Escape Systems for Unmanned Spacecraft

[rodion_herrera]

Correct me if I'm wrong but, there seems to be no existing escape systems for unmanned spacecraft. Why? Is it a cost issue? Just curious. Just thinking about the loss of the Cygnus onboard the Antares.

[Nibb31]

Cygnus weighs something like 5 tons, including 2 tons of underwear, groceries, and science experiments. A launch escape system for something like Cygnus would weigh well over 2 tons, meaning that you would save the Cygnus, but it wouldn't be carrying any payload. Even if it did have an escape rocket, Cygnus isn't designed to land intact, so it would be destroyed by the splashdown or land impact.

If you really wanted to save it, you would need a much larger rocket, parachutes, and some sort of landing device, but then you go against the whole point of having a small cheap cargo launcher. It would also be more complex, and introduce more risk of failure: what if your LES fails to separate, or blows up the rocket?

Supplies are cheap and experiments can be rebuilt. Expensive stuff is insured. It really is no big deal.

Edited October 30, 2014 by Nibb31

[shynung]

What needs to escape? There's no one inside the spacecraft, so no one dies of the rocket go boom. Launch escape systems are designed to save human lives on manned spacecrafts.

One manned spacecraft that interestingly has no LES is the Space Shuttle. The crew can't do much if one of the main engines suddenly quit.

[rodion_herrera]

I didn't realize the weight issues involved. Still, one day, I think even without human beings inside, there will be a need for "escape" systems for unmanned spacecraft. For instance, what if there are entities like "robonauts" in them? What if such entities are really expensive and costly to remake? What if said entities have gone sentient? Still adapt the "disposable" mentality?

[shynung]

what if there are entities like "robonauts" in them? What if such entities are really expensive and costly to remake? What if said entities have gone sentient? Still adapt the "disposable" mentality?

If it's costly, get insurance. If it's sentient, backup the programs into another chassis, so that losing the original in a great ball of fire has little effect to the entity.

Really, LES is for irreplaceable payloads, like human astronauts (you can't copy human memories and personalities into another body. At least not yet). If humans themselves can be copied in relative ease, LES would be obsolete.

Edited November 3, 2014 by shynung

[Nibb31]

I didn't realize the weight issues involved. Still, one day, I think even without human beings inside, there will be a need for "escape" systems for unmanned spacecraft. For instance, what if there are entities like "robonauts" in them? What if such entities are really expensive and costly to remake? What if said entities have gone sentient? Still adapt the "disposable" mentality?

If it's as valuable as a human, then stick it on a human-rated spacecraft. The whole point of a robot, like any other hardware, is that it's expendable and can be rebuilt if necessary. You only lose money, but that's what insurance is for.

But we're not there yet. It's better to use a cheap launcher to launch cheap stuff.

[rodion_herrera]

My point is, if they can make something like Dragon 2 with the thrusters and no-parachute, pinpoint landing, perhaps one day something like that can be applied to unmanned spacecraft as well. Rocket engine explosion detected, detach, hover, and find a safe spot to land.

[Capt. Hunt]

What needs to escape? There's no one inside the spacecraft, so no one dies of the rocket go boom. Launch escape systems are designed to save human lives on manned spacecrafts.

One manned spacecraft that interestingly has no LES is the Space Shuttle. The crew can't do much if one of the main engines suddenly quit.

Well, that's because an LES on the space shuttle would have added too much weight, cutting down on the amount of payload capacity, also there was some question as to whether or not it would have worked. Columbia was originally built with ejection seats, but the STS-1 crew went on record saying that they would have been ejected right into the exhaust from the SRBs had they used them. Even without the ejection seats installed, the remaining hardware and structural enhancements required for them made Columbia too heavy to safely rendezvous with Mir or ISS. They also investigated a separating cockpit capsule after Challenger, as the cockpit did survive the explosion, but the added weight of structural reinforcements, separation rockets, explosive bolts, parachutes and rescue equipment would have negated the effectiveness of such a system, not to mention the modifications potentially posing their own hazards and the added cost of retrofitting the remaining shuttle fleet. NASA did come up with a variety of abort scenarios, it wouldn't have been entirely hopeless for the crew.

[rodion_herrera]

Again, what about a system like the Dragon 2's? Too expensive, and can't deal with more weight?

[Capt. Hunt]

Realistically, a powered landing abort would be unlikely, even for Dragon 2. It's too complex of a system. if something's gone wrong, you'd have no way of knowing the superdraco's are going to work properly. You just go with the quickest, safest and simplest way to get the capsule back to the ground. That's why Dragon has backup parachutes.

In any case, you have to spend money and weight on whatever recovery system you need, why do that when your fancy satellite was insured.

Edited October 30, 2014 by Capt. Hunt

[rodion_herrera]

Realistically, a powered landing abort would be unlikely, even for Dragon 2. It's too complex of a system. if something's gone wrong, you'd have no way of knowing the superdraco's are going to work properly. You just go with the quickest, safest and simplest way to get the capsule back to the ground. That's why Dragon has backup parachutes.

In any case, you have to spend weight on whatever recovery system you need, why do that when your fancy satellite was insured.

I wish someone from SpaceX can counter that

[Streetwind]

There's no real technical issues preventing that. The practical issue preventing it is that you need to pay money to carry the launch abort system to orbit on every launch that doesn't fail. It has a mass, and mass is subject to the cost per kg to orbit (and that's not counting development, maintenance and testing of these systems).

Ultimately, it's probably cheaper to lose one out of 20 payloads than to launch 19 unused launch abort systems. The more reliable your rocket gets, the worse your balance is going to look. And if no human lives are involved, you're probably going to opt for the cheaper route.

Of course, if the cost of launch comes down by a factor of 10 or more, as SpaceX is planning to achieve, then it suddenly might make sense because the payload becomes the dominant cost factor. Who knows? We'll just have to see what the future brings.

Edited October 30, 2014 by Streetwind

[Nibb31]

Again, what about a system like the Dragon 2's? Too expensive, and can't deal with more weight?

Dragon 2 has Super Draco thrusters that can be used EITHER as a powered landing system OR a launch abort system. Aborts will always be over the ocean, so in case of a launch abort it splashes down with parachutes because it no longer has enough propellant to ensure a powered splashdown. A powered splashdown is useless anyway, because history has shown that a parachute splashdown is perfectly survivable, compared to a parachute landing, which needs something to cushion the landing (airbags or rockets).

If you want it to do both abort and powered splashdown, then it has to carry roughly twice as much propellant, which means less cargo on each flight for no proper reason.

The SD engines on Dragon 2 are justified only because the same system serves two purposes. Remove the LAS requirement and powered landing becomes a superfluous luxury that eats into your payload. Remove the powered landing and you are better off jettisonning the LAS as soon as you no longer need. If Dragon 2 was unmanned, you would need neither, thus Dragon 1 still exists for cargo because it can carry more payload.

But again, cargo is cheap, most of it is groceries and fresh clothes, so there really is no point in spending huge amounts of money on preserving it.

Edited October 30, 2014 by Nibb31

[peadar1987]

"Stage and wiggle boys, stage and wiggle"

[lincourtl]

If it's sentient, backup the programs into another chassis, so that losing the original in a great ball of fire has little effect to the entity.

Your unseen robot overlords note your callous disregard for non-meat-based life.

[magnemoe]

Realistically, a powered landing abort would be unlikely, even for Dragon 2. It's too complex of a system. if something's gone wrong, you'd have no way of knowing the superdraco's are going to work properly. You just go with the quickest, safest and simplest way to get the capsule back to the ground. That's why Dragon has backup parachutes.

In any case, you have to spend money and weight on whatever recovery system you need, why do that when your fancy satellite was insured.

It will also use the superdraco for the separation during about and will not be able to use it for landing without parachutes.

Yes if Dragon2 is used for unnmanned missions they will probably do the abort to save it for reuse.

The cargo in it can also be reused but would probably be less expensive than the pod.

[Kryten]

Reusing dragon requires a market for reused dragons. Right now there isn't one.

[Guest]

First, developing something complex almost always way more costly process then building it. So just insure it, and you will get money to rebuild it.

Second, imagine some piece of complex scientific equipment survived launcher failure, abort system firing, violent shaking in the air, and badly cushioned landing. Will you still trust it? It's cheaper to make another one then to refurbish old one.

[Sky_walker]

Second, imagine some piece of complex scientific equipment survived launcher failure, abort system firing, violent shaking in the air, and badly cushioned landing. Will you still trust it? It's cheaper to make another one then to refurbish old one.

That's why capsules have accelerometers. So you would know if your equipment went over it's G-force limits or no, and you wouldn't rely on blind "trust" but rather made an informed decision.

[sp1989]

Again, what about a system like the Dragon 2's? Too expensive, and can't deal with more weight?

Thats a ship that is designed to return. The cygnus burns up in the atmosphere like the progress. So the discussion is to put a LES on a ship that that in no way shape or form is designed to be reused. Now it is a shame the rocket exploded and the cargo was lost. But everything can be replaced. Rockets explode, the whole idea of rocketry is controlling an explosion to propel you where you want to go. The only thing we can hope for is that explosions and accidents don't happen in manned flights and prepare for accidents if they do occur. In this case the rocket from top to bottom was expendable. Every part of it was expendable. So yes its unfortunate that the cargo wasn't delivered but the end result is ultimately the same. With the exception of the launch pad being damaged, which is probably far worse of a problem then the rocket being destroyed.

[rodion_herrera]

Thanks for all the input, really helped me understand the situation.