Here’s the release from David Thompson in support of the new policy. Orbital was a loser, in that they were the subcontractor to Lockmart’s Orion contract for the Launch Abort System. If Orion isn’t going to carry crew into space (the new plan is for it to be a return vehicle only), then it doesn’t need one. I guess they’re just sucking it up and hoping that they’ll get a lot more cargo delivery business under the new plan.
31 thoughts on “Orbital Is On Board”
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I suspect they’d be happy selling more Taurus II rides. IIRC Orbital is no longer involved in the Orion LAS.
IIRC Orbital is no longer involved in the Orion LAS.
When and how did that happen?
There was some talk that Orbital would want to sell the LAS to commercial crew transport providers.
http://www.spaceflightnow.com/news/n1002/18orionlas/
“The escape rocket that would shoot astronauts to safety from a failing spacecraft in the now-defunct Constellation program could be reborn in future commercial space vehicles, according to the head of Orbital Sciences Corp. “
No one in their right mind would buy it. It’s way overpriced and oversized for any launcher other than Ares I. Also, it’s so complex, I think it would add more hazards than it would mitigate.
http://www.youtube.com/watch?v=vTSDFzKdYVU
Musk has some interesting stuff to say about launch abort in this interview… he really does make “tower” LAS sound like an ugly hack.
How cool. One fuel supply for an integrated system that gives more capability with less weight. Anyone still betting against this guy?
My guess is that orbital has finished most of its LAS development contract, so the only future $$ there is in actual flight hardware….
They are probably smart enough to know there will never be any actual flights so they get $$$ to develop a system that will never be used, hence no risk of embarrassment for tragic failures. Win,Win,Win.
How do you expend your thruster fuel fast enough to be useful as an escape system?
Simply scaling the thrusters up to larger sizes might not handle the needed quick start. Don’t liquid rockets take significant time to get up to max thrust?
The Orbital-Orion LAS is way too large for a commercial taxi spacecraft, by close to a factor of 8-10. Commercial taxi spacecraft will weigh about half of what Orion would have weighed, and require only about 5 G, not 20G, to clear a pure liquid stack. Orion’s LAS is sized to escape an exploding solid.
Orbital will have to start from a clean sheet if they wish to sell a LAS to commercial crew firms.
Orbital is also a member of a separate Northrop Grumman TSER team, with company activities centered at Wallops Flight Facility in Virginia.
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Fred K, how are they going to do it? No idea. But I do know the thrusters on the Dragon use monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO), so start times are very fast. There’s 18 of them fed by 1290 kg of propellant. Some numbers they released over a year ago indicate a maximum thrust of 90 lbf (400N) each, and pictures of the Dragon seem to indicate there will be 10 downward facing thrusters, so yeah, I’m thinking they need to increase that maximum thrust by 20x just to get a G out of them.. doesn’t sound doable. Maybe they’ll have to add more engines.
How do you expend your thruster fuel fast enough to be useful as an escape system?
Bigger pumps?
My impression from the video is that while the fuel is in common, the escape engines are in addition to the thruster engines so I would presume they are capable in that capacity where the thruster engines wouldn’t be. Being on top of the stack is certainly an advantage. I’m wondering what triggers there use? How does reaction time affect things? Is it triggered manually, automatically or both?
Don’t liquid rockets take significant time to get up to max thrust?
I would think the reaction time would be the sum of a few factors. If they can be used all the way up to orbital insertion that’s quite an improvement in safety. It is so cool that they came up with this. I was thinking they would try to show that a traditional escape tower lowers safety and not use one at all.
I wish I’d seen what Trent wrote before my comment. It seems to confirm the impression I got from the video.
IIRC the Soviet Union had plans to use lox/kerosene liquid rockets for braking mounted sideways in Zarya. This was supposed to be a replacement to Soyuz, launched using a Zenit rocket. I imagine the requirements would be similar to those for the Dragon LAS. Zarya was never built however.
“Anyone still betting against this guy?”
Not overall, but I doubt he’ll be able to make that work. First of all, he’s wrong on some details of Apollo LES. It was designed to escape from the pad all the way through Stage II separation, and thereafter the Service Propulsion Engine was the escape engine. Mercury would have used its retros after tower jettison.
The main problem he has is getting a liquid engine that’s big enough to do pad abort, yet will start as fast as it needs to. Solids barely start fast enough. It will need to be a high-pressure engine, pressure fed. The mass fraction will absolutely suck compared to any solid, so it’ll be unnecessarily heavy. And unless he uses a number of smaller engines, firing all of them for abort and fewer of them for orbit insertion, routine orbit insertion will be like an abort — not very pleasant.
I’m not saying it can’t be done, but it will be inferior to a solid (which can also be used for routine orbit insertion, if designed correctly).
Over at NSF.com it was suggested that hybrid propulsion (like that on Dream Chaser) would be ideal for such dual use.
And unless he uses a number of smaller engines, firing all of them for abort and fewer of them for orbit insertion, routine orbit insertion will be like an abort — not very pleasant.
With appropriate injectors, engines can be deeply throttled in vacuum (since there is no problem with underexpansion as there would be with deep throttling in an atmosphere). The Apollo Lunar Module Descent Engine, for example, could be operated at 11% of maximum thrust.
“IIRC Orbital is no longer involved in the Orion LAS.”
“When and how did that happen?”
Last year, around November. “How” was customer direction, though I’m not sure whether it was Lockheed Martin, NASA (MSFC or LaRC), or all three. But the chain of command was just too long, and Lockheed Martin took it over.
I doubt he’ll be able to make that work.
It’s a mass penalty they could probably afford to lose if it doesn’t. Probably best to just not blow up your rocket. 🙂
“With appropriate injectors, engines can be deeply throttled in vacuum (since there is no problem with underexpansion as there would be with deep throttling in an atmosphere).”
Yes, it can be done, but the valve/injector combinations to do it tend to be slow. Even a fast hypergol (and I’ve worked on a few) is far slower than a solid; a throttleable one is slower still.
“Orion’s LAS is sized to escape an exploding solid.”
The thrust-to-weight ratio of the LAS was selected for exactly the same reason that the Apollo LES T/W was: it had to overcome the increased base drag caused by a low pressure between the CM and service module at transonic. Both systems get away at the same rate under that condition.
Elon’s approach is superior in that it would eliminate the low-pressure region imposed by transonic conditions.
Even a fast hypergol (and I’ve worked on a few) is far slower than a solid
What does fast mean in this context? Short ignition delay, high total thrust, something else?
Fast means: getting up to required thrust fast enough after issuance of a “start” command. Fast high-thrust hypergols will have thrust rise rates of ~25,000 lbs-f/sec. A garden-variety solid will do 4,000,000 lbs-f/sec.
Elon could make a liquid abort system with multiple low-thrust engines, because they’d be able to get up to thrust quickly. But the mass penalty would be very high.
“The thrust-to-weight ratio of the LAS was selected for exactly the same reason that the Apollo LES T/W was: it had to overcome the increased base drag caused by a low pressure between the CM and service module at transonic. Both systems get away at the same rate under that condition.”
There is a difference of four to one in acceleration between the two. Base drag is only part of the answer.
Eliminating base drag can done via a gas generator as well and would be a likely superior solution compared with the complexities of a pusher.
“Fast means: getting up to required thrust fast enough after issuance of a “start” command. Fast high-thrust hypergols will have thrust rise rates of ~25,000 lbs-f/sec. A garden-variety solid will do 4,000,000 lbs-f/sec.
Elon could make a liquid abort system with multiple low-thrust engines, because they’d be able to get up to thrust quickly. But the mass penalty would be very high.”
The TRW PAYE demonstrated a thrust rise rate of 1,000,000 lbf-sec.
Ya know, the abort engines on the Dragon could ground start.. There’s some indication that the Dragon’s maneuvering engines are to be used for roll control eventually. The maneuvering engines are already overhanging the second stage, so the abort engines could do the same. As for the mass penalty of multiple low-thrust engines, you don’t have to account for a whole lot of that mass penalty.. it’s dual duty.
Interesting. So they would be low or minimum throttle all the way to orbit, then shut down? How much maneuver fuel might that use?
“There is a difference of four to one in acceleration between the two.”
No there isn’t. Orion weight, 21,000 lb capsule, 13,800 lb LAS = 34,800 lb. Thrust = 508,000 pounds max (right after start of action time). Max acceleration = 14.6 G.
Apollo weight = 12,800 pound capsule, 8,500 LES = 21,300 lb. Max thrust (same condition) = 155,000 pounds. Max acceleration = 7.3 G.
Orion has to overcome 7 G drag at transonic, which sized the motor. Apollo had to overcome 3 G additional drag – and that sized the motor.
So you’re right that the Orion acceleration is higher, but not 4 times. And both were sized by transonic.
The higher acceleration of Orion is due to the worst-case failure mode, case rupture. But it is less due to lethal radius than the reaction time.
I don’t argue with the fact that it’s harder to abort from an Ares than from a liquid of any kind. It’s just not that much harder. The LAS versus pusher trade is still not sorted out, but pushers do offer advantages…
Personally, I think a capsule without escape propulsion provisions is a mistake. But everyone who is doing a capsule (or lifting body) seems to agree.
21,000 lb capsule
Shouldn’t that be: 21mT capsule? Or are you estimating what an ISS-only Orion would weigh?
9,975 kg is the last figure we were given by NASA.
Ah, I forgot that the LAS only has to pull the CM, not the SM and propellant as well.