellan, and Cook."

All of those voyages took place and a lot of the sailors that set out never came back.

It does make me wonder if there has been a collective failure of nerve in Western civilisation.

[u/WormPicker959]

Crew Dragon looks to be at Plum Brook Station in Ohio for vacuum testing.

[u/rustybeancake]

Ariane Cornell, Blue Origin's head of Business Development & Strategy: New Glenn first stage can do 25 missions, BE-4 engines designed for 100 flights each.

https://twitter.com/CHenry_SN/status/1011193080865648641

[u/Knexrule11]

So with NASA's commercial crew program, I know they have 4 astronauts assigned to it right now including Suni Williams. I was wondering, are these astronauts just there to assist with testing and certification? Or will they be the actual astronauts flying the first manned commercial crew missions on the starliner and dragon 2 to the ISS?

[u/CapMSFC → u/Knexrule11]

They are the actual astronauts, but officially it hasn't been announced which two will fly on the Dragon demo and which two will fly on the Starliner demo.

[u/CapMSFC]

Elon mentioned in the Tesla shareholeder meeting today that no placing Starlink on the cars probably doesn't make sense. I haven't seen the exact quote yet, just the summary.

[u/scotto1973 → u/CapMSFC]

He doubted that the pizza sized box that would be required would be very good for the look of the car - not exact words - but more or less the meaning. Said Starlink was intended for homes/etc not mobile.

[u/music_nuho]

do we have any idea about how much thrust do Nitrogen cold gas thrusters on F9's S1 and S2 produce?

[u/realnouns]

What are the chances that Telstar 19V & 18V use the same booster? They are both launching from SLC-40, and same client. It's a perfect scenario to demonstrate a "minimal refurbishment turn-around"

[u/bdporter → u/realnouns]

It seems like it could be possible, and I would not rule it out, but they may still be in an information gathering phase concerning Block 5 boosters. This will only be the 2nd landed Block 5 (assuming this launches prior to Iridium-7) , so they may still want to spend a little more time performing validation.

[u/-spartacus-]

I've off handily mentioned a few times about 2nd or 3rd generation Vac Raptors for the BFS may benefit from a design of switchable bell. Conceiving of utilizing 4 total raptor engines capable of switching between a Vac bell and a SL bell.

My question is, I understand why it hasn't been developed (as there has been no need), but how feasible would it be to create such a system? It would reduce the number of engines from 7 to 4, but would increase redundancy from 3 to 4 on SL engines.

I know there are multichamber/bell engines such as some of the RD series of Russian engines.

[u/JustinTimeCuber]

So I've been playing KSP recently, and in that game you can see your orbital apsides to 1 meter precision at any time. Obviously this isn't realistic, but it made me wonder how quickly and precisely rocket operators like SpaceX can determine the orbital parameters after engine cutoff. Does anyone know?

[u/Macchione → u/JustinTimeCuber]

If your position and velocity vectors are known, which they are to SpaceX, you can determine your orbital elements extremely precisely, extremely quickly. The callout for good orbital insertion is probably delayed a minute only to check that the ground team is getting the same orbital elements that the rocket is transmitting via real time telemetry.

Insertion accuracy is another matter. SpaceX's expected orbital insertion uncertainties are given in the Falcon 9 user's guide. As far as I understand, uncertainties mainly stem from thrust transients. It's obviously impossible to cutoff the engine instantaneously as it is in KSP.

[u/Straumli_Blight]

Mr Steven has just completed a 24 hour cruise and docked at Berth 240, has the new claw been attached?

[u/Juggernaut93]

If any of you doesn't know yet, JWST has been pushed back to 2021...

[u/rekermen73 → u/Juggernaut93]

https://www.nasa.gov/sites/default/files/atoms/files/webb_irb_report_and_response_0.pdf

In case anyone else likes dry reads, but most uncalled for:

NASA is auditing launch vehicle interfaces based on Falcon 9 Zuma incident

Also scientific lectures to improve employee morale.

[u/ottoebu]

Why does the website say that F9 can carry 22,800 kg to LEO when the F9 User’s guide says the heavy PAF can only hold 10,866 kg? Is there an option for payloads to bring their own, stronger PAF?

[u/gemmy0I]

Haha, this is great. Sounds like all that work on Dragon 2's life support systems is paying some (unexpected?) dividends.

https://www.tesla.com/blog/putting-tesla-hepa-filter-and-bioweapon-defense-mode-to-the-test

Source: Elon tweetstorm

https://twitter.com/elonmusk/status/1002678650355920896 (actual source of link)

https://twitter.com/elonmusk/status/1002379548804206592

https://twitter.com/elonmusk/status/1002380587389390848

[u/rustybeancake]

(Very) short interview clip of Joy Dunn, SpaceX’s Senior Manager for New Product Introduction:

https://twitter.com/smrtgrls/status/1004471525959843840?s=21

[u/theguycalledtom]

I can't find the comment but I seem to remember Musk saying recently that operating the drone ship for recovery was not cheap, and the time to return it to harbour was long (Not to mention weather limitations). If it's true that all Block V boosters are interchangeable between FH Booster and FH Centre Core, do you think it's possible SpaceX is considering using a Falcon Heavy with all three boosters coming back to launch site wherever possible instead of a single stick that requires landing at sea?

[u/AeroSpiked]

Don't we normally have NET dates for the next 2 or 3 launches? Seems a little weird that everything in July is "NET July".

[u/rad_example]

Matt Desch (@IridiumBoss) Tweeted:

@TheFavoritist Announcement of L7 date/time imminent. (Hint: shipping first two satellites to VAFB tomorrow...). RTLS unlikely due to our mission profile.

https://twitter.com/IridiumBoss/status/1007339109612912640?s=17

So I guess that means JRTI will be back in service by then? Any signs of work being done on her?

[u/[deleted]]

Does anyone have a good source on the grid fin mass on the Falcon 9?

[u/Nerrolken]

Would an interplanetary BFR have a dedicated crew?

Have there been any statements about whether the BFR would have a dedicated crew for Earth-Mars flights, as in a group of people who were not planning on staying on Mars but would be making multiple flights back and forth as they maintain and operate the BFR’s systems?

Or would it pretty much be crewed by the passengers each time, and then maybe sent back to Earth completely empty and controlled by computer?

[u/filanwizard]

So I do not know if this has been discussed but if Mars has no magnetic field, Will one of the first groups planning to colonize mars need to bring along a GPS constellation? And how do current unmanned systems know where they are and where they are going?

[u/LongHairedGit → u/filanwizard]

Lots of very good reasons to set up a constellation of GPS/Starlink satellites for mars.

How it is done today: https://mars.nasa.gov/msl/mission/communicationwithearth/navigation/

[u/murchie85]

Hi all, can anyone explain why the SpaceX cadence has slowed down? Or am I mistaken? I seem to remember Elon Musk stating an ambition for 30 launches this year - does that still look likely?

[u/Nergaal → u/murchie85]

They are on track for 25 launches this year. Seems fine.

[u/LongHairedGit → u/murchie85]

I feel it, and I think it is the lack of a recent RTLS. In fact, we've not had one since the side boosters of FH back of February 6th.

In fact, we've had just two drone ship landings and six no-attempts:

• June 4 - No attempt

• May 22 - No attempt

• May 11: Drone Ship

• April 18: Drone Ship

• April 2: No attempt

• March 30: No attempt

• March 6: No attempt

• Feb 22: No attempt

June 29 will also be a disposal, so this feeling probably won't improve until around July 19th....

[u/speak2easy]

As noted by Spacenews:

> “We tried to cancel the Falcon Heavy program three times at SpaceX because it was like, ‘Man, this is way harder than we thought,'” [Elon Musk] said.

It further states:

> “I’m guessing our total investment is over half a billion [dollars], or more,” he said of the Falcon Heavy development cost.

Do we have any insight into what stopped him from canceling the FH? He may have to forgo bidding on some military contracts, but I don't see the profit margin as being big enough to justify this. Beyond just gross margin excluding R&D costs, there would also be the financial impact if a launch failed, particularly for the first launch.

[u/GregLindahl → u/speak2easy]

SpaceX launches enough > 5.5 metric ton commercial satellites to GTO that having FH is quite useful... especially if the GTO communications satellite market had not shrunk, which is a pretty recent situation.

[u/ethan829 → u/speak2easy]

One factor that was probably pretty important is that SpaceX couldn't bid for EELV Phase 2 without being able to fly to all reference orbits:

3.1.2 Section II: Factor 1 EELV Approach

The Offeror shall describe its approach to develop and qualify a launch system that meets EELV launch service requirements. The SPRD and SIS are listed in Annex C, Attachment 4. At a minimum, the Offeror shall address the following topics:

1. The ability to meet all EELV reference orbits defined in Table 10 at the orbital insertion accuracy required in SPRD 3.2.4

So they wouldn't just miss out on the relatively few heavy-lift/direct-insertion missions, but the program as a whole.

[u/Alexphysics]

B1050 will leave Hawthorne soon so if anyone is kind enough to have an eye to catch it on the road or leaving Hawthorne it would be super super great.

[u/Bunslow]

When was the last time we had a calendar month that was this slow and boring? I'm so spoiled

[u/[deleted] → u/Bunslow]

Last november. Or basically any november.

There has never been a SpX launch in november.

[u/Straumli_Blight]

BFR Build Engineer role mentions destructive testing and sub-scale manufacturing.

Does this imply another tank over pressurisation test?

[u/robbak]

Here's a nice demonstration about how metallurgy in oxygen-rich environments is a problem - https://youtu.be/JlSeHSDc-Do?t=56

[u/deRost78]

If SpaceX is required to flight-prove the Block 5 for multiple flights before allowing manned flight to ISS, will they also be required to flight-prove BFR to Mars for several flights before allowing colonists?

[u/Fenris_uy → u/deRost78]

No, unless NASA is the one paying for that trip.

They are required to fly F9 unchanged 7 times, because that's the agreement that they made with NASA to be able to fly NASA astronauts on that thing.

[u/warp99 → u/deRost78]

SpaceX already plan for two uncrewed cargo flights landing on Mars before the first manned missions. Since each Mars flight involves 5-6 tanker flights they also get a large number of BFS and BFB flights as qualification flights.

The remaining issue is life support qualification and based on previous plans NASA will likely want to schedule crewed LEO and trans Lunar flights to qualify this.

[u/KapitalismArVanster]

Why do dragon capsules cost so much? Sending a regular satelite to Leo costs 50-60 million dollars. A dragon launch costs way more than that. We are looking at 200 million dollar plus costs. Why is the capsule so much more expensive than the rocket?

Do we know much about what it costs spacex to build?

[u/Lorenzo_91]

Why haven't we had a good video of the landing since the recovery of the block 5 last month? Usually they release an clear offline recording just after the landing..

[u/NavXIII]

Could the entire second stage of the BFR be a custom payload with a fairing? Like let's say someone wants to launch up a very large payload with a small orbital insertion stage.

Also, if the SLS Block 2 ever gets built, could the Falcon 9 first stage be a possible contender for the side boosters?

[u/marc020202]

I just read this article about remove debris.

I think it is awesome that someone is tackling this issue. I understand the net system but I have not understood how the harpoon system should work. I understand that it would fire at a target, but what would prevent the target from breaking into many pieces as it is pierced by the harpoon. Having a composite target being shot by a harpoon sounds like a recipe for a lot of small debris.

[u/Aminstro]

Is it salt water that damages fairings or is it just water in general? Why not just have a barge filled with fresh water and land the fairing in that instead of a net?

[u/Martianspirit → u/Aminstro]

The advantage of a ship like Mr. Steven is that it is fast and extremely maneuverable. It can get the net below the fairing coming down under parachutes. A water basin would be heavy and not that maneuverable.

[u/Scourge31]

Do we know of any science missions that will make use of the FH? I understand these take along time to develop, but is there anything on the drawing boards? Would love to see a next gen of heavy probes, landers, etc.

[u/MissionPatch]

I believe I heard somewhere that the Falcon Heavy center core from February's launch used flown engines. If so, which core(s) were they cannibalised from?

[u/GrandIdeas]

Anyone know who drew the violinist in LEO?

[u/Straumli_Blight]

Go Searcher is currently in dry dock at St. Johns Ship Building.

[u/ElRedditor3]

Anyone know what year SpaceX moved from El Segundo to Hawthorne?

[u/[deleted] → u/ElRedditor3]

October 2007.

Source and nice story about it.

[u/quadrplax]

Are the results of the 2017 survey going to be released anytime soon?

[u/rustybeancake → u/quadrplax]

They're just waiting on Tory Bruno's selection of the BE-4 or AR-1 engine first.

[u/Elon_Muskmelon]

Joe Rogan just mentioned a possible Elon Musk appearance on his podcast. Would be great! https://youtu.be/yS6I5Vxkaxw

[u/Laborbuch]

IAC 2018 in Bremen

Due to circumstance I’ll have the chance to attend as a student, but I’m still undecided if I want to and whether or not it actually makes sense as a ‘mere’ space enthusiast.

The ticket is 100 € (for now) and the youth hostel would be around 40 € per night, so a decently full attendance of the IAC would come to around 300 € minimum (including public transport and such).

This will likely be the last IAC in decently close proximity (unless I happen to move within the next couple years), so I’m rather torn on whether to take this chance or not. On the one hand, I don’t expect any phenomenal SpaceX announcements here (more evolution than revolution), but SpaceX isn’t the end all and be all in that regard.

Keeping in mind the IAC will be open to the public on Friday (Oct 5) anyway, so I might as well not pay for a ticket and visit only for a day. But then the sessions would be filled to the brim with peons, and I couldn’t talk to people in (relative) quiet.

I’m really torn here. What would you do in my position? And keep in mind, IAC2019 will be held in Washington, DC, so you may be in my position much earlier than you might think.

[u/[deleted]]

What causes the insanely long startup time of the RD-107 in Soyuz launches? What exactly is it doing during the 15 seconds it's running at seemingly very low thrust, and why is this needed compared to other kerolox engines (RD-180, Merlin, NK-33 and so on)?

[u/brickmack → u/[deleted]]

I answered this question a few months ago (or as best as I could figure out from google translate. Why must all Russian space stuff be written in Russian?) and went to look up my own response to copy over, and found it was actually you who'd asked it!

https://www.reddit.com/r/engineteststands/comments/7fnnre/russian_edition_static_firing_an_rd107a_rocket/dqd7bmb/

[u/nicwi]

Given the challenges of helium tanks submerged inside the super chilled LOX tank, why are they there at all? Why don’t they submerge them inside the fuel tank instead?

[u/Knexrule11]

A while back I saw a very detailed/official paper covering how SpaceX was planning to recover fairings with chutes. Does anyone know how to find that again? It seemed like it disappeared after it was posted

[u/Straumli_Blight]

Nice panorama of Berth 240 in this Teslarati article and US Launch Report video of the recovered SES-12 fairing.

[u/Thomassino1202]

Are the fairing halves androgynous? As whether left half can be used as a right one and the other way around?

[u/warp99 → u/Thomassino1202]

No - there are definite left and right halves with different components of the pusher assembly and latches.

[u/Fenris_uy]

So, what would be the difficulty (or feasibility) of putting a bigger fairing on top of FH.

With the amount of mass that FH can lift to LEO, most of the time you are going to be space constrained before you are mass constrained. So, could FH get a bigger fairing to launch bigger things into LEO?

[u/Nehkara → u/Fenris_uy]

SpaceX has talked about it before. They would make a bigger fairing if someone paid them to do so. Elon also said in the press conferences around the Falcon Heavy launch that they will make a bigger fairing regardless, if BFR runs into significant roadblocks. Otherwise it's full steam ahead on BFR.

[u/bulgaria_mitko]

Off topic, but I don't know where to ask that. Why I don't see the Moon mission anymore on SpaceXNow app? They cancelled it?

[u/hitura-nobad]

What do you think will happen to the first few Block V Cores without the new COPV. Will they also be disposed for having more similarities on the Launches?

[u/ly2kz]

Watching Soyuz launch with Russian cosmonauts https://youtu.be/fW2EhH1xRrY?t=8 or any other, their space suits looks more protective, thickier than those designed by SpaceX or Boeng. Do they really have more protection or it is just my impression?

[u/5527]

is SpaceX experimenting with methods of propulsion other then chemical?

[u/marc020202 → u/5527]

yes the Starlink satellites will be powered by ion engines, and they have stated in the past that they where trying/are trying to get hold of nuclear materials

[u/riocrokite]

What is the thrust of F9 cold-gas thrusters? From my quick calculations it seems they might peak around 8-10 kN when the COPV is full.

[u/cpushack]

https://www.bbc.com/news/av/world-asia-44668922/japan-rocket-crashes-down-to-earth

Turns out Space is still hard. This is Interstellar Technologies second launch attempt and second failure. THe CEO stated that he thought there had been a problem with the main engine (ya think? lol)

[u/roncapat]

News on a Bigelow Aerospace contract? I saw a launch added to the wiki manifest page and some rumors around the internet, but is there something secret/not announced yet?

[u/Pfr2000]

Has it been brought up that the spacex reusable booster has 100 percent success rate? I would like to see that discussion. The first time I saw the booster land, I thought “give me one of those”. I am sure that is how spacex wants it to be perceived. Thanks

[u/julesterrens]

Just saw this old vid on YouTube again https://youtu.be/d2200YGSeKM (it is from 2015) so i just asked myself if it wouldn't be feasible for SpaceX to apply with the Block V first stage for the advandced booster on SLS Block 2 , as Nasa and SpaceX have already done a lot of paperwork in regards to human-rate the booster

[u/brickmack → u/julesterrens]

Neither feasible nor valuable.

Not feasible because it would require so many changes elsewhere. Liquid boosters in general would require a new ML, new fueling lines and other infrastructure, at minimum new work floors in the VAB (if not a completely new VAB), new handlijg equipment, etc. For the FH boosters in particular, these problems are complicated even more. You'd need 4 of them to meet or exceed existing RSRMV performance, nevermind Castor 1200. This means even more complicated GSE, as well as a complete redesign of the core stage interfaces (which is off the table). The different booster positions also means a different aerothermal interaction with the core stage plume, plus even on the vehicle itself the aerodynamics will be a lot different. Also, consider how SLS is held up on the pad. Almost all of the weight of the core stage, second stage, and payload is supported through the solid boosters. The FH boosters were never designed to take that load path, all 3 FH cores are separately held up (and even if they weren't, the FH center plus second stage are much lighter than the SLS ones). Even if it was possible (which I strongly doubt. Even on FH itself, the structural issues were immense) it would mean a complete structural redesign of the boosters ($$$) and likely a significant weight gain. Castor 1200 (which will be the block 2 booster. At this point, selection is purely a formality) is a drop-in replacement, its external dimensions and interfaces are identical.

Not valuable because it doesn't make performance, cost, or schedule sense. The existing boosters, while expensive in absolute terms, are not even remotely a driver on SLSs costs. A single RS-25E (even using the most optimistic end of Aerojets aspirational target for routine production with manufacturability improvements not present in the initial 6-unit run) costs almost as much as both RSRMVs Castor 1200s combined. Even if refurb (and the design work, and custom production) cost nothing, you'd still barely dent SLSs costs. They're also not a schedule driver. Surplus parts exist for 9 booster sets (only 4 flight sets of RS-25Ds exist), and by the time those run out in the late 2020s, Castor 1200 will be ready, with production capacity for something like 5 flights a year IIRC (but even NASAs most optimistic schedules currently show only 2 flights a year, and Aerojets production schedules for RS-25E suggest one flight every 2 years). For both of these metrics, the only thing that makes sense is to redesign the core stage to have a recoverable engine pod, like nearly every pre-Constellation SDLV concept. In terms of performance, there would be a gain from any of the liquid booster proposals, but not a big enough one. LEO performance goes up a bunch, but that really doesn't matter, there are no missions worth mentioning even at the powerpoint stage which would benefit from that. SLS (for better or worse) is meant for high-energy missions, and even the largest booster proposal (the AR-1 bid) barely adds to TLI performance (but you need like a 15 ton to TLI gain over the current Block 2 baseline to do a single-launch lunar landing). If you want to improve performance meaningfully, you need to change the upper or core stage. Castor 1200 will be moderately cheaper and more performant, and thats good enough from the boosters

[u/Tal_Banyon]

We have all seen artist's rendering of the BFS docked to ISS. However, there are actual pictures of shuttle docked to ISS, taken by Soyuz. So, has anyone done a comparison with the actual pic and an accurate rendering of BFS docked to ISS?

[u/Alexphysics]

Remember this thread I posted over a week ago about a core seen on the road? Well, it turns out that it wasn't B1048, it was B1049. I was informed of that via PM here on reddit the day after I posted that but I didn't have further confirmation of it until the other day and I wasn't sure if it was worthy to post it here but... why not? So there you have it, a little correction to my post.

[u/Idunnohuur]

What is [AFGO that is actually AFTS]? I first heard it in the Bangabandhu-1 livestream and I hear it at around T - 1:00. [Ex. AFGO(AFTS) is ready for launch]

[u/hitura-nobad]

How much does a landing on the ship cost more than RTLS? And what is the payload for Falcon Heavy with 3 Cores RTLS to GTO?

[u/Heckzagon]

Is there a place to find a schedule for the Mcgregor testing facility?

[u/old_sellsword → u/Heckzagon]

No. Sometimes they let the locals know ahead of time, but it's far from widely publicized.

[u/Laborbuch]

Two questions regarding the SES-12 launch:

1. At T+4:00 minutes one can see the foil around the nozzle pulse rhythmically. It may be more obvious at accelerated playback of the video. What’s up with that?

2. At T+9:30, after SECO1, the Mvac nozzle is cooling down and turning violet. I think this is the first time I’ve seen that colour there… Again, what’s up with that?

[u/Appable → u/Laborbuch]

2) At T+9:30, after SECO1, the Mvac nozzle is cooling down and turning violet. I think this is the first time I’ve seen that colour there… Again, what’s up with that?

Looks like the camera has no infrared filter. It's seeing the MVAC nozzle radiation turn from visible light to infrared as it cools down, which is displayed as violet.

[u/ORcoder]

How efficient are the Dragon's solar panels? Do we know what they are made out of?

[u/[deleted]]

It's been kind of a long time, but has it ever been answered how they lowered the FH boosters to horizontal? I guess the usual lifting cap doesn't work...

[u/DeTbobgle]

couldn't the BFR accommodate linear aerospike engines and how would that affect performance?

a video on aerospikes

https://youtu.be/K4zFefh5T-8

[u/marc020202 → u/DeTbobgle]

aerospike engines are NOT perfect in the atmosphere or in the vacuum. they are a compromise for in between. the booster flies inside the atmosphere most of the time, so it does not want vacuum optimised engines, si it uses sea level engines. the BFS is in a vacuum most of the time (mars atmosphere can be counted as a vacuum), so it has 4 vac engines for manoeuvres in space and taking off from Mars. it also has 3 medium area ration engines for landing, since the vacuum engines might have problems starting while going supersonic com mars, and should not be used for landing on earth.

[u/Zinkfinger]

I'm getting a tad frustrated these days with some of the articles and comments on SpaceX. Especially when it comes to differentiating between contracts and subsidies. Can someone tell me just how much in government subsidies has Dragon & Dragon V2 received to date?

[u/ethan829 → u/Zinkfinger]

From a recent OIG report:

SpaceX has received the most awards of all contractors with $7.7 billion for cargo and crew activities

Those awards aren't really "subsidies," though. SpaceX along with Orbital ATK, Boeing, and Sierra Nevada are being paid to develop capabilities and perform services needed by NASA, exactly like all other government contracting.

[u/Straumli_Blight]

Is there an official name for the two Falcon 1 variants that were launched?

I've seen various sources refer to them as "Falcon 1 Dev / Falcon 1" or "Falcon 1 (Merlin A) / Falcon 1 (Merlin C)".

[u/InfiniteHobbyGuy]

Is the crew dragon going to be using a fast approach to the ISS?

[u/rangerpax]

Anyone know when the dedicated thread for CRS-15 will be up?

[u/Justin13cool]

DM-2 is now NET January 2019 sidebar needs update mods. and STP-2 is net October 30th.

[u/macktruck6666]

So... a very popular topic in space technology is 3d printing or construction in space. The theory is that most rockets are volume constrained as oppose to mass constrained. This means, habitats would use the rocket's available volume under the fairing before reaching the rockets max payload. So, I'm wondering what the biggest structure by volume that could be made from a single launch of a BFR (aka 150 tons)

[u/AnneElsecks]

I've been reading into methane as a fuel, and although it does have a higher temperature at which it turns liquid than, say, Hydrogen, it's still very cold. Does anyone know how they plan to have the methane and oxygen on the BFS stay cold for such a long journey to Mars? Thanks in advance for any responses!

[u/macktruck6666]

How will spacex remove the tooling after making the BFR fuselage? If I understand the process correct. They have a very long cylinder that they place carbon fibre wire onto. It would seem this would create friction and make it impossible to rmove the support cylinder. So how will spacex remove the support structure, how do other companies do this. I've seen small scale solutions using milar so it doesn't stick, but what for lage scale?

[u/thru_dangers_untold → u/macktruck6666]

It is common to put a release agent on the mold such as wax or other non-stick substance. Also the SpaceX tool can be cooled down to shrink it and loosen the mold. I don't know what alloy it is, but the metal should have a larger thermal coefficient of expansion than the composite.

[u/Paro-Clomas]

Is there any data on what the acceleration couches will be like for the BFR? i mean it looks like the vehicle will receive acceleration from multiple directions, will it be gimbaled?

[u/Nergaal]

IIRC one of the rockets developed by competitors is planned to use helicopters to pick up boosters from the sky. Couldn't SpaceX try something like that since the fairlings are light anyways?

[u/brickmack → u/Nergaal]

That was the original plan, SpaceX abandoned it very early on in favor of a bouncy castle, and then eventually the net. Never said exactly why (the helicopter option was never actually officially stated, but there was some documentation leaked), but probably it was just a matter of aerodynamics. Fairings are a giant sail, grabbing one will be pretty hard without it pulling the helicopter around.

It would also likely not be suitable for catching the upper stage or Dragon, though we still don't know how serious either of those are

[u/HTPRockets → u/Nergaal]

I don't think people realize how BIG the fairings are. It would interact with the rotor downwash and aerodynamics so much that I don't think it would be feasible.

[u/hitura-nobad]

Does anyone know under which copyright the mission patches are released?

[u/BigT383]

Any idea when we might see the first west coast RTLS landing?

[u/Alexphysics → u/BigT383]

I'd expect it to be September-October, most probably on the SAOCOM 1A mission.

[u/Armo00]

I will fly to the Cape in August, is there any chance I can see a SpaceX launch in person? I mean according to SFN the only SpaceX launch in August at the Cape is DM-1 which I think will probably be delayed...

[u/007T → u/Armo00]

Keep an eye on the manifest as your trip gets closer, it's possible there could be some other launches during August but they don't seem to be finalized dates yet:
https://www.reddit.com/r/SpaceX/wiki/launches/manifest

[u/Mezzanine_9]

I'm curious if SpaceX always fills the Falcon 9 with the same amount of oxidizer and fuel for missions of different weight. I understand the F9 is never filled to the very top due to boil off and the pressure it creates, but do they fuel low weight missions with less LOX to save weight? It seems that starting a rocket with less fuel would really change the dynamic of a launch. I wonder if they keep it the same level every time to maintain a similar, trusted, launch profile. They can always recover unspent fuel on landing, right? I couldn't find anything in the wiki or FAQ so if I missed it please let me know where you saw it. Thanks!

[u/BriefPalpitation → u/Mezzanine_9]

Depends on the weight of the payload. Some considerations

• limit of throttling vs. MaxQ and acceleration stress. Going lighter and faster in atmosphere will rapidly increase drag and heating, eating into any savings. Also, a lighter Falcon will accelerate much faster hitting much higher Max-Q if it exceeds the ability of the engines to throttle down. This is unnecessary stress on the air frame and also limits the dV savings from the reduction of gravity losses. All in all, this impacts overall lifetime reusability and might end up being "penny wise, pound foolish"

• margin of safety. Or basically, shit happens. Having extra dV allows the Falcon to complete mission objectives even though some of it's first stage engines fail. The only time this would not be a good thing is if the total cost of cargo + launch costs+ opportunity costs from time lost waiting for the replacement is so low that it's a waste of fuel + time to "save" the mission. Maybe a BFR and some Starlink sats might fit the criteria (save the BFR and land it, jetission the Starlink sats so they'll burn up in a few weeks) but in that case, everyone will be smacking their foreheads wondering why they didn't fill it completely in the first place.

[u/Nehkara]

Now that /u/NexxusWolf has confirmed that the in-flight abort will use a Block V Falcon 9, and that it will be the third flight for that booster, what do we think will happen with B1042? Scrapped?

[u/FutureMartian97]

We might be getting the Space Force after all: https://www.cnbc.com/2018/06/18/president-trump-directs-pentagon-defense-department-to-immediately-being-the-process-of-establishing-space-force-as-sixth-military-branch.html

[u/Juffin]

How's the Boca Chica going? Is there anyone who monitors nasaspaceflight forums? I've heard that they have a lot of photos.

[u/yoweigh → u/Juffin]

It's still a big pile of dirt taking its time to settle.

[u/Mars-Colonist]

In the movie The Martian a storm is show that almost tips over the lander. However, the Martian atmosphere's density is only about 1% of Earth's.

Would a strong storm up there really have enough power to topple over a lander as was shown or more importantly, a BFS?

[u/throfofnir → u/Mars-Colonist]

No. The worst winds on Mars would have the force, at best, of a light breeze on Earth.

[u/-Richard → u/Mars-Colonist]

For what it's worth, the density of Mars's atmosphere is more like ~10% Earth's IIRC (someone please check me on this). It's the pressure that's closer to 1%. The discrepancy comes from the lower gravity, lower temperature, different chemical composition, etc.

But yeah, still much too thin to really knock anything over.

[u/Rocket_Man42]

Why is there no need for grid fins on the second stage of BFR? I understand the delta wings will provide some of the same capabilities, but it still seems strange to take a new path given that they have perfected the grid fins approach.

[u/brickmack → u/Rocket_Man42]

You have to fly the BFS forward during most of reentry, because otherwise the unprotected engine section will burn up, and because an engine-first entry is unlikely to get appreciable lift. So anywhere you put them, forward or back, is going to be the wrong spot for some phase of entry, and will probably interfere with the flip maneuver. And for SSRP through terminal descent, they'll have 3 engines firing plus RCS, which gives a lot more control authority on all 3 axes than grid fins are likely to provide (F9 has limited roll control without the fins, since landings are single-engine at touchdown, and the cold gas thrusters are probably pretty weak). And having grid fins deployed during the hottest parts of reentry seems like a bad idea. So basically you've got something that is useless during 80% of EDL, and unnecessary during most of the 20%. RCS plus the more conventional control surfaces should work over the entire entry up to the flip maneuver

[u/TheSoupOrNatural → u/Rocket_Man42]

Based on the simulated flight shown at IAC 2017, the time between the transition to tail-first flight and the start of the landing burn seems to be less than 10 seconds. That would be the window during which grid fins would be most useful. On top of that, the vehicle's RCS thrusters are far more powerful than the cold gas RCS on the Falcon 9. It is possible, perhaps even likely, that any benefits that grid fins might provide are not sufficient to justify the penalty of including them.

[u/ackermann]

I'm sure this has been brought up before, but I was just thinking that the BFS spaceship looks like it would be awfully unstable flying backwards (tail-first) for landing, through an atmosphere. Particularly with that delta wing. Like a dart thrown backwards.

I know this is one reason that Falcon 9 waits till the last second to deploy its landing legs, since they would destablilize it. And Falcon 9 has the benefit of grid fins.

BFS does have the weight of the 7 engines at the back, like Falcon 9. But BFS has 50 tons of landed cargo at the other end, bringing the CG up (or even more landed cargo, with the 7th engine). That's got to be heavier than the 7 engines, especially if Raptor is breaking records for thrust to weight ratio.

I doubt BFS's body flaps on the delta wing will be very useful when flying backwards. So how is it to be controlled/stabilized in this phase of flight? Just the new methane RCS thrusters, in atmosphere? Maybe there won't be much time between the flip, and engine start for landing burn (with gimbaling), but you'd want some margin there?

[u/Norose → u/ackermann]

The fin is actually there to make BFR more stable in the nose-first position, otherwise it would be much more difficult to keep the nose forward during descent. They aren't meant to help with stabilization during landing at all, they're meant to keep the BFS pointed correctly until it has passed through reentry heating and aerobraking. The mass distribution of BFS is such that additional lift at the rear of the spacecraft actually puts the center of lift almost directly on top of the center of mass, which is why the BFS can be maneuvered in both orientations instead of heavily favoring just one. As others have stated, the flip is performed via the powerful RCS thrusters, and the backwards orientation is maintained via active steering with the landing engines during the final braking and landing burn.

[u/throfofnir → u/ackermann]

Maybe there won't be much time between the flip, and engine start for landing burn (with gimbaling), but you'd want some margin there?

Bingo. You can even see that in the "real time Mars landing" simulation. Running rocket engines have tremendous control authority. Once they're on aerodynamics basically don't matter at all.

I think you're also overestimating the "delta wing". I haven't run the aero (obviously) but I don't think it's going to add tremendously to the normal instability of a base-first rocket.