Advisory Committee Has Issues With Fueling Crewed Falcon 9
Experts concerned by SpaceX plan to fuel rockets with people aboard, Reuters
“It was unanimous … Everybody there, and particularly the people who had experience over the years, said nobody is ever near the pad when they fuel a booster,” [Chair Tom] Stafford said, referring to an earlier briefing the group had about SpaceX’s proposed fueling procedure. SpaceX needs NASA approval of its launch system before it can put astronauts into space. In an email to Reuters sent late Monday, SpaceX said its fueling system and launch processes will be re-evaluated pending the results of the accident investigation.”
OK , You first !
AFAIK the F9 can orbit the dragon and still be recovered without using superchilled densified propellants.
So just use standard chills, gas it up first, and then add the crew.
Would there be a problem with that?
Nope. The current Merlin engines only works with superchilled propellants. The turbo-pumps in the current Merlin engines is not comparable with non-superchilled propellants.
Basically SpaceX have about 30 minutes to launch the current version of the Falcon 9 after propellant loading starts. With a launch scrub if loading is interrupted for any reasons. Seems timing is very tight for the ground close out crew to evacuated the launch pad, if the crew is embarked after propellant loading.
Could you document that?
“The current Merlin engines only works with superchilled propellants.”
The Flacon 9 Full Thrust uses Merlin 1D engines. The Merlin 1D was also used on the earlier Falcon 9 1.1, which did not use superchilled oxygen. There have been some incremental improvements in the Merlin 1D since then, but I’m not aware of anything making it incompatible with “normal” temperature liquid oxygen. In fact, the first think a rocket engine does with cryogenic fluids is to warm them up. So I can’t see how this could be an issue.
Thats what I understood. I would like to see documentation that subcooled LOX is required.
That’s a very sane and common sense suggestion. If the extra margin isn’t needed for the mission, why superchill the props? From everything I’ve read, it’s harder to do, uses more energy (cost) and creates additional failure modes.
Which of these scenarios is most likely survivable by the crew if a major malfunction occurs? A: the crew sitting ready in a Dragon capsule with a launchpad abort facility while the LV is being fueled or B: an unprotected crew approaching and entering a Dragon capsule atop a fully fueled LV? A simplistic view maybe but major problems can happen at any stage of a launch once fueling begins.
Would be safer for the closeout crew also since they wouldn’t be clambering around on a fully fueled rocket.
B for sure. Fueling is the riskiest phase of ground operations. Soyuz crew boards a fueled rocket, too.
F9 doesn’t have a stable period after fuelling starts. Hence the comparison with other systems is false.
That’s what concerns me about the STRB claims. They seem to be fixated on the comparison with other systems, “how things were done before”, rather than looking at the specific vehicle they are being asked to assess.
The safest time for ground support crew to approach the F9 is before fuelling. If you look at the launch timetable, for crew loading to happen after the main fuel loading, that would put it right when the F9 exploded, give or take ten minutes.
NASA Safety Technial Review Board (STRB) assesses the safety risks to the crew and makes the determination for the Commercial Crew Program.
This is a proven process used effectively by NASA for many years to protect the safety of it’s astronauts.
40% of the shuttles failed and killed their crews.
The Captain has the the right to decide to fly or not on an airplane. How about on a rocket. Lets ask the crew. I have never trusted them though. They seem to want to fly too much. I remember one woman astronaut said she was sorry she did not get to ride Ares-1. I agree with her. SRB are the best for Crew. No worries. Nothing to blow up. Maybe the destruct package or the hydraulics. Systems in the capsule, maybe green propellant would be better there. The Pres. could say make it so, though.
“SRB are the best for crew” is an opinion that is not universally held.
Especially by the safety staff.
Ya. Two thrust levels. 1: Cold on the pad, 2: Full burn and can’t stop it. I remember reading an article about that somewhere.
Jeff2Space–
That may win NASA Watch Understatement of the Year 2016.
Engineers have been wary of giant bottle rockets lifting humans into the sky since von Braun.
“Nothing to blow up.” ??? How about the ammonium perchlorate? Other fun issues: Nothing to throttle. Nothing to turn it off.
Even though we have not seen a shuttle SRB case rupture, other large segmented solid rocket boosters have experienced case ruptures. It is a very fast, and very violent event which spews chunks of flaming propellant in every direction. Not something you want to ride on top of.
‘”This is a hazardous operation,” Space Station Advisory Committee Chairman Thomas Stafford’
As compared to actually LIGHTING it and propelling the rocket into space?!?
If you are about to OK a hazardous operation that is an 11 out of 10, then why sweat the hazardous op that is a 8 out of 10?
I would rather be IN the capsule with the LAS during fueling than approaching the rocket on foot once it is fully fueled.
It’s kind of like: “we wont let the Chernobyl reactor cleanup crew approach the core to begin cleaning operations because the Radon detector in the tunnel leading to the reactor building went off once, briefly, last night”
You’ve got a good point, but so does the advisory committee. Even if the risk is small, compared to the overall risk of a launch, it’s just not a good idea to take unnecessary risks. On the other hand, if it is a small risk, and the alternatives are unrealistic or impractical, then there is such a thing as a small, necessary risk.
The simple fact is, as bitter as this fact is to SpaceX, that rocketry technology is nowhere near mature enough to allow for Elon Musk’s dream of airliner-like turn-arounds for spacecraft. That may not happen for a long while.
Yep, we probably won’t see “airliner-like-turnarounds for spacecraft” in our lifetime..or even in this century.
We could see such, but only for the unwillingness of the present generation of decision makers to entertain innovative thinking.
There seems to be an assumption that Elon Musk lives in some fantasy world far from reality but he would not have got where he has if he did, I am sure he fully realizes that Airline like turnarounds for spacecraft are a long, long way off, but by aiming towards that he is inspiring both his staff and himself to achieve the maximum possible. You’re never going to get anywhere if you constantly set your sights low and say well we’ll settle for shaving a couple dollars per pound of the cost of launch to LEO.
That’s because the chosen technologies have performance barely adequate for the job and therefore require designs with razor thin margins, and thus unforgiving. There are other ways.
An airliner-like turn-around takes 15 to 30 minutes. No one, including Mr Musk, is talking about that for rockets. The current ambition is a turn-around time under a few weeks, and eventually decreasing that to a few days. In other words, about a thousand times longer than an aircraft turn-around, with the hope of getting it to only a hundred times longer. That would be a massive improvement in the state of the art, and would result in massive cost reductions.
I have actually asked this exact question at SpaceX and been told the goal is under 24 hours. But I agree, they were pretty hazy about when that goal would be achievable.
I would like to remind everyone who is putting their faith on the astronauts being saved by the abort system of some minor details.
* Abort systems are nasty, nasty things. Now the little information I have found puts the SpaceX abort system at only about 3.8 g’s, which is nowhere near as bad as Orion’s 16 g’s. On the other hand lower g’s means slower escape which exposes the astronauts to danger for a longer period of time.
* To my knowledge NOBODY has ever tested an abort system in an actual emergency situation. Not NASA, not Space X, not Blue Origin. We know the abort systems work nicely when aborting from a stable rocket on the pad or in flight. But what happens when aborting from a fireball?
* There were several cool videos after the Space X explosion that superimposed the Dragon abort test on the fireball to show that Dragon would have gotten away safely. This is true only, and only if, the system detected the anomaly and reacted it to it fast enough. If I recall, Musk said that they only had a few milliseconds of “bad” data before all hell broke loose. Would a few milliseconds be enough for the abort system? Would an autonomous abort system be smart enough to detect “bad” without false negatives? I’m sure Space X is looking at this unexpected wealth of test data (a very small silver lining).
* I’ve always been curious on what might happen to the thrusters in a pusher abort system (e.g. Dragon, New Shepard) as opposed to a puller system (e.g. Apollo, Orion). A pusher system puts my critical escape thrusters that much closer to the exploding rocket. This sets up a perfect race condition between the first bits of junk/exploding gas coming off the rocket and the thrusters trying to get out of the way.
In other words, it is still safer to be away from the vehicle during a fueling explosion than on top of the vehicle relying on the abort system. But this does pose a fundamental problem to the Space X plan to use superchilled propellants.
To my knowledge NOBODY has ever tested an abort system in an actual emergency situation. Not NASA, not Space X, not Blue Origin. We know the abort systems work nicely when aborting from a stable rocket on the pad or in flight. But what happens when aborting from a fireball?
Yes there is a live test of an abort from a failed booster.
Apollo/Little Joe II
https://www.youtube.com/wat…
Such a system was used successfully during a real emergency in the USSR; Soyuz T-10, 1983:
https://youtu.be/mWWDjNTDy_…
Agree with 99 percent of what you say, however I would maintain that fueling with crew already loaded as against fueling beforehand is a case of pros and cons on both sides, yes launch abort systems are not as foolproof as some may think and it is impossible to truly test them in a “real world” situation. However accidents could potentially happen at any stage (although admittedly fueling is one of the riskier stages) and loading crew after fueling has the downside that should a catastrophic failure occur during the period of crew loading there is really no viable escape system for either flight or closeout crew. So loading the crew before fueling is simply swapping a somewhat higher risk situation (with a potential chance of escape) with a somewhat lower risk situation but almost no chance of escape.
I hadn’t considered that. Imagine the AMOS6 event with astronauts and other crew on the gantry. Messy.
I like SpaceX. I’ve been accused (repeatedly) of being a fan-boy. But this business of moving people around near a fueling operation just looks to me like a very dangerous variable multiplier. Even loading the crew first, buttoning it up, and then fueling puts them through an extra stage of risk.
The whole purpose of using super-chilled propellent is to turn the F9 into a GSO com-sat launcher and put SpaceX into that very lucrative business. Once FH is flying, that may not be needed anymore and this extra risk can dropped? Maybe?
I just get annoyed when people condemn Space-X (who have actually helped make Space cool again) as reckless simply because they have analyzed the risks and chosen to do things somewhat differently than say NASA or ULA would, it doesn’t mean they are automatically wrong, they have just come to a different conclusion, I am quite sure every procedure that Space-X has is geared to ensuring the safest possible launches but in a business where a million things could go wrong at any time and leave you with a massive fireball in milliseconds sometimes even the most thorough risk assessment will have a big element of luck attached.
I agree. The most hazardous operation for the crew is crew loading, not fuel loading. The safest place to be from the start of fueling to launch is strapped in with the hatch closed and the LAS armed.
“tested an abort system in an actual emergency situation” is an interesting phrase. Isn’t that the same as actual, operational use of an abort system? If it’s a test, then it isn’t an actual emergency situation.
Another important detail to remember is that the the one and only Dragon abort system full-up test to date was only partially successful. Recall that one of the engines had a performance short fall:
http://spaceflightnow.com/2…
Recall also that even the reduced acceleration rate and flight time of that test would have still saved the astronauts if the Sept failure was of a crew launch instead of a satellite.
Because the Falcon uses no SRBs the rate of propagation and energy of an explosion (even in the case we just saw) is much less than is the case with SRBs, and the lower LAS acceleration is appropriate.
If the failure mode is understood and eliminated than this particular failure will not occur. The launch sequence is a lot more hazardous than fueling, and it is possible (as currently felt by SpaceX) that “the thing they changed” caused the problem, i.e. that the helium expanding into the tank from the manifold dropped below the freezing point of LOX and caused LOX crystals to build up around the tank. These crystals could have severed some of the fibers.
To assure safety it is much more important to do some actual test-to-burst-pressure measurements on the COPVs to assure consistent manufacture, and to reproduce the failure mode, and to continue making unmanned launches with the same vehicle as will be used for human launches.
The idea that it will be safe as long as the fuel is loaded first seems superficial and based on misconceptions and generalities. Since the whole LV will have the same wet-dress-rehearsal and pad hot-fire before each human launch, if the same mode is present the failure will occur during the test.
I appreciate the fact that the Space Station Advisory Committee feels they have to “do something”. But our faith should not be in the abort system or in fueling before boarding, or in redundancy. None of these approaches really achieve reliability. Our faith should be in understanding the actual failure modes and eliminating them at the design level by appropriate changes in design or procedures.
and there is crew escape in Dragon. If that works the rocket could be lost during fueling, but the crew would be safe.
I’m not sure I’m following or even understand Mr. Woodard’s comment. Loading the launch vehicle with fuel is always risky and failure modes cannot be eliminated – they are controlled to reduce the risk.
NASA has always loaded the flight crew into a rocket after loading has been in stable replenish. All the NASA cryo engineer with years of loading experience agree with.
So you load the launch vehicle with densifed propellent, who has extremely limited experience with rockets then load the flight crew is EXTREMELY RISKY!
Take a look at those Falcon 9 explosion videos and when you see that Dragon capsule fall down in the fireball, just think of this being at LC39A with flight crew in the capsule.
Too many Wanna Be Rocket Scientists posting comments.