Advanced Question ACES Bailout in a Capsule

[Astro SG Wise]

Hey, I was just looking at some sweet pictures of the Advanced Crew Escape System "pumpkin" suits, and I was wondering of some future designs, mainly for the Orion MPCV. The Orion mockups, conception designs, and images all have the crew in ACES suits. The shuttle, obviously much different in design, had the suits for bailout, and bailout was in the event of a failed launch. In a capsule, like Orion, the LAS would take care of abort from the rocket, but if the parachutes did not deploy, the crew would have to bailout. If one was falling from the sky in a capsule, how would he get out of his super metal re-enforced seat and out of the spacecraft in time before they hit the ground? Even worse, what about bailout in a re-entry? Going at 26 Mach, it would be nearly impossible to jump out, wouldn't it? The ground would be rushing up to them fast.

I sure hope that ejection is possible, mainly because bailout with those sweet orange suits would be legendary! Anyone commenting with more experience/knowledge than me (or less) would be greatly appreciated.

 

[Andy44]

Ejection seats are bulky, heavy and dangerous, so there won't be any. Generally, the seats in capsules are not "super-reinforced metal", but pretty flimsy jobs that can be folded up and stowed for freefall operations to make more room inside during the mission. They are designed to take stresses in a limited range of directions in order to provide some protection for the crew in a hard landing, and even then they are of limited use. Apollo astronauts expected to be injured in the event the capsule came down on solid ground instead of water.

 

[Star Voyager]

I remember John Glenn saying that he was offered a parachute for MA-6, but he refused because it wouldn't have done him much good.

 

[Andy44]

Well, Yuri Gagarin used one...not sure how it compares in any way.

 

[Hlynkacg]

Well, Yuri Gagarin used one...not sure how it compares in any way.

Not really comparable as in his case the ejection was actually part of the planned re-entry profile. The early Vostok spacecraft were never designed or expected to land safely. As such it was SOP to jettison any vital equipment (including the cosmonaut) prior to impact.

I am assuming that your capsule has it's own chutes yes?

Those chutes are (unlike Vostok's) disigned to slow the capsule to a non-lethal velocity yes?

If so why would you bail out?

 

[orbitingpluto]

The line of reasoning from "Shuttle had crews suited up in ACES in case they needed to bailout" to "Orion has been shown with ACES used by crews- ergo crews will need to bailout from Orion" misses a few other facets about ACES, like how it was also made to protect astronauts from more than just jumping out of a Shuttle. The ACES was the thing keeping an astronaut alive when a incident happened where they didn't die immediately but the spacecraft around them wasn't shirtsleeves-friendly anymore. That includes keeping them breathing at altitudes too high to bailout at, protecting them during cabin fires, and in addition safeguarding them during bailouts, and in the water should they have to bailout into the drink.

Anyway, per the Shuttle Crew Operations Manual and the Crew Escape Workbook, bailouts on the Shuttle would take place somewhere at or below 30,000 ft, and the Shuttle would be subsonic. According to the SCOM, bailing out 8 persons would take two minutes, and the Shuttle would (hopefully) be on autopilot holding a steady glide. You should take note of the fact bailouts would be called for in situations where the Shuttle couldn't land as normal on a runway, like if part needed to land failed or if they couldn't reach a landing site.

So, how about Orion? Well, unlike the Shuttle, Orion is built to land in the water, and could conceivably smack into the ground in such a way as to be survivable for the crew inside, so bailing out would have to be a very special case like a total failure of every chute onboard. If that did happen, I'm unsure if they would have enough time to do much. As for jumping out at mach 26, that's near orbital speeds; ACES or not, that astronaut dead, and likely bought the farm as soon as he opened the hatch.

I remember John Glenn saying that he was offered a parachute for MA-6, but he refused because it wouldn't have done him much good.

Well, Yuri Gagarin used one...not sure how it compares in any way.

Yuri's Vostok was built to eject him out, allowing him to parachute to the ground as expected way to land, while Glenn was strapped into a much smaller capsule and expected to stay in the capsule for landing. If Glenn wasn't thinking of how unlikely it would be for him to get of of the capsule and still have time to parachute safely in case something went wrong, he might have been thinking of of how a bulky chute would have made his Mercury even more cramped.

 

[Urwumpe]

For a capsule, it is better to stay on-board. Simply because when it falls, you will have no chance to bail-out safely. Also, a backup chute for capsule and all astronauts weights less than individual parachutes for the crew.

 

[Astro SG Wise]

I am assuming that your capsule has it's own chutes yes?

Those chutes are (unlike Vostok's) disigned to slow the capsule to a non-lethal velocity yes?

If so why would you bail out?

Yes, it has chutes, but the problem would be if the parachutes did not deploy. Of course, not only does Orion have mains, but also drogue. Let's say drouge chutes operate, but then the mains fail. What now? A smashing landing. The point of wearing a parachute is if the parachutes fail on the vehicle.

Orbiting Pluto, thank you for the clear up. Yes, it would make sense to stay in the capsule, because at a free fall, where your spacecraft can't glide, your going to hit the ground pretty soon anyway. I understand that the ACES are used for more than bailout, but also, they are called Advanced Crew Escape Systems, aren't they :lol:? Either way, the deal was if it would be possible if the crew could climb all the way to the hatch in the case of parachutes failing to deploy.

 

[Urwumpe]

Let's say drouge chutes operate, but then the mains fail.

What is the chance of all three main parachutes failing? Or at least two of them? Is this risk higher than the risks of attempting to bail out of a tumbling, falling capsule?

Remember: A capsule is no space shuttle. A shuttle can glide in a controlled attitude. A capsule only has stable aerodynamics at high mach numbers. At low supersonic or subsonic speeds, it is as stable as a falling toast.

 

[Hlynkacg]

Yes, it has chutes, but the problem would be if the parachutes did not deploy.

Sure, but engineering wise it is both cheaper and safer to add a back-up chute to the capsule itself than it is to issue individual chutes to the astronauts and have them attempt to bail out of a tumbling capsule.

 

[Astro SG Wise]

What is the chance of all three main parachutes failing? Or at least two of them? Is this risk higher than the risks of attempting to bail out of a tumbling, falling capsule?

:embarrassed: Oops, duh. I was thinking of all of them being pushed out by the same mechanism. If one of them failed, it would be safer, good point. One question though, if the drogue cover does not deploy, none of the chutes can, right? They are all held under the cover.

 

[Andy44]

The irony here is that a capsule system has been used in several aircraft in lieu of individual parachutes. The idea is that a supersonic bailout is more survivable if the crew stays inside a capsule. In fact, had the space shuttle been able to incorporate a robust bailout option for the crew it likely would've been s system such as that.

So, for something that flies out of space at hypersonic speeds, the same principle would apply. Stay in your capsule and trust the engineers and chute riggers to keep you safe.

 

[Urwumpe]

:embarrassed: Oops, duh. I was thinking of all of them being pushed out by the same mechanism. If one of them failed, it would be safer, good point. One question though, if the drogue cover does not deploy, none of the chutes can, right? They are all held under the cover.

The thing is: You NEVER have just one deployment mechanism for such things. You have at least three independent. Or, if you have three independent systems, for example also two independent igniters for the pyrotechnics.

The chance that everything fails is never null, but then, you can reduce the chance a lot that it fails:

Lets say, you have an unrealistic 50% chance that one igniter one of the deployment mechanisms fails.

You have three pyrotechnics to push the drogue cover away. One alone is enough to release the drogue cover.

So, lets do probability calculations: The chance of one pyrotechnic not igniting by both igniters is 0.5 * 0.5 = 0.25 - you can say, in 25% of all landings, at least one pyrotechnic will fail.

The chance of all three pyrotechnics not firing is 0.25 * 0.25 * 0.25 = 0.015625 - you have suddenly just a 1.56% chance that the drogue cover will not be released and your landing will fail because of it. And that despite your igniters having just a 50% chance to succeed.

And such calculations can be done for every component and every subsystem and every sequence - its part of normal systems engineering for any spacecraft. In reality, you will have a 99.95% chance that an igniter will work, failures are mostly by manufacture problems.

 

[Astro SG Wise]

Good points all. Yeah, that makes sense. I had been puzzling over this problem for a while, with bailout right after re-entry, and it seemed almost impossible. I would trust the parachutes, but, as always, just to be safe! I mean, by the time you would make it to the hatch, you would be dead anyway, especially if you look at it from this angle.

Also, because one is going at such high speeds, would he or she have a problem with spinning backwards at such high altitudes if assuming the spread eagle stance?

 

[dman]

Soyuz uses set of solid fuel retro rockets designed to fire 1 M (3 1/2 ft) above ground to cushion the landing impact

The main parachutes slow to the descent capsule to 24 ft/sec (16 mph) which is too fast
for a safe comfortable landing

 

[Astro SG Wise]

Sure, but engineering wise it is both cheaper and safer to add a back-up chute to the capsule itself than it is to issue individual chutes to the astronauts and have them attempt to bail out of a tumbling capsule.

Right, but actually, Orion's RCS systems can keep it at a heads up position quite well, it wouldn't actually be tumbling.

 

[Andy44]

Right, but actually, Orion's RCS systems can keep it at a heads up position quite well, it wouldn't actually be tumbling.

So now you have to possibly jump out through a hypergolic jet plume in addition to hurtling™* through the sky at supesonic speeds...I'd rather trust the redundant chute pyrotechnics.


*word of the year!

 

[Thunder Chicken]

If one or more of the three canopies were to fail to open on the capsule, the velocity increase would not be proportional because drag is proportional to velocity squared.

Assuming something similar to the Apollo splashdown speed of 32 ft/s for all three canopies:

If one canopy failed, the velocity would be sqrt(3/2) ~ 1.22 times the velocity if all three canopies opened properly, or 39 ft/s.

If two canopies failed, the velocity would be sqrt(3/1) ~ 1.73 times the velocity if all three canopies opened properly, or 55 ft/s.

This is first-order simplistic as it neglects the drag on the capsule itself and the canopies actually influence the drag on each other, and even a streaming partially or fully collapsed canopy can provide a lot of drag. The point is that even if the deployment is less than nominal, there is still a good chance of a hard but very survivable landing.

---------- Post added at 09:32 PM ---------- Previous post was at 09:29 PM ----------

Actually, here is a graphic that indicates the touchdown speeds for Apollo - 32 ft/s for all three canopies, 36 ft/s for two canopies.

---------- Post added at 09:42 PM ---------- Previous post was at 09:32 PM ----------

...hurtling™*

*word of the year!

It sounds like a great sport for the Olympics.

 

[Astro SG Wise]

So now you have to possibly jump out through a hypergolic jet plume in addition to hurtling™* through the sky at supesonic speeds...I'd rather trust the redundant chute pyrotechnics.

Well yeah, JUST A NOTE: I WANT THE PARACHUTES TO WORK! :rofl:.BUT, just in the case of an emergency, I would want all the options I could get! For the "hypergolic jet plume", it would only be for about half a second.

Now, at the speeds of re-entry, would the ACES parachutes rip?

 

[Urwumpe]

Well yeah, JUST A NOTE: I WANT THE PARACHUTES TO WORK! :rofl:.BUT, just in the case of an emergency, I would want all the options I could get! For the "hypergolic jet plume", it would only be for about half a second.

No, for much longer - the unburnt fuel/oxidizer of the onset/shutdown of the thruster firing would simply blow into the capsule with the exhaust of the thruster firing, once the capsule is open. Luckily, the astronaut already wears a pressure suit. sadly, you would need to decontaminate the astronaut before he could take off his ACES suit.


Also, you overestimate the thrust of the RCS there. The thrusters are designed for space and upper atmosphere and will loose a lot of thrust to ambient pressure. The capsule would still be tumbling a bit while the thrusters are busy preventing much worse - for a few seconds before running out of fuel.

Now, at the speeds of re-entry, would the ACES parachutes rip?

No, the astronaut would be cremated long before he could pull the release handle.

You can say, as coarse rule of thumb: Deploying a personal parachute at any speed above Mach 0.5 is nearly impossible, above Mach 0.3 it is risky.

For any high speed egress, you have special stabilization systems that have only the job of bringing you into the range for a successful parachute deployment and use powerful pyrotechnical deployment systems (parachute mortars), that can deploy a parachute even at higher speeds.

But such parachute mortars are not possible in an ACES suit, for a good reason - just imagine accidentally firing one inside the capsule.