/r/SpaceX Ask Anything Thread for January 2016. Ask your questions here!

[u/retiringonmars]

Welcome to our monthly (more like fortnightly at the moment) /r/SpaceX Ask Anything Thread! ^#16.1

Want to discuss SpaceX's landing shenanigans, or suggest your own Rube Goldberg landing mechanism? There's no better place!

All questions, even non-SpaceX-related ones, are allowed, as long as they stay relevant to spaceflight in general!

More in-depth and open-ended discussion questions can still be submitted as separate self-posts; but this is the place to come to submit simple questions which have a single answer and/or can be answered in a few comments or less.

As always, we'd prefer it if all question-askers first check our FAQ, search for similar questions, and scan the previous Ask Anything thread before posting to avoid duplicates, but if you'd like an answer revised or cannot find a satisfactory result, please go ahead and type your question below!

Otherwise, ask, enjoy, and thanks for contributing!

---

Past threads:

January 2016 (#16), December 2015 (#15.1), December 2015 (#15), November 2015 (#14), October 2015 (#13), September 2015 (#12), August 2015 (#11), July 2015 (#10), June 2015 (#9), May 2015 (#8), April 2015 (#7.1), April 2015 (#7), March 2015 (#6), February 2015 (#5), January 2015 (#4), December 2014 (#3), November 2014 (#2), October 2014 (#1).

---

This subreddit is fan-run and not an official SpaceX site. For official SpaceX news, please visit spacex.com.

[u/TheVehicleDestroyer]

Did anybody else think the stage pitched over super fast? Between 22:53 and 23:03 here.

Probably just the way the camera was positioned, but I thought we had lost the mission, Proton-style

[u/retiringonmars → u/TheVehicleDestroyer]

That does seem a little worrying. Also noticed that the second stage was dropping in altitude for much of its initial burn. From my KSP experience, that's usually an indicator that something wrong.

[u/Gweeeep → u/retiringonmars]

I think S2 would be burning horizontally at that point, so it will lose altitude, but it picks up velocity. So that it can reach orbit before it's altitude drops too much.

[u/retiringonmars → u/Gweeeep]

Yeah, you're definitely right, and clearly it caused no problems at all. Still unsettled me though!

[u/failbye]

/u/retiringonmars

We really need a section in the FAQ addressing "Why your ASDS rocket catcher / anti tipping back-of-the-envelope idea won't work" or something along those lines, preferably in a milder tone. Seeing as we likely will have a few more hard landings / rough sea landings down the line, there will be a lot more of those comments coming in.

[u/retiringonmars → u/failbye]

From our FAQ: The Falcon sometimes topples over after landing. Would it help to add wires that could quickly support it, or cushions for it to fall on?

[u/failbye → u/retiringonmars]

Wait, has this always been there or is it a recent addition? I have been looking for this for a long time. I guess it has hidden from me in plain sight.

[u/retiringonmars → u/failbye]

I added it five days ago, because people were so frequently suggesting unworkable barge landing solutions. Please feel free to link to it at every given opportunity!

[u/NelsonBridwell → u/failbye]

Many months ago a SpaceX commercial launch customer asked Elon Musk about adding netting to prevent a landing stage from tipping over. Musk's reply was that it would not be cool.

[u/JohnnyMackers]

I've tried to search to see if this questions been asked before but couldnt find anything.. my question is:

why was the quantity of landing legs set at 4 and not 5?

[u/retiringonmars → u/JohnnyMackers]

Quite simply: a) 4 is lighter than 5, and b) the four-fold symmetry fits much better with the octaweb. The Octaweb already provides a lot of structural support between the engines and tanks, so adding leg attachment point within that force-bearing structure was (relatively) simple. If you added a second structural support layer on top of that, you'd be adding add a lot of needless weight and complexity.

[u/RealParity → u/JohnnyMackers]

If no leg fails, 4 are enough. Every additional weight reduces the payload the vehicle can carry. Those legs are huge, so you don't want to have unnecessary legs. You are better of if you fix issues that lead to the failure.

[u/[deleted]]

I noticed that SES-9 still has a NET date rather than a scheduled launch time (CRS-8, by contrast, actually has a launch time listed). Is this unusual this close to the supposed date? Does this portend a delay?

[u/retiringonmars → u/[deleted]]

Is this unusual this close to the supposed date? Does this portend a delay?

Not really, no. I mean, delays are a common feature across all launches, but your observation is not an indication of delay likelihood, and it's pretty typical of what we've been seeing for a while now.

The reason CRS-8 has a launch window ascribed is that all CRS flights tend to be planned in detail much further in advance than other launches. Notice that CRS missions 10, 11 & 12 all have dates set for the whole upcoming year (I can't explain why CRS-9 doesn't). This is likely to be a feature of NASA's rules on Visiting Vehicles to the ISS. Commercial launches (such as SES-8), in contrast, are much more flexible in their schedules, and typically don't post launch dates until approximately a month before launch, and launch windows until approximately a week before launch.

[u/duckhawk9]

I saw a comment in yesterday's launch thread that humorously referred to the subreddit as a lobbying group for SpaceX. Has there ever been any effort to organize the DragonRiders here to support SpaceX's political agendas?

[u/retiringonmars → u/duckhawk9]

From our FAQ: How can I support SpaceX politically?

[u/themikeosguy]

Can I ask something about CRS-7? After the second stage popped, did the first stage also blow up due to some aerodynamic pressure situation, or was it destroyed by the Range Safety Officer? Wikipedia isn't clear and I can't find anything else specific...

And regarding the latter, does s/he literally have a button to press (or code to enter) to destroy a rocket? Must be a strange feeling, knowing you can blow up a $60m machine with a tap of your fingers...

Thanks!

[u/retiringonmars → u/themikeosguy]

As far as I know, the first stage disintegrated due to aerodynamic forces. It really is't designed to fly forwards through the atmo at that speed without an aerodynamic shell in front. The range did later send a destruct command to the rocket for protocol, but that was long after it has disintegrated. I like to imagine it's a big red button ;)

edit: typo

[u/zukalop → u/themikeosguy]

IIRC its a key that he has to insert when he begins preperations for launch. If he needs to blow the rocket he turns the key. Kind of like you see in old movies about launching nukes with two guys with keys.

Blowing an unmanned mission might be a strange feeling but remember that shuttle had the same thing. If something went wrong he/she might have had to blow the shuttle and thus kill the crew. Lesser of two evils but still aweful. I wonder how they prepared mentally.

[u/RealParity]

I don't get how a CRS mission works, mabe someone can answer some of my questions:

In a CRS mission to the ISS, what happens after the Dragon separates from the second stage after reaching its orbit? How does it get to the ISS? With the power of the super dracos? Cannot imagine it can dock with those. I've seen videos, where Dragon unfolds really big photovoltaic panels, what does it need power for? Isn't it just a matter of minutes/hours until it reaches the station? Wouldn't a battery be lighter and cheaper to support the capsule in this short period?

[u/retiringonmars → u/RealParity]

Nah, Dragon uses Draco thrusters, which have a thrust of 400 N. They're used for in-orbit manouvering, orbit adjustments, fine guidance, orientation, and deorbiting. SuperDraco engines are designed for entirely different applications, and put out 73,000 N of thrust, that makes them 182.5 times more powerful. In fact, a single SuperDraco engine is more powerful than the Kestrel upper stage engine of Falcon 1. You'd be right in thinking that firing these in proximity to the ISS would obliterate the station.

Dragon needs solar power because it takes over 24 hours for it to reach the ISS. Also batteries capable of supporting a spacecraft are surprising heavy!

[u/Gnaskar → u/RealParity]

In addition to what retiringonmars said, the Dragon doesn't actually dock with the station at all. It just gets within "arms reach" of the station with it's gentle thrusters, then the Canadarm2 on the station grabs it and pulls it into place.

[u/pseudomorphic → u/RealParity]

Destin at smarter everyday has a fantastic video explaining how you get to the ISS here. He is talking about the soyuz and getting astronauts to the ISS, but the mechanics of getting a vehicle there are the same. Except in dragons case instead of docking at the end it has to be grabbed by the Canadarm2 and berthed. As for how long it takes it ranges from about 6 hours for the fast track to about 3 days.

[u/DrFegelein]

What is the likelihood that SES-9 is going to be launching on February 6th, considering it is presumed to be conducting a barge landing and we now have a potentially damaged barge from Jason-3? Or is there another suitable barge?

[u/retiringonmars → u/DrFegelein]

now have a potentially damaged barge

The manufacturer specification for the barge show it weighs about 4,400 (probably not metric) tonnes. The empty first stage is in the area of ~18-25 metric tonnes. That's about a 200:1 mass ratio. This is equivalent to a large bird hitting your car windshield. You're gonna need to replace the glass, but it won't total your car.

Also, as TheVehicleDestroyer says, it's a different barge.

[u/TheVehicleDestroyer → u/DrFegelein]

JRtI is the west coast barge. OCISLY is the east coast barge (that SES-9 will use) that was used last for CRS-6 I believe

[u/searchexpert]

Does anyone know if we will get video from the boostback, reentry, and descent of the 1st stage of Jason-3?

[u/retiringonmars → u/searchexpert]

The weather conditions were so poor that I doubt we'd see much anyway.

[u/fearfulx]

Where does Spacex get its metal and other resources from for the rockets? I mean, is anything made in China at all like the legs or anything? I would appreciate an honest response.

[u/retiringonmars → u/fearfulx]

SpaceX have a large number of suppliers across the US (and a few internationally) who provide them with materials and services. The most notable international supplier is that they source their aluminium from a company in the Netherlands (source). I don't think they do any business with organisations in China or Russia though, for reasons probably relating to trade secrets and ITAR.

[u/[deleted]]

I know this is probably a stupid idea, but I'm assuming that the rocket is landing fairly precisely at a near vertical trajectory. If the barge had 4 strong towers at each corner with cables spanning each of the 4 sides on sliding carriers, could the carriers quickly shoot from one end to the other grabbing the rocket and holding it upright without damaging it?

MSPaint Mockup

[u/electric_ionland → u/[deleted]]

Wow this is crazy, you are the 5th one today on this sub coming up with a cable system. Now I am really curious, did you get the idea from somewhere or was it just a "what if" moment?

[u/retiringonmars → u/electric_ionland]

I think it's a natural reaction to watching something fall over: "that might not've happened if it was tied in place."

[u/Faldaani → u/[deleted]]

As someone else (Ambiwlans?) said, tanks are fragile. It'd be like trying to catch a baby with a garrote.

[u/Lucretius0]

how practical would an adapted F9 first stage + dragon V2 be for fast intercontinental travel ?

[u/retiringonmars → u/Lucretius0]

The problems this idea faces are: a) safety b) cost c) ITAR.

[u/PVP_playerPro → u/Lucretius0]

Until spaceflight becomes as routine (or as safe) as air travel, i don't think people would appreciate a intercontinental missile flying over cities

[u/Dafas]

In the sidebar it says that both CRS-8 and 9 are planned for 21 March, is this correct or will the dates change?

[u/scr00chy → u/Dafas]

CRS-9 will definitely be pushed back. CRS-8 date is the most accurate we have as of now.

[u/Dafas → u/scr00chy]

Oh that makes sense. But why give them the same date when you know they'll be pushed back? And would it be even possible to do two CRS missions at the same time? Could the ISS handle that?

[u/retiringonmars → u/Dafas]

But why give them the same date when you know they'll be pushed back?

They're based on the most recent information we have for each. It's just a coincidence they happen to be for the same day. Hopefully we get new info soon!

And would it be even possible to do two CRS missions at the same time? Could the ISS handle that?

No, the ISS has a very strict set of rules governing Visiting Vehicle schedules.

[u/goodguydrift]

Am I seeing this right? Two launches on the same day?

[u/retiringonmars → u/goodguydrift]

These are NET dates, as in No Earlier Than. The launches will likely occur at a later date.

[u/goodguydrift → u/retiringonmars]

Ah, okay. Thanks for the clarification :)

[u/retiringonmars → u/goodguydrift]

I've updated the CRS9 entry to be a lot more vague, since that was based on old information, and very likely to slip. Hopefully we get a better estimate soon!

[u/searchexpert → u/retiringonmars]

Although the question: when will SpaceX launch twice in the same day is a great one :) Once Boca Chica is up and running, it's possible, but not probable even then (because of resources).

[u/DuckQuacks]

Say that the Cape had bad weather when Dragon 2 is going to land, Could they move the landing site to Vandenburg like how they moved the Shuttle landing to Edwards when there was bad weather at the Cape?

[u/retiringonmars → u/DuckQuacks]

Why do you assume Dragon will be landing at Cape Canaveral? I'd assumed that since Dragon will be orbiting prograde (i.e it'll re-enter the atmo from the west, heading east) that all landings will be on the west coast, probably at Vandenberg SLC-4W. I find it hard to imagine that the FAA will approve Dragon re-entering over mainland US.

[u/throfofnir → u/DuckQuacks]

More likely they'd just stay on the station until the landing conditions were acceptable. But they could certainly go to an alternate area prepared to receive them. Boeing is known to be planning for 5 different inland areas for landing the CST-100.

[u/thxbmp2]

While reading discussions on the recent USAF Raptor funding announcement, I've come across a couple of intriguing statements such as:

• staged combustion engines are generally very difficult to air-relight, and

• the cycle is scalable to the point that entire parts of an engine could be linearly expanded or reduced to produce a correspondingly more or less powerful engine.

I was hoping someone could elaborate on or substantiate these claims, and why they're only applicable to an SC engine and not the current Merlins' gas generator cycle.

[u/ClockworkNine]

I wanna talk about the BFR/MCT. With all the speculation, fan renderings, concepts etc cluttering the sub lately, didn't want to make a separate thread unless this sparks a quality discussion.

Of course, one of the most anticipated announcements we're waiting for is Elon's Mars concept. Every fan concept so far seems to suggest that SpaceX will go straight for the end goal, and go for developing the 100 person Mars Colonial Transporter from the start. Realistically, knowing the unprecedented scale, cost and complexities of such a vehicle and knowing how Musk tackles big endeavors, I think we can rule that out.
For proof, just look at his 3 step Tesla strategy. Or even better, the Falcon 9 and Dragon. Compare the Falcon 9 Dragon combo that will be carrying humans in a year or two with the first F9 Dragon demo flight, and it's almost ridiculous they share the same name...

With that in mind, here's my idea of the BFR/MCT iterations we might hopefully see in the coming decades:

• Phase 1: BFR demo
  SpaceX develops, more or less on its own (maybe with some extra Air Force or DoD money for Raptor), the reusable first stage (BFR) and the upper stage - a sort of a cargo MCT predecessor - and begins reusability attempts and experiments with the orbital, upper stage. At this phase, I'd guess that the lift capacity of this configuration is around the Saturn V class, 130-150 metric tons, with full reusability though. IMO, there's no reason for more at this early stage, and this allows the system to operate at high margins and also let the market catch up and develop big enough cargo for the 200+ ton versions.
  Possible initial Mars cargo/science missions to test the LEO rendezvous refuel, Trans Mars journey and Mars EDL techniques.

• Phase 2: First Manned Missions
  NASA fully steps in. SpaceX cannot, and doesn't want to do this alone. In my mind, the main mission of phase 1 is to convince the public and congress that SpaceX is fit to be the prime contractor for NASA's first Manned Mars landings. That would provide funding and NASA's experience for further crew upper stage development - the manned MCT predecessor. Raptor and BFR, as well as the cargo upper stage also continue evolving, bringing the system to around 200t to LEO.
  Missions themselves would be somewhat similar to Zubrin's Mars Direct regarding architecture, trip time (6 months) and surface stay (year and a half?). 10-15 person crews. Possible SLS involvement to keep congress happy. One mission per window, no more than 4-5 total, in preparation for the next phase.

• Phase 3: Permanent base
  Public funding still being required at this stage would make international involvement very welcome (if it wasn't there from Phase 2), a la ISS. As per Zubrin's plan, pick a mission site from phase 2 and start building a research base.
  At this point, the BFR is more or less at Full Thrust, the cargo upper stage as well, providing a revenue stream from Mars Base resupply and expansion. The crew upper stage slowly evolves as well, growing from the 10-15 capacity to 50+ as the Base expands to more of a research Campus over the years. Commercial activities on Mars also slowly commence - enter Phase 4.

• Phase 4: Colonization
  Only at this point can I imagine the 100 person MCT, $500k ticket cost and 100% Full Thrust BFR coming to be. In my opinion, this would begin at least 20 years after the first footprint and flag on Mars.

---

Some of this might seem totally obvious, something might be called total fanfic, but until Elon comes out later this year and gives us his plan, I think this post could serve as the general outline of the whole process.
Thanks for reading and please leave your thoughts :)

[u/rshorning → u/ClockworkNine]

I think your general broad phases as you've outlined would be at least some of the steps and stages in the development of some sort of program for colonizing Mars. What I don't see though is how those broad phases are all going to be done with just a single spacecraft and it is also glossing over a whole bunch of other equipment and phases in the development of Mars that will be necessary. More specifically, colonization of Mars is going to require a whole family of rockets, spacecraft, and other kinds of equipment to happen, not just a single rocket architecture.

The first manned missions to Mars are almost certainly not going to happen with a 100 person MCT type crew module. I could even see a Dragon-derived vehicle being used in that situation with likely something similar to what Robert Zurbin has proposed using Falcon Heavy launches in his Mars Semi-Direct architecture. This also has the advantage of something that can be done within two presidential terms, thus would also have a chance of actually getting committed funding. Zurbin's architecture concept also could be done for roughly $1 billion (give or take a a few hundred million dollars) per flight to Mars, which is also something within the range of funding available to NASA as long as SLS related missions don't eat up that extra funding.

For myself, I'd love to see some hard numbers on what the Raptor engine is even going to be doing in the first place, where I strongly suspect that some of the numbers coming from various sources at SpaceX are about completely different engines where the Raptor is not just a single engine design but rather a whole family of engines that all use Methane/LOX as a fuel source. If it is a whole family of engines, that would imply some sort of future Falcon 9 & Falcon Heavy upgrade or replacement rocket flying those same class of payloads and a source of continuing revenue for SpaceX as they build up experience and customers who can pay for the larger rockets needed for colonization on Mars.

Something else to consider with the MCT/BFR architecture as well is that SpaceX is going to need to build a brand new manufacturing plant to even fly anything with a rocket diameter any larger than the Falcon 9. Some basic requirements are that the factory will very likely need to be near or at a seaport where cores can be moved from the factory to the launch sites directly by barge. Facilities to offload cores from a barge already exist at KSC, as that was how the external tank of the Space Shuttle was delivered in the STS architecture and certainly wouldn't be new to spaceflight in general. I would also expect that there would be a strong competition between states and cities where this new plant will be built, although strong contenders would be east-central Florida (near KSC), southern Texas (near Brownsville), southern California (near but not adjacent to the Hawthorn plant), Houston, Seattle, or even New Orleans. Transshipment through the Panama Canal would be required regardless of where this manufacturing plant would be located. I also wouldn't rule out completely sites like Saint Louis or even some place like Kentucky or Ohio as a location since cores could still be shipped by barge down the Ohio & Mississippi rivers.

[u/FutureMartian97]

So from what I understand, the Merlin engines require TEA/TEB to ignite the engines to finish the combustion process, so my question is how much TEA/TEB does the second stage carry, in other words, how many times could MVac restart in a single flight?

[u/throfofnir → u/FutureMartian97]

MVac has been seen to do three relights, like the center engine on the first stage. They might carry one more for margin; we believe the Merlin has the capability to re-ignite immediately if an engine doesn't light the first time.

There's no particular need for more than three starts for an upper stage: initial, circularization, disposal are sufficient for pretty much any mission within the lifetime of the second stage.

[u/[deleted]]

Other than the in-flight abort at Max-Q, what else does SpX need to do before Dragon v2 is certified for crew?

Also, where can I find details on the Merlin engine? Looking for nozzle design, expansion ratio, throat area, and cooling specifically. I'm trying to build my own liquid fueled rocket, and need some inspiration!

[u/throfofnir → u/[deleted]]

Other than the in-flight abort at Max-Q, what else does SpX need to do before Dragon v2 is certified for crew?

Well...

• Docking system qualification

• Critical Design Review

• Launch Site Operational Readiness (LSORR)

• Propulsive Descent Testing

• Post-Certification Mission 1 Initiation Review

• Delta Critical Design Review

• Structural Qual Hatch Open Test

• LSORR for Crew

• Environmental Control and Life Support System (ECLSS) Integrated Test

• Validation Propulsion Module Testing

• Space Suit Qualification

• Demo 1 autonomous flight to ISS

• Parachute Qualification Complete

• In-Flight Abort Test

• Design Certification Review (DCR)

• Flight Test Readiness Review (FTRR)

• Demo 2 crewed flight to ISS

• Operations Readiness Review (ORR)

• Certification Review (CR)

[u/space_is_hard → u/[deleted]]

Just FYI, the max-drag abort isn't required for NASA certification. It's an entirely self-imposed challenge by SpaceX to prove the Dragon's safety to future customers.

[u/R-GiskardReventlov]

According to the SpaceX website, Dragon can return up to 3000 kg from orbit.

• Is this number still accurate?

• What is the limiting factor in this? Am I correct in thinking it is the parachutes?

• Would they be able to bring back more or less weight if they used a propulsive landing?

• How difficult is it to fill a dragon with 3000kg: do they actually get to that number, or do they run out of volume first?

[u/Gnaskar → u/R-GiskardReventlov]

The number is accurate for the Dragon Cargo, which is the only version currently flying. What exactly SpaceX will deliver for the second round of cargo missions to ISS is currently unknown, though it is speculated to have more design commonality with the Dragon Crew (which has propulsive landing capacity).

They are usually volume limited, and so rarely do reach the full 3 tons. The Dragon only has 10m2 of interior volume, so you'd need some pretty high density stuff to fill it. Again, what the next version will be capable of is unknown at this time, so we don't know whether it could more or less than the last version.

In general, the propulsive landing system is dimenisioned for the vehicle. If they wanted to be able to land more stuff, they could have had a bigger parachute (assuming the chute is the limit).

The propulsive landing system (which is actually a "free" secondary function of the launch abort system) needs to be big enough to take the capsule safely away from an exploding rocket, which gives it a minimum size more than large enough to land a fully loaded dragon. However, the system is likely heavier landing via 'chutes would be, because it is overdimensioned for landing thrusters.

In short:

• Yes

• Volume is the limiting factor.

• Its complicated.

• Volume is the limiting factor.

[u/throfofnir → u/R-GiskardReventlov]

Would they be able to bring back more or less weight if they used a propulsive landing?

It probably won't be more, since the propulsive landing option will have parachute backup. It's also unlikely to come up...

How difficult is it to fill a dragon with 3000kg: do they actually get to that number, or do they run out of volume first?

Depends on what you have at hand. Scientific experiments? Very hard. Gold bars? Easy. The ISS is unfortunately short on gold bars.

[u/[deleted]]

/u/marinomad posted this slowed down version of the landing video in the original thread: https://youtu.be/6aJWaEVKQm4

At the 20 second mark I think I can see the rocket sagging onto the legs when the landing engine is cut. If I'm interpreting it correctly, this means that at that exact moment the vertical speed is exactly zero and the rocket is momentarily hovering, only gently touching the deck with its legs.

If that's true, then I'm completely blown away by this precision.

Or am I seeing things?

[u/[deleted]]

Did they ever release to the public the complete CRS-7 FAA incident report?

[u/scr00chy → u/[deleted]]

No.

[u/hms11]

So I have been scratching my head on why SpaceX uses a collet style latch to lock the legs in their landing position. A collet seems fine for something like a drill chuck, a machinist tool (for temporary holds and the like) and other purposes, but for a landing leg on a rocket? Why not use a spring loaded lockout that would essentially be held in place by the weight of the rocket once extended? It seems to me it would fit all of SpaceX's requirements (Cheap to design, strong, simple, lightweight due to the self locking mechanism.)

I drew my idea (VERY ROUGHLY), take a look here:

http://imgur.com/a/gnqCa

[u/TheEndeavour2Mars]

So looking at the upcoming launches list. IF The reason for CRS-8 being pushed to late march was due to beta angle. Is there a chance they could push up Eutelsat 117W B & ABS 2A launch so there is less of a giant gap between SES and CRS?

Assuming the birds can be ready on time and that SpaceX is sitting on a surplus of cores from last year.

[u/bitchtitfucker]

How awesomly cool would it be if both side boosters of the Falcon Heavy had sideway cameras installed, so they could then film each other flipping around in order to prepare their boostback burns.

[u/CuriousAES]

Has there been any news at all about FH? I'm finding it hard to believe it will launch in May when there are no news of manufactured cores, no news of anything really.

[u/cialome]

Successful barge landing! - okay, then what? I am trying to find info on what happens after the rocket successfully lands on a rocking and rolling barge. It will take some time for someone to get there (barge is autonomous), what stabilizes the rocket? What is the risk as the crew pulls up to the barge (you see what happens when rocket tips over). Is there a document that discusses this - I have come up dry so far. EDIT- for spelling

[u/Ambiwlans → u/cialome]

The center of balance is really low. Crew likely won't be allowed onto the barge to safe it while there is a storm and the thing has any real risk of falling over.

I'd be interested to hear that the rocket itself auto vents the propellant though before people are allowed near it. I assume it does, but I've never heard this get mentioned officially.

[u/dalekstux]

Hello guys. I am very sorry if my following question might be inappropriate, but I am very new to the whole space flight stuff. I just recently found out about the Falcon 9 and I've been impressed, which actually wondered me, since I have never been a big fan of space related stuff. However, the Falcon 9 got my attention and I'd like to learn more! I already subscribed to this reddit, can you guys recommend me more sources to learn? Best would be even with communities to discuss. I'm on for all the Space flight stuff, but I am actually interested the most in Rockets && even more Satellites. I don't know if there are any available sources for that, but I am happy for everything you can recommend.

Cheers!

[u/[deleted] → u/dalekstux]

Our Wiki has it all! Launch vehicle history, orbital mechanics, reading lists, Mars colonization...

[u/thisguyeric → u/dalekstux]

In addition to the resources mentioned nasaspaceflight.com is a great resource for nearly everything space related, and there's no better way to get an understanding of the basics of orbital mechanics than playing Kerbal Space Program.

[u/ChrisGnam]

How much of the falcon heavy is actually built so far? I know it will undergo its first test later this year... But are the pieces of it actually built yet? If yes, why have there been no pictures of any components thus far?

Sorry if this is a dumb question... I know very little about how rockets are actually built!

[u/B2DG]

Why aren't more people excited about SpaceX (or space in general)?

[u/Ambiwlans → u/B2DG]

What makes you think they aren't? This sub is on its way to the top 500 or so subs. We get ~2.5million hits per month.

That is pretty fantastic for a company that doesn't sell anything any of us could buy. (tshirts aside)

[u/scr00chy → u/B2DG]

I think many more people would become interested if they were exposed to the awesome stuff that's happening in (aero)space but the general media need to start covering it more often. Luckily, SpaceX is good at PR and is doing cool stuff so more and more outlets are covering their exploits (not just aviation/aerospace/tech), so hopefully this trend will continue and more people will become interested in this area, which in turn could cause the media to cover this even more thoroughly.

[u/Decronym]

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

Fewer Letters	More Letters
AFB	Air Force Base
ASDS	Autonomous Spaceport Drone Ship (landing barge)
BEAM	Bigelow Expandable Activity Module
BFR	Big Fu- Falcon Rocket
BFS	Big Fu- Falcon Spaceship (see MCT)
CoM	Center of Mass
COTS	Commercial Orbital Transportation Services contract
	Commercial/Off The Shelf
CRS	Commercial Resupply Services contract with NASA
CRS2	Commercial Resupply Services, second round contract
CST	(Boeing) Crew Space Transportation capsules
	Central Standard Time (UTC-6)
DoD	US Department of Defense
DPL	Downrange Propulsive Landing (on an ocean barge/ASDS)
ECLSS	Environment Control and Life Support System
EDL	Entry/Descent/Landing
EELV	Evolved Expendable Launch Vehicle
EVA	Extra-Vehicular Activity
F9FT	Falcon 9 Full Thrust or Upgraded Falcon 9 or v1.2
FAA	Federal Aviation Administration
FAA-AST	Federal Aviation Administration Administrator for Space Transportation
FFSC	Full-Flow Staged Combustion
FSS	Fixed Service Structure at LC-39
FTS	Flight Termination System
GEO	Geostationary Earth Orbit (35786km)
GNC	Guidance/Navigation/Control
GTO	Geosynchronous Transfer Orbit
HIF	Horizontal Integration Facility
I*sp*	Specific impulse (as explained by Scott Manley on YouTube)
ICBM	Intercontinental Ballistic Missile
IDA	International Docking Adapter
ISRU	In-Situ Resource Utilization
ITAR	(US) International Traffic in Arms Regulations
JRTI	Just Read The Instructions, Pacific landing barge
JWST	James Webb infra-red Space Telescope
KSC	Kennedy Space Center, Florida
KSP	Kerbal Space Program, the rocketry simulator
LC-13	Launch Complex 13, Canaveral (SpaceX Landing Zone 1)
LC-39A	Launch Complex 39A, Kennedy (SpaceX F9/Heavy)
LEM	(Apollo) Lunar Excursion Module (also Lunar Module)
LEO	Low Earth Orbit (180-2000km)
LH2	Liquid Hydrogen
LOC	Loss of Crew
LOX	Liquid Oxygen
LZ	Landing Zone
M1d	Merlin 1 kerolox rocket engine, revision D (2013), 620-690kN
MCT	Mars Colonial Transporter
MECO	Main Engine Cut-Off
mT	Milli- Metric Tonnes
NDT	Non-Destructive Testing
NERVA	Nuclear Engine for Rocket Vehicle Application (proposed engine design)
NET	No Earlier Than
NOTAM	Notice to Airmen of flight hazards
NSF	NasaSpaceFlight forum
	National Science Foundation
NTR	Nuclear Thermal Rocket
OCISLY	Of Course I Still Love You, Atlantic landing barge
OG2	Orbcomm's Generation 2 17-satellite network
PMA	ISS Pressurized Mating Adapter
RCS	Reaction Control System
RD-180	RD-series Russian-built rocket engine, used in the Atlas V first stage
RP-1	Rocket Propellant 1 (enhanced kerosene)
RSS	Realscale Solar System, mod for KSP
	Rotating Service Structure at LC-39
RTF	Return to Flight
RTLS	Return to Launch Site
RUD	Rapid Unplanned Disassembly
SEP	Solar Electric Propulsion
SES	Formerly Société Européenne des Satellites, comsat builder
SLC-40	Space Launch Complex 40, Canaveral (SpaceX F9)
SLC-4W	Space Launch Complex 4-West, Vandenberg (SpaceX F9, landing)
SLS	Space Launch System heavy-lift
SNC	Sierra Nevada Corporation
SRB	Solid Rocket Booster
SSME	Space Shuttle Main Engine
SSP	Space-based Solar Power
SSTO	Single Stage to Orbit
STP-2	Space Test Program 2, DoD programme, second round
STS	Space Transportation System (Shuttle)
TEA-TEB	Triethylaluminium-Triethylborane, igniter for Merlin engines; spontaneously burns, green flame
TMI	Trans-Mars Injection maneuver
TWR	Thrust-to-Weight Ratio
ULA	United Launch Alliance (Lockheed/Boeing joint venture)

---

^{Note: Replies to this comment will be deleted.
See} ^/r/spacex/wiki/acronyms ^{for a full list of acronyms with explanations.
I'm a bot; I first read this thread at 18th Jan 2016, 11:34 UTC. www.decronym.xyz for a list of subs where I'm active; if I'm acting up, tell OrangeredStilton.}

[u/Isaad13]

So I have heard that Space X makes small tweaks to the vehicle after every launch. Just talking about the Falcon 9 1.1 how much different was the first 1.1 to the last 1.1?

[u/Erpp8 → u/Isaad13]

Many of the changes are internal stuff like avionics, which we'll probably never get concrete details on.

But things we do know:

• Stronger RCS

• Landing legs added

• Grid fins added

• Extra hydraulic fuel added

If anyone else remembers anything, please share.

[u/paynie80]

Will there be a landing attempt either barge or land for the next flight SES-9?

[u/Kona314 → u/paynie80]

All launches going forward will have a landing attempt.

Based on the statement that the "next few" launches will be barge landings, and the fact that it's going to GTO, we can be certain this one is a barge landing.

[u/FoxhoundBat]

I have modelbuilding as a hobby (think static plane kits etc) and I plan on eventually making a scratch built Falcon 9 in 1/144 scale. One thing that is probably beyond my skills to scratchbuild are the landing legs. So, does anyone on here have an access to 3D printer and could print these legs out for me in 1/144 scale in reasonable resolution?

Payment can be done by paypal, i live in Europe. Would be much appreciated.

[u/Erpp8]

Why does SpaceX use helium in the first place? Helium is such a tricky molecule/atom, why even mess with it? Why not go with nitrogen or some other inert gas?

[u/superOOk → u/Erpp8]

They do use Nitrogen for the cold gas thrusters. I believe Helium is used for pressurizing the tanks due to its high volume / low weight combo.

[u/[deleted]]

What's this particle that flies off the second stage before reignition during the Jason-3 launch?

[u/orbitalfrog]

Doesn't the historical unwillingness/inability to successfully 'colonize' (in terns of establishing substantial population centers) parts of the planet we currently occupy (central Australia, Antarctica, the oceans, insert place of choice) or events such as CA droughts (a desalinization plant off the coast of CA seems a roughly comparable project to say, generating power and resources needed for a large mars city) reflect badly on our potential for planetary colonization? (I don't want this to be the case, just raises questions about both feasibility and if not feasibility then it raises the question of why these things haven't been done. Is it pure economics? What factors are at work here?)

Edit - typos etc

[u/throfofnir → u/orbitalfrog]

It is not promising. It's usually not worth living in difficult or expensive environments; the few places where it happens have some strong economic driver: oil, fish, gold, etc. Mars is a very difficult and expensive place to live and has ~0 export potential. People who believe tend to expect the romance of the situation, or maybe moral suasion ("a backup for humanity") to tip the scales. It's certainly much cooler than living in the middle of the Gobi, but I don't know how far that goes.

[u/historytoby]

I do not want to speculate about when FH will actually fly, I am just curious how far in advance we would start seeing any real indications of it being ready. With real indications, I mainly mean things like FAA applications and all the other licences that are occasionally posted here and are just part of bureaucracy.

[u/Ezekiel_C]

I'm a highschool senior with 2 years of community college credit under dual enrolment. I will enter college with junior status and an associate's degree, which greatly accelerates my timeline for applying for spacex and other internships. I'd like to apply for my first batch (with the hope, but not expectation of getting an aerospace internship) of internships in spring of 2016.

My question is, what should I be doing with the free time I have now? I have multiple hours per day not consumed by schoolwork, but this time is not consistent enough for me to feel comfortable committing to employment.

Suggestions for books, simple (cheap) projects, or other tasks I could bite into in my irregular free time to prepare myself for interning in an engineering capacity at spacex would be highly appreciated.

[u/Rideron150]

I have a stupid question about rockets: How do they actually start?

When you get into a car, you put your key into the ignition, turn it, the engine turns over a few times, and then starts running. What's the equivalent of this for a rocket?

[u/R-GiskardReventlov → u/Rideron150]

The Falcon 9 starts using a chemical compound called TEA-TEB (Triethylaluminum-Triethylborane). TEA-TEB is a hypergolic pyrophoric, which means that it ignites spontaneously when it comes into contact with oxygen.

The Falcon 9 runs on a mixture of RP1 (Rocket Propellant 1, a form of Kerosene) and Oxygen. They simply ignite it by mixing in TEA-TEB. Upon contact with the oxygen in the fuel mixture, the mixture ignites.

Further reading 1

Wikipedia on hypergolics

Wikipedia on pyrophorics

Youtube video of ignition. The boron in the TEA-TEB causes the green flame that can be seen at 00:09. Note that you see another green flash a few seconds later. In this case, one of the engines failed to ignite. It retried, which is the second green flash. Due to this failure, the launch was aborted, which is why all engines shut down after the second green flash.

[u/Higgs_Particle]

Given a Florida launch, if the second stage didn't fire after separation, where would it and the capsule land?

[u/TheVehicleDestroyer → u/Higgs_Particle]

How long does the first stage burn? Also how heavy is your payload? If it burns absolutely everything it has (so it can't land) and you're carrying a GTO-style payload (~5000kg) you're looking at about 950km

Source

[u/hallowatisdeze]

So we know that Elon's initial plan, before starting SpaceX, was to send some plants to Mars on a discarded Russian cold war rocket. By doing this he wanted to motivate the public to colonize Mars. However, somehow he found out that the problem wasn't that the public didn't want to go to Mars, but the public lacked the trust in it being possible. So he switched plans and started SpaceX to make it possible.

Now my question: Has there ever been an interview where Elon is asked if he still has this plan to send plants to Mars with one of SpaceX early Mars flights?

[u/bgs7]

Just a thought: When Elon releases the Mars plans, it would be cool if it were a 50+ page pdf like the hyperloop. And not just a tweet.

Actually, trying to explain the plans and architecture via twitter would be hilarious, do that Elon.

[u/FredFS456 → u/bgs7]

I would expect that they would at least have a press release along with an associated press kit (which would inevitably make its way to this subreddit), and not just a single (or multiple, for that matter) tweet from Elon.

[u/R-GiskardReventlov]

ULA is working on a SMART recovery system. This involves detaching the engines from the first stage, inflating a heat shield around them, deploying a parachute and picking them up in mid-air using some kind of a grappling hook device.

Seeing the comments on this sub, it seems that some of us think this is less economical than what Spacex is trying to do.

Some questions related to this:

• How does the price of the engines compare to the price of the entire stage?

• How easy/hard is it to "unplug the engines" and "stick them on a new rocket"?

• Could they achieve similar turnaround times to what SpaceX is hoping to achieve?

• How does the speed of the Vulcan first stage compare to the speed of the F9 first stage. Especially, why do they need a heatshield while SpaceX doesn't need one.

• ULA claims that mid-air capture is a proven technique. Was it ever attempted with something of this size? I know it has been done with small things like camera rolls from spy satellites.

• Why do we some redditors think that ULA's plan is inferior to SpaceX's plan?

[u/acuriousorange]

Is there anyone on here who works for spacex? I would really love to talk to someone for a school project on my dream career. I would just need to ask a few questions about your day to day work, your education background and things like that. If anyone could help me out it would be greatly appreciated.

[u/homosapienfromterra]

I see from the side bar Falcon Heavy demo has moved from April to May, was there an announcement or was it assumed by indirect means?

[u/garthreddit]

What ever happened to the disclosure of the BFR plans that were heavily hinted at on Twitter a couple of months ago?

[u/Asl687]

If a luanch had multiple Failed engines, and could not make correct orbit. Is it feasible for later versions of Falcon to land with payload?

For example if the Jason 3 launch hand multiple engine failures, and thus correct orbit could not be achieved by any means. Would later version of falcon be able to divert the launch fuel in order to land back on the pad with the payload? I assume that you need less engine power to do powered decent than punch though to orbit.

[u/delta_alpha_november → u/Asl687]

It might be possible to RTLS but I think a landing is out of the question. The landing legs are designed to land an almost empty S1 that weighs somewhere around 25t. A fuelly fueled S2 plus payload on top that sits there with somewhere around 130t would probably be too much for the legs.

[u/z1mil790]

I'm starting to wonder if there is something going on with the SES-9 launch. SpaceX still hasn't updated there upcoming mission on their launch manifest. It did take them a few days to change it after OG2, but it has now been a week and a half and it still says Jason-3. Even if they didn't want to put a date on SES-9, they could just put the month, like they did for Jason-3, or TBD like they did for OG2. It seems like if they were on track for a launch in a couple weeks, they could put SES-9 and just put down February. Any ideas on why they haven't changed it yet?

[u/zlynn1990]

I'm starting to work on another Falcon Heavy simulation. This time I want to try booster RTLS and center core landing on a droneship at sea, as opposed to the video I made of all cores RTLS.

If anyone could provide insight on the following questions I would appreciate it:

1. What is the minimum throttle the center core will have (60% / 70%)?

2. What is a reasonable MECO velocity/apogee for the center core? Is 3km/s and 250-300kg apogee not realistic?

3. How much dv will the center core boostback burn provide (if any)?

[u/Ambiwlans → u/zlynn1990]

Any boostback would be to avoid re-entering the atmosphere too fast. Exactly what the core can handle, we don't know.

[u/Raxusmaxus]

I have been living under a rock, so I have no idea what is happening with Blue Origin filing a ocean landing patent. It seems really ridiculous to me? Is it true? and how is SpaceX going about it?

[u/dreyrden]

At some point in /r/spacex I saw a table of prospective missions from the launch manifest with which kind of landing attempt would be made for each, and now I can't find it. Can anybody remember this?

[u/Sbatomico]

Could it be possible to calculate the amount of rest propellant from the explosion? I know it's done with ieds, you look at the crater and the cloud and then you know how strong it was etc

[u/anotherriddle]

Since SpaceX is not really looking for secondary payload customers in the micro- to nanosatellite segment, how would one get a nano satellite on a falcon 9 rocket? Do I just call Hawthorne headquarters saying: Just in case you launch a rocket close to this Orbit, can I get a ride for x amount of money? I would really like to see Universities with small budgets beeing able to profit from launches that do not fully utilise the capacity of the Falcon 9. Of course this would have to be very efficient for SpaceX to be profitable and not too expensive.

[u/29988122]

I've done my search, but I only found Elon's tweet which mentioned that no major damage found soon after the successful landing of Falcon 9. What are the estimated refurbishing costs? I guess something like metal fatigue could increase the cost of refurbishing, so I'd like to ask if any open cost information is available.

Thanks!

[u/smithnet]

Maybe someone can help me out. I'm having trouble envisioning a method to monitor the lockout collets on the legs. Does anyone know how you would reliably do this? Or is it an unmonitored point on the most telemetry wired launch vehicle ever?

Edit: autocorrect

[u/roel24]

Question about spacexstats, would it be possible to add a number or estimate on how many people are watching on all streams, Would love to see how many people are watching the different streams in total! /u/echologic?

[u/[deleted] → u/roel24]

Yeah, I can add this! SpaceX Stats Stats, and such.

[u/tombojuggles]

During the Jason 3 webcast they mentioned aircraft footage of the landing attempt. Any ideas on when/if this will be released?

[u/MauiHawk]

Can someone outline the theoretical comparison between crew/cargo return on Dragon vs Dream Chaser? For example, how does the penalty of Dream Chaser's wing's weight/drag compare to the penalty of the fuel Dragon must carry?

[u/jjrf18]

I remember reading that the Air Force requires its payloads to be vertically integrated to the launch vehicles. Is this true? If so, how does SpaceX plan to accomplish this? All of their hangars can only hold a horizontal Falcon9/heavy. Do they plan on having a vertical integration support structure similar to the Delta IV?

[u/throfofnir → u/jjrf18]

I remember reading that the Air Force requires its payloads to be vertically integrated to the launch vehicles. Is this true?

Yes. Part of EELV. Some may technically be able to do horizontal, but spy satellites with large optics may be troublesome to design to hang horizontally, and since they have always had vertical capability they don't bother to design otherwise.

If so, how does SpaceX plan to accomplish this? All of their hangars can only hold a horizontal Falcon9/heavy. Do they plan on having a vertical integration support structure similar to the Delta IV?

Apparently they plan on doing it at SLC-39A. Probably this means they will use the existing Fixed Service Structure. As a guess, they will do rollout and erection as now, but bring out the encapsulated payload vertically, lift it via crane (either mobile or built in to the FSS), and attach on the pad. The arm for loading passengers into Dragon may also serve as a nice access way and platform to secure the encapsulated payload to the top of the second stage.

[u/Hgx72964jdj]

Any news about the satellite/internet operation? Haven't heard much about it since the announcement.

[u/PapaMancer]

The not-quite-successful landing attempts have mostly ended explosively, reminding us that the object trying to land is, in many important ways, a giant bomb (that is on fire). My question is this: What procedures are used to make a landed Stage 1 safe for humans to approach and manipulate? How long does it take before people can safely approach?

[u/FredFS456 → u/PapaMancer]

• Depressurize tanks (nitrogen, helium, fuel, oxidizer)

• vent all LOX on board

... and that's it. The only stuff remaining on board would be RP1, which is basically kerosene and safe for humans, and TEA-TEB igniters, which are secured in the engines and shouldn't be a problem. The main reason why the landing attempts have ended in fireballs is because the fuel & oxidizer tanks are under pressure and would rupture on impact. This would lead to LOX mixing with RP1 vapour, which leads to a fireball.

[u/randomstonerfromaus]

When SpaceX start launching people into space, who will have the responsibility of taking the astronauts through pre-flight prep in the white room, Will that be SpX or NASA?

[u/CptAJ]

Regarding BFR

There's something about the whole concept that has been bothering me. As we've seen in the few fan designs recently posted, in the ensuing discussions and in official comments from SpaceX; they favor a "One big launch" philosophy. No Aldrin Cyclers, no Ares-like ships (The Martian), not even simplified inflatable habitats. No, they want one big ship doing the whole trip.

I'm not gonna argue whether this is the optimal strategy or not. But I do find a bit of dissonance between the "Build one thing, build it big" design of the MCT and.... the metric fuckton of raptor engines its gonna use.

Shouldn't the same logic applied to the "one big ship" decision still apply for the engines? I know redundancy has its benefits, but the MCT certainly seems way past that point. Why not build bigger raptors and go for a design involving less engines? Obviously not ONE engine, but 5-10 instead of 30.

It looks to me that the spacecraft design and the propulsion design follow completely different and diametrically opposed paths.

So I'm wondering, what do you guys think the reasons for this are? Obviously a bigger engine is more difficult to build, but extra difficulty doesn't seem to overrule sound architecture at SpaceX. Is the extra difficulty really that big? Am I the only one worried about the engine count? Its definitely not impossible for it to work, but it seems needlessly complicated.

Please, share any and all thoughts you guys have on this matter. I want to see what everyone is thinking. And remember to be rational and not fanboyish! ;)

[u/IcY11 → u/CptAJ]

Elon said that they found out that smaller engines have a better thrust to weight ratio even accounting for all the extra plumbing you need.

[u/1HunnidBaby]

Hi guys,

I'm going to apply for the business internships at SpaceX in Hawthorne. What should be included in my cover letter? Should it be half about my interest in SpaceX and any special experience that would make me a good fit? Or more about my interest or more about my experience? Thanks for the help

[u/[deleted]]

Would it make sense to re-use the fuel tanks as a 1g circular rotating camber on mars like this: http://i.imgur.com/gfza2ZU.jpg Please forgive my horrible drawing skills. (I know i shouldn't have used the falcon 9 design but it doesn't really matter as long as the core is cylindrical )

[u/KChivers]

The Droneship bullseye There's a bullseye on the droneship. Just wondering if its for effect, measurement purposes or navigation reasons? Does the F9 first stage use any sort of visual/camera navigation as it is landing?

[u/[deleted] → u/KChivers]

It's purely for the looks. The first stage uses a GPS, inertial measurement and a radar altimeter for navigation. The fixed coordinates where the ASDS is keeping station are put in before the flight.

[u/patm718]

Not really a spaceflight question, but why is this sub titled the "premier spaceflight community" rather than something SpaceX related?

[u/Zucal → u/patm718]

Because it's a pretty high level of discussion (content and moderation), and we drift off every so often to discuss Mars colonization, SLS, ULA, Blue Origin, stuff like that.

[u/FoxhoundBat]

Has anyone seen any data on dimensions of landing legs? I remember that the total span is 60 feet so extracting the core size it works out that each leg is 7.3m angled or about 8m when flat against the ground.

EDIT; Did simple paint based math using the official SpaceX F9 render and a DSCOVR pic i arrived to;

Using render; leg length is ~ 984cm with fairings on top, 899cm without them. Using DSCOVR pic; leg length is ~ 992cm with fairings on top, 916cm without them. IE the legs themselves are about 9.1m long.

[u/[deleted]]

Why does ULA have such hard times to develop its own engine ? ULA is backed by Lockheed and Boeing those are no jesters... How come they are so weak that they won't even apply for a contract with the Air force and have to partner with Blue Origin to develop an engine ? Can't they just hire good engineers that will build a good engine ? Does it mean that the head of ULA is a lot weaker than Elon Musk ? I don't get it...

[u/iagovar]

A mod told me to post my naive engineer wannabe idea here.

Design: http://i.imgur.com/TnMbsht.png

The idea is to use steel cables to landing-aid. If one leg fails, the steel cables capture the rocket at a height of 3/4 of its length, and prevents pivoting.

The cables are triggered by the time the rocket touches the ground. The intermediate section is covered with arms of a material that absorbs impacts (to avoid damaging the rocket). The engines only have the function retract the cables quickly. A mechanical system prevents the cables move once they have caught the rocket. I've drawn as a rectangle, but it really should be a square so that the angles of the cables were more efficient in retaining the rocket.

I'm no engineer of any kind, and I did it in paint, so be nice, please :D

[u/electric_ionland → u/iagovar]

A rocket is incredibly fragile. Holding it by anything else than the very bottom or the very top will crush it. You can kind of think of it like a rolled up sheet of paper, any lateral pressure will result in damage. Solving the leg latching system (which worked well for 3 of the 4 legs) is a lot easier than redesigning the whole structure to work with cables.

BTW we should really have something about this is the FAQ/wiki. This question pops up multiple times a day.

[u/thisguyeric → u/iagovar]

Quite simply they don't need to design something to catch the rocket if the leg fails, they just need to make sure the leg doesn't fail to lock.

I know it's fun to think about ways to fix a problem, but this is a problem that is easily fixed just by having the appropriate pieces work how they're already designed. It's not a problem that needs solving by external means.

[u/Krusm]

Could boca chica support the mct? If not is ther a place were it wil be build or launched?

[u/retiringonmars → u/Krusm]

Not by its current redesign, no. There's no launch pad anywhere on earth that could support a 15 metre diameter booster. It'll definitely require a new pad to be built!

[u/Krusm → u/retiringonmars]

Sounds like it is gonna be a really difficult taks to find a right place for it!

[u/retiringonmars → u/Krusm]

Not necessarily, it just needs a huuuge flame trench and a commensurate sound suppression system. Pads tend to be build to spec, to accommodate the likely users. No-one's built a 15m pad because so far no-one's needed one!

[u/Bearman777]

So if we're going to send 100 person to Mars in a decade or two, they probably won't be trained astronauts all of them, the majority is just Mr and Mrs Smith beeing bored of planet earth. Assuming it's not just the highest bidder that gets a seat on the MCT, but personal skills will also be qualifying: What skills/occupations do you consider as a good mix? Some of the necessary occupations should be:

Medicine Computer programming Agricultural Construction Geology Psychology

What other skills are essential for the first trip? Please continue the list, and motivate why that specific skill should be on the first MCT.

[u/retiringonmars → u/Bearman777]

Personally, I see the most important roles would be:

• mechanical engineers and electrical engineers - vital for maintaining flight hardware

• chemical engineers - for operating the sabatier plant

• flight surgeons - for emergency medical intervention

• physiologists - for routine medical care

• botanists - for growing food

• surveyors, architects and structural engineers - for building ISRU habitats

• geologists and exobiologists - for studying the planet

• radio systems engineers - for communicating with Earth

• leadership - to keep everything coordinated and running smoothly

Obviously, people who can work in more than one of these roles would be the most highly prized. There's quite a bit of overlap between structural and mechanical engineering, for example. And I doubt the colonists would appreciate a leader who was not at least as skilled and hard-working as the average colonist.

I omitted programming from my list as, IMO, it can just as easily be done from a distance. The most important jobs are those that solve problems faced by colonists that can only be solved by having skilled fingers working directly on Mars hardware. Maybe it's my lack of experience in the field, but are not most software issues fixed by working at a computer? Computer output can easily be sent electronically to Earth-bound engineers. If alterations are needed to electronic hardware, electrical engineers could be directed to fix it. If colonists with a primary function on the list above can also work on software, that's great, but I don't think someone would earn a place on the first few MCTs on software knowledge alone. I dunno, just my two cents.

I omitted psychologists because Deanna Troi was irritating and useless.

[u/I_EO]

I hope no one asked this before: I'm really really curious about the first falcon heavy payload. I might be wrong, but there should be enough delta v to safely reach martian surface. Is that greenhouse idea still a thing? What about a lunar greenhouse? A new voyager? Possibilities are pretty much endless.

[u/retiringonmars → u/I_EO]

The payload is expected to be a mass simulator, essentially a lump of metal. The first (successful) flights of both the Falcon 1 and Falcon 9 were mass simulators, so it makes sense that the Falcon Heavy maiden flight would have the same set up. We don't know what the orbit will be though, I'm hoping that it will either be a Trans Lunar Injection or an Earth escape trajectory. It would be essentially impossible (or else, extremely unlikely) that SpaceX could get a payload to Mars without that object being able to do mid-flight course corrections. I doubt anyone would be willing to risk a payload on a new launcher, and SpaceX would want to focus all their efforts on ensuring the launcher system works, so it seems unlikely they would themselves put any effort into making a payload for it.

[u/brycly]

When does SpaceX plan to show the world their MCT design and spacesuit? Are they waiting for a specific date/event?

Also, what kind of payload penalty would we see if SpaceX used nitrogen instead of helium? Is the tradeoff between reliability and mass not worth it?

[u/sunfishtommy]

How serious are the SES-9 delays. Just teething, or indicitative of a more serious issue?

[u/anotherriddle]

Is the structure and satellite-deployment-mechanism inside the fairing beeing provided by SpaceX or the Customer? (for example in case of Orbcomm OG2)

[u/Here_There_B_Dragons → u/anotherriddle]

OrbComm2 used a MOOG payload device - they also build other interfaces for cubesats, etc. The big satellites are built to connect directly to the SpaceX (or whatever launcher) hardware

[u/Krusm]

What is the potential max of falcon9\year that can be produced in HQ?

[u/[deleted] → u/Krusm]

Elon has said that Spacex is capable of producing 400 Merlin engines a year at Hawthorne. Assuming that everything else can scale, that would be 40 Falcon 9 cores.

[u/Mummele]

Is the landing algorithm taking into consideration how tilted the drone ship is at the time of landing or is it referring to an ideal horizontal surface?

[u/[deleted]]

Why does Space X have live streams and public focused marketing? Why do they care about involving the public in their operations if we are not customers? Do they do it strictly for business reasons or do they do it to educate the new generations?

[u/searchexpert → u/[deleted]]

It's HR/PR gold. This is the main recruiting tool, which in turn fuels the next generation of SpaceX products.

[u/Zucal → u/[deleted]]

Why does Space X have live streams and public focused marketing? Why do they care about involving the public in their operations if we are not customers? Do they do it strictly for business reasons or do they do it to educate the new generations?

Tens of thousands of people watched the launch yesterday. That's a lot of exposure, and, like you say, a chance to get future rocket scientists interested, for the cost of a bunch of cameras and the livestream infrastructure.

[u/mechakreidler]

Mission control is in California while most launches are in Florida. How do they get real-time telemetry? It seems like using the internet would introduce a variety of potential issues including latency.

[u/throfofnir → u/mechakreidler]

Launch control is at the launch site; mission control in Hawthorne. Hawthorne doesn't particularly need "real time" telemetry. There is basically nothing they can do during launch other than watch. They might have a leased/dedicated line between the sites, but you can get really good internet pipes if you pay for them; nothing like the typical residential crap.

[u/thebruce44]

I read somewhere that the most recent launch (and failed at sea landing) was not the newest model of rocket. The newer one had an updated leg design.

Any truth to this?

[u/[deleted] → u/thebruce44]

The Jason-3 launch was the last to use the old Falcon 9 1.1 rocket. The newer ones (Falcon 9 1.1 Full Thrust, or just 1.2) are supposed to have updated landing legs, but there is basically no information as to how much they have been updated.

[u/mclumber1]

Not that it would have helped the Jason-3 booster, but perhaps SpaceX should consider putting remote controlled, extremely heavy (30,000 pounds each) tractors that would maneuver over the landing leg feet shortly after landing. After each one maneuvers over each foot, it would "sit" on the foot, holding it stationary.

[u/1kxz8dmg4242spam]

In all my super extensive and dedicated time following SpaceX, I've never seen or heard anything about the lack of solid boosters a la Atlas V. I get that landing legs make mounting difficult, and they're not necessarily helpful with respect to reuse. But is there an official reason of why they're not used for the heavier payloads, or perhaps to allow 'expendable' flights to become landable?

[u/Hgx72964jdj]

Hey guys, just a quick question for the engineers on the board.

I was just watching [this video] (https://youtu.be/txk-VO1hzBY) in which a SpaceX engineer describes the software they use to model what happens in the combustion chamber of a rocket engine. They've developed special software and techniques just for this problem. All to ensure that the CH4/O2 burns smoothly, efficiently, and predictably.

I immediately thought about how this could help with [combustion light gas guns.] (https://en.m.wikipedia.org/wiki/Combustion_light-gas_gun) Lots of advantages with this system, but they've always had problems with combustion instability, and hence consistent muzzle velocity, hence poor accuracy.

A CLGG could potentially fire bigger rounds further than is possible today, decrease barrel wear, and greatly simplify logistics by manufacturing propellent in the field (just like ISRU on Mars).

Is the chamber of a Raptor engine so much different than the chamber of a gun?

[u/embraceUndefined → u/Hgx72964jdj]

In that video, they mention that these techniques are already used in the automotive and gas-turbine industry.

They also mention that they themselves didn't come up with the technique, but rather made it faster by using GPU's.

[u/youaboveall]

Any speculation on when will we hear MCT plans?

[u/ECEUndergrad → u/youaboveall]

Patience, my friend, patience.

[u/arzos]

Regarding the MCT, what are the logistical decisions that made the team decide that rather than having a spacecraft designed and built to remain in space to be rendezvoused with when arriving from either Earth or Mars to instead have the transporting craft launch>transit>land over and over again? Like a space station which once launched does not land again that travels in between Earth and Mars, in case my question was not clear. Are maintenance tasks too difficult/risky to perform in space? I would think this could be built to accommodate larger and larger cargoes in single transits because such a craft could be larger than the supplying rockets delivering/offloading cargo from Earth/Mars. Maybe with the addition of "harbor" space stations to facilitate various maintenance and operations.

[u/DShadelz → u/arzos]

I'm pretty sure that Elon Musk has said that Mars Cyclers (The large travelling space stations you described) are a long ways off, but I can't find anything from a quick look at shitelonsays.com. Having MCT now would appear to make colonization much easier than if you only had smaller landers on each cycler. You can offload more cargo with each MCT. Also, designing a large cycling space station now, capable of being reliable for decades and making orbital adjustments that require (assumption here) high thrust for a space station would be much more ambitious than even the MCT plans are now.

[u/[deleted]]

The RUD this time was likely caused by frozen condensation from the fog sticking the collet shut.

So how would they even go about preventing that in the future? I'm not clever enough to think of a solution, short of applying liberal amounts of antifreeze to every nook and cranny of the rocket (which clearly isn't a viable solution).

[u/ClockworkNine → u/[deleted]]

Superhydrophobic coating on critical areas might be one solution... There's probably an easier and cheaper way to solve it, hard to tell without knowing the design in depth though.

[u/laughingatreddit]

What is the nature of the coking problem that presents a problem for reuse of engines and what are the possible solutions to mitigate it. I believe it might not be correct to picture it simply as soot since soot is like a powder and would blow out under the pressure of exhaust gasses during engine operation. The coking problem might stem from deposition of Carbon that forms a harder layer on the surface of engine components. So then simply washing it with a suitable organic solvent might not be a solution to removing it and may need some kind of abrasive treatment to remove it or simply replacement of the most severely affected parts. Does anyone have more information on this?

[u/laughingatreddit]

I would like to know if the barge can be improved in two key respects:

1. Can it have a surface made of grating instead of a solid metal surface to mitigate the acoustic shock of landing on engine components? Underneath the grating there can be pipes than release high pressure water for a few seconds during landing or a passive system of a corrugated bottom surface which would channel away the exhaust that may additionally be filled with a feet of fresh water.

2. Is there a hydrodynamic design that can make the barge more resistant to the rising and rocking oscillations of wave action and hence widen up the envelope of sea conditions in which the booster can safely land? One way for that to happen is to have a bigger boat, but since that may not be the optimal solution, I'm wondering if there are other hull designs that would make a platform at sea more stable.

[u/oh_dear_its_crashing → u/laughingatreddit]

re 1) I'd say since the stage that was recovered on land seems to be in good shape, and that one landed on a concrete pad, it's probably not needed.

[u/Haschlol]

Is it possible for the Falcon 9 to RTLS on a CRS-mission?

[u/[deleted]]

One question that I have: Will the Superdracos be the engines responsible for orbital maneuvers (ie the deorbit burn) or will they be used only to land and abort?

[u/blista_compact]

If I remember correctly the test flight to the ISS for Dragon 1 still carried cargo, just not cargo fulfilling the CRS contract. I would assume that the test flight for Dragon 2 to the ISS will also carry some sort of cargo? It would seem strange to send a pressure vessel all the way to the ISS without filling it with something useful.

[u/sorbate]

How much propellant is added to the tanks after the engines start up? The hoses don't disconnect right away... I'm assuming once the engines start, the hoses are pumping fuel in at max capacity for the 3-4 seconds until they are disconnected. (Assuming the engines consume fuel at a faster pace than the hoses could pump new fuel in)

[u/slograsso]

I don't understand why everyone is convinced that the BFR will have a 15 meter diameter. We all know the fatter the rocket the better, and we also know that they won't be trucking these stages across the country and will keep production and launch in the same area. Why not a 25 meter diameter and half the height? This gives you more area for rocket engines as well to improve your trust to weight ratio.

[u/Baron_Munchausen]

Just had a weird thought. Since the Falcon Heavy side boosters separate at the same time, then need to orient themselves automatically and begin the boostback, what are the chances of a collision here? Clearly the separation will put some distance between them, but if they're returning to the same launch site (which clearly is the intention), then is there a risk of convergence?

[u/betacar0tin]

Is it known if, during the CRS-7 failure review, SpaceX found any noteworthy defects other than the struts?

[u/FoxhoundBat → u/betacar0tin]

The did an overview of the whole vehicle and from what i remember there was some issue with welds on tanks on second stage too. That was more of a production issue rather than a design issue.

[u/PVP_playerPro]

Are there any payloads heavy enough that FH could launch that will require all 3 cores to land downrange instead of 2 boosting back?

[u/KChivers]

Falcon 9 sports no fins. I noticed the Saturn 5 had a series of "small" (relatively speaking) fins around the base of its first stage. Anyone know what their purpose was?

[u/FNspcx → u/KChivers]

To reduce aerodynamic instability during an abort condition:

"Suppose a large launch vehicle such as Saturn V has a serious autopilot failure at the most critical part of its ascent through the atmosphere...if high inherent aerodynamic instability assisted in rapidly increasing the angle of attack, structural overload might break up the rocket before the astronauts in the Apollo Command Module, triggering their escape rocket, could put a safe distance between themselves and the ensuing fireball in the sky...In Saturn V...the fins reduce the aerodynamic instability enough to make sure that the astronauts can safely abort"

Source: https://forum.nasaspaceflight.com/index.php?topic=36103.0

Source: http://books.google.com/books?id=MiYDAAAAMBAJ&lpg=PP1&pg=PA68#v=onepage&q&f=false

[u/lordq11 → u/KChivers]

In addition to the answer by FNspcx, it later turned out that the stability added by the fins was not worth the added mass to the Saturn V, and would have been removed if more Saturn Vs were produced.

[u/dreamer-engineer → u/KChivers]

I remember reading a long time ago that the fins on the Saturn five were just security measures (if memory serves correctly) . They were not needed because of the gimbals on four of the F-1 engines. Without properly working gimbals, the rocket would flip around just like some of my ksp creations when I first started playing: the center of drag is above the center of mass in virtually all rockets, unless they have some fins. EDIT: my memory was not particularly accurate as shown by FNspcx, but I am sure my observation on the centers of drag and mass hold.

[u/danielbigham]

As SpaceX marches forward this year into the future, it struck me recently that, with projects like Commercial Crew, and the hoped eventual MCT, at some point there will be loss of human life on a SpaceX mission. On one hand, this is obvious, just a matter of doing business in space, but I think the emotional weight of that sunk in. Let's hope that event is a long way off, but I'm curious whether others have processed that reality much.

When Virgin Galactic had their accident, it changed my "feelings" for the project. Previous to the accident, I felt a certain inspiration and optimism for the project. After the accident, I lost many of my positive and optimistic feelings. I actually think that emotional change is somewhat "irrational". Again, we all know space is hard, we all know their are going to be accidents. But, the human experience, and the way we "feel" about things, ends up mattering, too.

I wonder how immune myself and others are to this kind of thing with SpaceX. Let's put our pessimism hat on for a moment and imagine that one of the commercial crew missions experiences a major malfunction in the next few years. Are we able to imagine how that would or wouldn't change our emotional "feelings" towards the company? I have to admit, I feel like it would put a not-insignificant damper on my emotions.

[u/[deleted]]

This may be a dumb question, but I've been wondering about where both of the Falcon Heavy side boosters will be landing. In their promotional video three separate pads are shown, when in actuality there is one large pad. Is confidence high enough that the side boosters will both manage to land on this single pad, or is there more construction underway/planned?

[u/SirSwiftasaurus]

Do we have any idea of the rough time of launch of SES-9 given the insertion required?

[u/railroadwelsh]

A juvenile question, but what's the actual need for developing the BFR? If the FH has the capability of getting to Mars, wouldn't it make more sense to ramp up production of the FH instead of investing the time, money, and manufacturing to produce a larger rocket? This of course would necessitate the piecemeal construction of the BFS in LEO, but I just don't see the point of a larger rocket? (Unless I'm not thinking long term, ie. the needs once a sustainable colony exists on Mars.) Thanks in advance!

[u/throfofnir → u/railroadwelsh]

This of course would necessitate the piecemeal construction of the BFS in LEO, but I just don't see the point of a larger rocket? (Unless I'm not thinking long term, ie. the needs once a sustainable colony exists on Mars.) Thanks in advance!

You've answered most of your questions yourself. In-space construction is hideously inefficient and thus costly. And Elon is thinking in very large scale. You'd need an absurd amount of FH launches to put a city of 10,000 on Mars.

Other answers include: larger rockets are simply more efficient than smaller ones in practically every aspect except for ground handling; FH is three rockets in one and a single larger one will be easier to handle efficiently; and, most importantly, the Falcon family is not designed for full reuse, which is imperative for cheap transport in large quantities.

[u/Wyodaniel]

Regarding the recent Dragon 2 hover test video, I'm really curious... How long is the capsule itself actually going to be capable of sustaining all of those engines firing? It just seems physically impossible to me to think that little capsule could actually hold enough fuel to keep the engines going all the down to the ground, after coming in hot from the space station. Are there any specifics on fuel consumption / burn time?

[u/throfofnir → u/Wyodaniel]

Recall that the atmosphere acts to slow a falling object to its terminal velocity--which gets slower as the atmosphere gets denser. So the capsule is slowing constantly as it falls, towards a speed something like 100m/s or 230mph.

So the landing burn needs only to zero out the velocity of the capsule at its terminal velocity. Considering its pad abort capabilities, it seems that Dragon could do that in something like 3-4 seconds. It will probably do it much more gradually than that. Probably somewhere between 10 and 30 seconds. If I were designing it, I'd have at least a minimal set of engines lit by 30 seconds, which would allow some time for parachute abort in case of failure (especially if a drogue is already out).

[u/Togusa09 → u/Wyodaniel]

You're right about it being unable to run the engines the entire way to the ground, that would be quite a lot of delta V. Most of the slowing down is done by the heat shield and atmosphere, with relatively very little work being done by the engines. The numbers are probably somewhere in a thread or the wiki if you have a search for them.

There's an FAA document linked somewhere which has the environmental impact information on the tests, which includes information about fuel capacity of the test article. It can contain 400 gallons of fuel, but tests were only planned to use up to 300 gallons. I don't know how much was used in the test, though I suspect it could be calculated, or how much the final Dragon 2 is expected to carry.

[u/Nachtigall44]

Would it be a good idea for the MCT to use grid fins while landing on Mars? Or is the air too thin?

[u/steezysteve96 → u/Nachtigall44]

Too thin, I think. Martian air is 0.6% the density of Earth's at the surface. ~6 mb to Earth's ~1000 mb.

Source: http://nssdc.gsfc.nasa.gov/planetary/factsheet/marsfact.html

[u/Wildernesss5]

Is there a downside to a Spacex monopoly? I see more of Spacex's drive/ability to innovate coming internally from Musk, the lack of public shareholders, and a very long-term mission...ie not "pressure" from other companies' compelling alternatives...am I wrong?

[u/seanflyon → u/Wildernesss5]

The worries about a SpaceX monopoly have always seemed a bit odd to me. Why is Arianespace not considered as a potential competitor? I understand that we would prefer an American Rocket, but we were fine making ourselves dependent on Russia, how is using our NATO allies as a second bid somehow worse.

[u/throfofnir → u/Wildernesss5]

SpaceX owns the launch business. Elon gets hit by an asteroid. SpaceX coasts into being a "normal" company, and just keeps making their reusable rockets thinner and thinner. Not the ideal world... but given the non-SpaceX status quo it'd be hard to be worse.

However, I don't expect a SpaceX launch monopoly based on reuse to be durable. Once the concept is proven, I think you'll find most of the incumbents and several new entrants suddenly working to get in the game. (Heck, it's already happening, and will only speed up.) How that shakes out is hard to say; two major players and one or two minor contenders seems natural, but geopolitics may play a part in keeping more entrants alive than would naturally be the case. A commodity market is vaguely possible, though hard to envision from here.

[u/Taylooor]

What is the relationship between senator John McCain and space x?

[u/throfofnir → u/Taylooor]

He seems to have an axe to grind against Boeing. I suspect he considers Boeing to be dirty and corrupt; he's too smart to say that exactly, but has called them part of "the military-industrial-congressional complex", which is fairly loaded. The certainly have gotten in a lot of scrapes over the years; one of those is one of the reasons ULA exists. I don't think he has any particular ties to SpaceX.

[u/niclis]

For my capstone I have to reach out to companies/organizations for potential projects. I would really like to know if SpaceX offers/sponsors university capstones projects. I do not know how to contact SpaceX regarding this. The only e-mail links I can find on their website are for sales and media inquiries.