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#1800
by
maicod
on 18 Apr, 2009 03:07
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#1801
by
maicod
on 18 Apr, 2009 08:01
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here's a picture showing both the Hubble servicing mission shuttle Atlantis (STS-125) and the emergency backup shuttle for that flight shuttle Endeavour (STS-400) to go with the question on the above 2 replies.
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#1802
by
Spacenick
on 18 Apr, 2009 13:56
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Seems like a rather complex EVA. Why can't they bring all Atlantis crew member sin one go using the entry suits. I know they are not meant for an EVA like that but they should protect enough against vacuum for such an emergency, I mean who cares about MMOD risk in such a situation? Then the crew members with proper EMUs and therfore much higher quality of movement could carry their colleques in the entry suits towards the LON Shuttle.
Or is a use of the entry suits in the real space environment impossible?
What about the rescue balls once imagined? Wouldn't they be ideal for STS-400?
When filt with 1 ATM the rescue balls would also significantly cut the time needed for preparations.
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#1803
by
rdale
on 18 Apr, 2009 14:03
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The entry suits won't work for EVA. The rescue balls don't exist. There's no rush.
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#1804
by
Spacenick
on 18 Apr, 2009 14:09
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I see, it's a pitty they didn't leave the rescue balls ready, I mean they don't look like a very complex system. Is there anything more to them then a space suit material formed into a ball with a small window entry opening and an open system oxygen supply?
I know that the Sokol suits use a simple closure system much like those used for rafting tour bags, So that can't be complicated to do either.
What exactly makes the entry suits incapable of an emergency EVA? Don't they have an oxygen supply, or can't they protect against a hard vacuum. it might be because of the radiation as well.
It's remackable that unlike the US entry suits the Russian sokol suits look quite like they would be feasable as emergency EVA suits.
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#1805
by
ZANL188
on 18 Apr, 2009 16:04
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I see, it's a pitty they didn't leave the rescue balls ready.
What exactly makes the entry suits incapable of an emergency EVA? Don't they have an oxygen supply, or can't they protect against a hard vacuum. it might be because of the radiation as well.
It's remackable that unlike the US entry suits the Russian sokol suits look quite like they would be feasable as emergency EVA suits.
Seems to me the rescue ball would be a pain to get out the hatch..
Although the new LES is considered a full pressure suit, I beleive the footwear is still just a pair of jump boots (like paratroopers wear). An EVA in the LES would be hard on the feet...
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#1806
by
elmarko
on 18 Apr, 2009 17:24
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What's the rationale for shutting down the forward RCS during deorbit and entry? I would have thought that to provide a rotational moment to control attitude you'd still need to fire jets at both ends?
Otherwise you'd be injecting a little +X or -X everytime you fired the aft RCS.
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#1807
by
Lee Jay
on 18 Apr, 2009 17:44
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What's the rationale for shutting down the forward RCS during deorbit and entry?
I don't have a full answer for you, but getting rid of the fuel in the forward RCS helps get the CG in the right location as the spacecraft transitions to an aircraft. If you landed with fuel up there in the nose, you'd need more lead in the aft to get that CG in the right place, and hauling lead to orbit and back is the type of thing you want to minimize if you can.
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#1808
by
elmarko
on 18 Apr, 2009 17:50
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See, I imagined it'd be CG-related, but is that the only reason?
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#1809
by
William Barton
on 18 Apr, 2009 17:51
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What's the rationale for shutting down the forward RCS during deorbit and entry? I would have thought that to provide a rotational moment to control attitude you'd still need to fire jets at both ends?
Otherwise you'd be injecting a little +X or -X everytime you fired the aft RCS.
It's been a long time (decades) since I took a physics class, but I'm under the (probably mistaken) impression you only need to fire one jet off-axis (and pointed opposite direction you want to rotate) to pitch/yaw/roll around an object's CG. You'd only need to compensate with a second jet at the same time (pointing in the same direction as the first jet) for translation.
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#1810
by
elmarko
on 18 Apr, 2009 18:09
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Yes, but if you fired the aft upward facing jets, you'd pitch the craft up, but you'd also inject a little +X into the trajectory, without something on the other end of the ship to compensate.
If I could be bothered I'd draw a hideous MSPaint to demonstrate it
Edit: By upward facing I mean the plume points up. What's the usual nomenclature for this? When you say upward facing do you mean the plume direction?
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#1811
by
Jorge
on 18 Apr, 2009 18:11
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Yes, but if you fired the aft upward facing jets, you'd pitch the craft up, but you'd also inject a little +X into the trajectory, without something on the other end of the ship to compensate.
The effect is negligible compared to the aerodynamic effects.
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#1812
by
elmarko
on 18 Apr, 2009 18:12
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Well, nice to know that I was both correct, but also that it doesn't matter. Thanks Jorge!
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#1813
by
usn_skwerl
on 22 Apr, 2009 05:21
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In an emergency, how many people can fit in one orbiter through reentry? i've heard 11, and i've heard 14. thanks.
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#1814
by
Danny Dot
on 22 Apr, 2009 06:06
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What's the rationale for shutting down the forward RCS during deorbit and entry? I would have thought that to provide a rotational moment to control attitude you'd still need to fire jets at both ends?
Otherwise you'd be injecting a little +X or -X everytime you fired the aft RCS.
The propellant is dumped so it doesn't kill the crew if there is a landing accident. RCS propellant is very toxic. The aft RCS is designed to generate enough rotational moment to control the orbiter.
Danny Deger
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#1815
by
MKremer
on 22 Apr, 2009 08:48
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In an emergency, how many people can fit in one orbiter through reentry? i've heard 11, and i've heard 14. thanks.
10 to 11 with mounted seats. Anything above that and they'd have to string up hammocks or suspended seats in the airlock. (Important to also realize that everyone will need an O2 line and a hardline comm connection.)
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#1816
by
Danny Dot
on 22 Apr, 2009 14:21
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In an emergency, how many people can fit in one orbiter through reentry? i've heard 11, and i've heard 14. thanks.
10 to 11 with mounted seats. Anything above that and they'd have to string up hammocks or suspended seats in the airlock. (Important to also realize that everyone will need an O2 line and a hardline comm connection.)
There is a rumor at NASA an astronaut, I will not name here, did an entry standing up. Keep in mind the shuttle's max G is 1.5 and it maintains a shirt sleeve environment. In an emergency, you could go "standing room only" and all would make it through just fine. Anyone that had been on station for a while would probably need to lie down somewhere.
Danny Deger
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#1817
by
elmarko
on 22 Apr, 2009 15:21
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I thought it was pretty well known that it was Story Musgrave.
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#1818
by
Mach25
on 22 Apr, 2009 20:19
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What's the rationale for shutting down the forward RCS during deorbit and entry? I would have thought that to provide a rotational moment to control attitude you'd still need to fire jets at both ends?
Otherwise you'd be injecting a little +X or -X everytime you fired the aft RCS.
The propellant is dumped so it doesn't kill the crew if there is a landing accident. RCS propellant is very toxic. The aft RCS is designed to generate enough rotational moment to control the orbiter.
Danny Deger
The toxicity concern is more for the ground servicing folks at KSC than for the crew. By dumping it all during entry, they won't have to syphon it out on the ground.
CG management is also a consideration. If the landing CG is going to be a concern, it is likely because it is too far forward. Dumping the forward RCS will shift the CG aft. And if that's not enough, a portion of the OMS (or even aft RCS) propellants can be reserved as ballast to keep the landing CG aft of the forward limit.
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#1819
by
aph
on 24 Apr, 2009 01:22
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I thought it was pretty well known that it was Story Musgrave.
I've been lurking here for a while and have seen others make a reference to this. The question is why did he do an entry standing up?
