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A Look At Orion's Launch Abort System
An anonymous reader writes: With the construction of Orion, NASA's new manned spacecraft, comes the creation of a new Launch Abort System — the part of the vehicle that will get future astronauts back to Earth safely if there's a problem at launch. The Planetary Society's Jason Davis describes it: "When Orion reaches the apex of its abort flight, it is allowed to make its 180-degree flip. The capsule of astronauts, who have already realized they will not go to space today, experience a brief moment of weightlessness before the capsule starts falling back to Earth, heat shield down. The jettison motor fires, pulling the LAS away from Orion. ... Orion, meanwhile, sheds its Forward Bay Cover, a ring at the top of the capsule protecting the parachutes. Two drogue chutes deploy, stabilizing the wobbling capsule. The drogues pull out Orion's three main chutes, no doubt eliciting a sigh of relief from the spacecraft's occupants."
In case you didn't have it memorized already.
Yes, that's the way space travel is done...
If you want news from today, you have to come back tomorrow.
Provided, off course, that they hadn't mounted the payload NEXT to the exploding external fuel tank... yes, I know doing it that way let you have lighter structure, but it introduced a whole range of problems and failure modes you wouldn't have had if the orbiter had been mounted on top.
Everything in the world is controlled by a small, evil group to which, unfortunately, no one you know belongs.
I think NASA is in such a hurry to compete with SpaceX that they will cut corners. Coming out with a launch time about similar to SpaceXs' Pray for the astronauts in their capsule. . SpaceX clearly has a place in history despite NASA. Just watch... For SpaceX I wanna ride!
Possibly. Probably not.
The failure modes for the Shuttle are unlike any other spacecraft's - even the near-clone of it, Buran. And any theoretical abort mode for it has to account for that weirdness.
First, the Shuttle has to remain intact. You can't just eject the "pilot area", because the whole thing is really monolithic. You might be able to get away with ejection seats, but that works only for a very small period of spaceflight (probably not Challenger - they'd have ejected into a fireball and coasted up to 60,000ft). They did, in fact, have some ejection seats on the early test flights, with partial crews, but they did away with them in use (letting some escape while leaving others to die was inhumane, and making all seats eject was far too heavy for the marginal benefit).
Second, the boosters cannot be shut off. That's the big safety drawback of solid rockets - you light them, and they aren't going out until they're out of fuel. This means detaching the boosters isn't going to work, because (without the drag and mass of the Shuttle holding them back) they'll just blow past the Shuttle, bathing it in hot exhaust. If my memory is correct, the Shuttle is the only manned rocket in history to use solid engines, in no small part because of this sort of problem. Even the Soviet shuttle clone, Buran, used all-liquid engines.
Third, the Main engines are nearly useless in-atmosphere. They're lit mainly because they sometimes fail to light, and having that failure occur halfway to orbit would suck. The "boosters" provide about 80% of the thrust, if memory serves. The SSMEs aren't even at full throttle for much of the flight - Challenger had just set them to full when the stack exploded. So any idea of "just floor the main engines to outrun the boosters" is ludicrous.
Fourth, these sorts of disasters happen with very little notice. Rocket fuels are generally extremely volatile - even the least exotic combo, LOX+RP1, is still liquid oxygen and high-grade kerosene. LH2 is safer than some things (ClF3 was, and still is, considered for rocket use), but it's still pretty dangerous, and when a tank of LH2 and LOX decides to explode, it's not going to give you even a second's warning. So the escape systems they did add after Challenger probably wouldn't have been usable, because it literally involved jumping out of the Shuttle.
Fifth, the Shuttle is HEAVY. Really goddamn heavy, especially since you're not going to be able to dump the payload during an abort. So you've got the crew, all their supplies, whatever they were carrying to orbit, and all the vehicle mass. Any rocket that could accelerate the Shuttle away from an exploding stack would be itself enormous, not something you could really justify launching into orbit every mission.
Because of these peculiarities, the Shuttle abort modes are along the lines of "pick where to crash" instead of "run away from the explosion". The four post-launch modes are "return to launch site", "trans-atlantic landing", "abort to once-around" and "abort to orbit" - all of which require a mostly-working Shuttle and must be used after the boosters are exhausted.
An LES like this could not have saved them, because you couldn't really use an LES such as this on the Shuttle. Modifying the Shuttle enough that an LES like this makes sense would basically require making it not a Shuttle - in fact, you'd basically end up with an Orion-like capsule on top of an SLS-like stack, because they're literally reusing that much of the technology.
OK, lets rephrase a little, and concentrate on the Challenger failure mode, rather than the actual shuttle.
Imagine a rocket that was compatible with an LES, and also compatible with the Challenger failure mode. (Remove the shuttle, put the liquid fuel engines on the bottom of the external tank, throw a capsule on the top, keep the solid rockets.) Now have the boosters fail in the same way they did with Challenger. Would the LES have sufficient notice to get the capsule to safety?
Quattuor res in hoc mundo sanctae sunt: libri, liberi, libertas et liberalitas.
*sigh* This is one of the biggest pieces of misinformation about solid rockets floating about out there, spread and repeated by shuttle detractors in a cargo cult like fashion until it's now regarded as a law of nature. What most people (including engineers who should know better) don't realize is that you don't need to shut them down in the first place- you just need them to produce net zero thrust. This is done via blowout panels in the front dome, and sometimes by blowing off the nozzle as well. And it's not like this is a new fangled technique either... It was used on the Polaris A-1 and A-2, Poseidon C-3, SUBROC, ASROC, Minuteman I and -II, and Peacekeeper missiles. It would have been used of the SRB's of the Titan IIIC booster for manned Dyna-Soar and MOL launches. It's used by Minuteman III missiles...
It wasn't used by the Shuttle because during the SRB burn, the SRB's are essentially 'dragging' the ET behind it... and thrust termination would have resulted in them 'hanging' from the ET or having to be jettisoned and the resulting changes in structural loads would have shredded the ET and tossed the Orbiter into the airstream where it would be broken up. (Which is essentially what happened to Challenger.) A normal SRB jettison doesn't shred the ET, because the loads come off gradually as SRB thrust decays and they're jettisoned as the T/W ratio passes through 1.
NASA looked at using an Orbiter mounted solid rocket to power it away from the stack, but even if the motor was used on a normal flight for orbital insertion after ET jettison it was too heavy.
A friend of mine, an aerospace engineer by trade, once explained it thusly - "during first stage flight, the SRB's lift the ET and the SSME's lift the orbiter". This isn't entirely true, but it's a useful first approximation. And that being said, other than a brief time right around Max-Q (when the throttles are backed off to control aerodynamic loads) and as MECO approaches (when the throttles are backed off to control G loads) the engines are in fact run at full throttle during powered flight.
Blowing off the top of the motor case is used as standard procedure on the Minuteman II and III to terminate thrust at end of the burn. It's considered precise enough to deliver a hydrogen bomb.
Mounting the orbiter on top has it's drawbacks too... The orbiter's wings now act a lot more like fins, making it harder to maneuver during the early part of the ascent and inducing (very) high structural loads on the stack. And of course the wings are generating lift... right at the part of the stack where they have a nice long lever arm. In addition, if you screw up the stack's angle of attack, you can end up with the wings at an undesirable angle to the apparent wind. (Undesirable in this case means "the wings are trying to turn the vehicle but not the stack", I.E. tearing the vehicle off the top of the stack.)
Isn't Orion a space craft being made by the crooks at Boeing, Lockheed and the other losers who rape the shit out of tax payers, intentionally underbid projects and run decades and billions over budget and laugh at us?
NASA should not be allowed to commission their own spacecraft since the laws currently in place force them to choose contractors like those crooks to build their space craft and when was the last time any of them actually built anything that wasn't a royal heap of shit?
... who have already realized they will not go to space today.. [ http://xkcd.com/1133/ ]
It amazes me how in some circles you don't even need to hint that there was a hint in your speech :)
Because it's solid fueled and thus much more reliable than liquids and, depending on design details, much faster to react. Also, it's pretty easy to build in a passive attitude control system that arcs the capsule out of the booster's path while the Draco will require active differential throttling. (Which in the case of Orion also increases reliability, as the launch abort system doesn't depend on guidance being available.)
Which also means it isn't carried to orbit and poses no further risk to the crew or mission. It also reduces total landed weight, reducing the size of the parachutes required and/or reducing landing shock for the same size parachutes.
Nothing is without risk - and Draco has a number of risks inherent in it's higher parts count and more complex operation that the Orion launch abort system does not have.
There are advantages and disadvantages to both approaches. Neither NASA nor Musk has the absolute One Best Design - because there isn't any such thing. (And both of them are leaps and bounds above the complex horror that is Soyuz's launch abort system. Sure, it worked when called on... but that doesn't change the nature of the beast.)
This came up with Orion in the Ares I design. When solids are breached — either intentionally by range-safety or on-board abort systems, or due to the failure itself — they release a cloud of burning solid fuel debris. With a breach of liquid fuel tanks, such as the shuttle ET, you do get that big pretty fireball, but the actual heat being produced is fairly trivial; so as long as you are beyond the over-pressure wave, you are golden. Burning solid fuel is hot particles, when you pass back through the debris cloud, at the very least your parachute will melt and possibly the capsule itself will be damaged.
(At a more human scale, it's like the difference between getting that whumph of gas fireball from starting your gas griller, versus getting sprayed with burning oil. Accept that solid rocket fuel is more like thermite.)
In order to get far enough away from the solid rocket debris cloud, you need a monster LAS with monster acceleration. That results in a LAS as heavy as the capsule itself. And since Orion is already an over-size, over-weight capsule...
Science is all about firing a drunk pig out of a cannon just to see what happens.
What is old is new again.
If NASA was a programmer she'd be a hack.
I want to do Apollo again.
And yet Boeing is having to hire Blue Turd to develop their next family of large rocket engines for the USAF.
It seems that the much vaunted "experienced" players don't know how to build new rocket engines any more, whereas the non-show vanity project has actually designed and built new generation rocket engines within living memory. (LM is even worse, they have to use surplus Russian engines.) Meanwhile, the first SLS launches will reuse the 25yr old engines off the retired shuttle orbiters; not "engines of the same design", the actual engines pulled off the last three orbiters, burning them up on the first two flights (2017, 2021. No further launches are funded.)
Orion is a poor design, with no mission. The mission it was design for (lunar orbit) is no longer the national goal, and it's completely unsuited to the mission that is the national goal (BEO). It's over-weight, over-priced, and behind schedule.
SLS is a terrible design with no mission beyond its own existence, and is just appallingly overpriced. Boeing is receiving $2.8b for the first two SLS first-stages, in spite of them just being extended shuttle ET's with those recycled SSMEs attached. That's in addition to prior funding Boeing received for designs, reviews, production changes, etc. Just the unit cost. $1.4b each. For just the first stage. This is when NASA projected the SLS launch costs would be $650m per unit for the whole system, including integration and launch ops.
Science is all about firing a drunk pig out of a cannon just to see what happens.
The Orion is totally over designed, too many parts means too many parts to go wrong. A Buran type reusable lander on top of a conventional rocket stack would be simpler and safer. The buran would function as an escape vehicle, get them into orbit or get them back to earth.
Considering how much crap has gone seriously wrong by the time it happens, I'm going to guess you're not getting a 'sigh of relief' when the 'chutes pop...pretty much I'd be saving that until I'm standing outside, on the ground, looking at the bloody thing.
-Styopa
Thanks for your informative post. In addition, there is an issue that I was unaware of until I read it in the original article here: "...Challenger's external fuel tank disintegrated, throwing the orbiter into the local airflow at forces way above design tolerances. It ripped apart, claiming the lives of seven astronauts."
Implying that even if Challenger could have been separated cleanly and undamaged from the exploding tank, it would not have survived. A stronger, and therefore heavier or smaller orbiter, does not seem to be feasible, given the extent to which the shuttle design was already stretching the envelope.
That's why we are back to capsules, I guess.
Am I the only one who had a "holy crap" moment when I saw a headline about an Orion spacecraft?
This is what Orion means to me.
I am now better informed, and I thank you for it.
*sigh* This is one of the biggest pieces of misinformation about solid rockets floating about out there, spread and repeated by shuttle detractors in a cargo cult like fashion until it's now regarded as a law of nature. What most people (including engineers who should know better) don't realize is that you don't need to shut them down in the first place- you just need them to produce net zero thrust.
For "misinformation" it is quite correct, the booster is still burning even if it is producing net zero thrust. For example, if there is premature ignition of a solid rocket booster on the launch pad, then that SRBs will burn out no matter what you do with it, even if it is producing net zero thrust. And a launch pad isn't designed to hold a burning booster for several minutes even if it isn't producing net thrust.
I'm sure that NASA has thought this risk through entirely, but it is still there. The problem doesn't go away just because there is a means to make the booster produce no net thrust.
was the first "all-the-way-down" human decision turtle: 15% higher cost for one-piece SRBs instead of the 4-piece propellant sections.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
You basically described Orion on top of SLS. SLS takes the Shuttle launch system, scales it up a bit (adds another fuel "segment" to the boosters, and a fourth SSME), and puts it into a regular stack.
This would probably have saved the Challenger crew. The scariest thing about Challenger is that the crew actually did survive the explosion - they died when they hit the water, possibly unconscious from the lack of air pressure at altitude. The crew compartment also remained mostly-intact.
In a similar failure on SLS, it's likely the capsule would also have survived. Even if LES doesn't get them away from the explosion, they could probably survive the fireball (particularly since they're now above it, rather than beside it). The parachutes can then bring them down safely.
In an emergency like this, the LES might be triggered by computer. In that case, the LES would be able to safely pull them away from the explosion. If it relies on crew or ground-control to abort, it would need someone that can instantly tell the problem is dire enough to abort.
At least it's not the Rube Goldberg design of MLAS...
https://www.youtube.com/watch?...
But I still agree with others, the NASA designs are over engineered, designed by committee for maximum vendor usage so jobs get created in as many states as possible, making it difficult for Congress to cut their budget.
I remember reading about the development of this escape system a few years back, and as I recall, there was much discussion of the fact that, because of how big a bomb the boost stage becomes if it fails, that the acceleration required to get the capsule off the stack fast enough to avoid being incinerated would be enough acceleration to kill the crew outright. At that time, the escape system was actually even more over complicated, with something like 9 parachutes in 3 deployments involved, so this is obviously an improvement, but I'm still curious about the other part of the problem.
I've decided to Diversify my Holdings. I've divided my cash between my left and right pockets, instead of all in one.
If only the decision was that simple... Sadly, it wasn't.
First there were performance issues; The solid motors need to match to within 5% of each other - which proved essentially impossible to achieve with a monolithic grain as the propellant tended to stratify during the extended pour and the extended curing time. The solid motors needed to have consistent and predictable performance during the burn - which was almost impossible to achieve due to the aforementioned stratification problems. Both problems were also made worse because they couldn't figure out how to safely mix and pour the grains for both boosters in a single batch. Segmented grains, which could be poured in LH and RH segments from a single (smaller) batch suffered from none of these problems.
Next, there's storage and handling problems. The larger the grain, the heavier it is, and the harder it is to prevent it from flowing and deforming under it's own weight. Equally, since the large grains have to be cast upside down they have to be rotated rightside up - and nobody knew how to do that with large monolithic grains. A flex of as little as a couple of millimeters could crack the grain or lead to delamination. Also, segments could be stored individually, reducing fire and explosion risk.
Inspecting the grains with the technology of the time was also several orders of magnitude harder for a large monolithic grain.
Lastly, while there was a only a limited base of flight experience with large segmented grains (via the Titan IIIC)... there was no flight experience with large monolithic grains.
tl;dr version - there were a lot fewer known unknowns with segmented solids than with monolithic solids. A number of the known unknowns for monolithic grains were either outright show stoppers or could result in ruinously expensive R&D programs to discover if a solution was even possible. The known unknowns for segmented grains were all issues of scaling from existing experience.
No. There was no way this kind of system could have been installed on Challenger, the designs are incompatible.
Some kind of parachute system on the inner crew cabin might have saved the astronauts (since the crew cabin apparently remained more-or-less intact until it hit the water), but without some kind of additional ejection system on the whole cabin, parachutes would only have been useful if the Shuttle disintegrated in flight. Sure, it turned out that that's what happened, but can you imagine anyone trying to get that through a design review?
The real problem is the idea of combining humans and cargo. They really need to be on separate flights. The shuttle should never have happened. Likewise, orion on the SLS with mission cargo will be a disaster in the making.
I prefer the "u" in honour as it seems to be missing these days.
Accept that solid rocket fuel is more like thermite.
Yes, do accept that.
Science is all about firing a drunk pig out of a cannon just to see what happens.
*sigh* This is one of the biggest pieces of misinformation about solid rockets floating about out there, spread and repeated by shuttle detractors in a cargo cult like fashion until it's now regarded as a law of nature. What most people (including engineers who should know better) don't realize is that you don't need to shut them down in the first place- you just need them to produce net zero thrust. This is done via blowout panels in the front dome, and sometimes by blowing off the nozzle as well. And it's not like this is a new fangled technique either...
Actually, you can do even better!
It has been known for many decades that you can quench a burning propellant by subjecting it to a rapid pressure decrease. (The conductive flame structure cannot rapidly adapt the the decrease pressure and goes out.) Thus, blowout panels could actually be designed to quench the solid boosters. And this knowledge existed when the shuttle was designed.
But there is a finite price on human life and, like the ejection seats or parachutes on the shuttle or passenger airplanes, losing a few dozen astronauts is cheaper than accommodating safety systems.
We make it seem like it would be impossible to have these safety systems, but it isn't impossible. It would just be less efficient for the company or government... who only really cares how much your death costs them.
We know who has cut corners and killed our astronauts so far right? Need Another Seven Astronauts. You are short of memory. SpaceX is cutting costs no doubt. Just like America needs, to compete.