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NASA Announces SLS/Orion Flight Slide



 
 
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  #51  
Old May 22nd 17, 12:31 AM posted to sci.space.policy
Jeff Findley[_6_]
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Posts: 1,624
Default NASA Announces SLS/Orion Flight Slide

In article ,
says...

On Thursday, May 18, 2017 at 5:56:37 AM UTC-4, Jeff Findley wrote:
In article ,
says...

trumps presidency will be over really soon....


Off topic.

Jeff


his issues can effect not only our entire country but the entire world. theres now suspicions he is has dimentia.

he could end all human life on our world, by starting a nuclear war........


Still off topic. Keep the non-space related politics out of
sci.space.policy.

Jeff
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  #52  
Old May 22nd 17, 12:44 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Default NASA Announces SLS/Orion Flight Slide

JF Mezei wrote:

On 2017-05-21 14:43, Fred J. McCall wrote:

capsule does, with some minimal lift, gives you 3g or more with jolts
much higher. Note that the Shuttle still restrained occupants in
seats, not just a mattress and some bungee cords.


I never heard about such jolts or hard variations in air density that
would create such jolts.


So you're ignorant. We knew that. How big do you think a density
change needs to be at Mach 25 to ruin your day?


Also, if you are at 3G and then go to 4G for a second and back to 3G,
everything remains "glued" to the floor. Nothing flies all over the place.


You assume all accelerations are in the same direction and normal to
the 'floor'. You assume wrong. Capsules 'wobble' on reentry.


You,d have to suddently go from 3G to 0G and stay there long enough for
gear to start floating, and at 0G, a mere bungee cord would be more than
enough to keep gear on the floor.

At de-orbit burn, floating stuff would fall to the floor, then go back
to floating in 0G until atmosphere starts to generate G forces, at which
point they would fall slowly to floor as G forces increase slowly.

So I really do not unerstand your argument that a nominal re-entry is
violent.


Your lack of understanding doesn't change the facts. You have your
answer. You think you know better. Go sod yourself.


Granted, if the capsule starts tumbling, things will be violent, but
isn't the shape designed to prevent this?


Actually, US capsules are typically biconic, which means they have two
semi-stable attitudes. One is with the heat shield 'down'. The other
is with the nose 'down'. Capsules are NOT perfectly stable on
reentry, which means they 'wobble' on the way down and that will throw
**** inside the capsule around if it isn't properly restrained. If
they ever 'wobble' far enough so that they flip to the other stable
configuration, you're all dead because that end has no heat shield on
it.

In fact, biconic capsules have a certain amount of lift. This means
two things:

1) They actually 'fly' a little bit on the way down, which reduces the
deceleration forces so you only get 3-5 g instead of 9+.

2) Because they actually 'fly' a little bit, down isn't constant.

Now, because there is lift, the decelleration vector isn't straight
through the floor and varies based on angle of attack. Again, a
biconic body is not perfectly stable, so it will also tend to 'wobble'
a bit. But you know better, so why do you bother to ask questions in
the first place?


--
"Ignorance is preferable to error, and he is less remote from the
truth who believes nothing than he who believes what is wrong."
-- Thomas Jefferson
  #53  
Old May 22nd 17, 02:00 AM posted to sci.space.policy
Peter Stickney[_2_]
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Default NASA Announces SLS/Orion Flight Slide

On Sun, 21 May 2017 13:06:01 -0400, JF Mezei wrote:

On 2017-05-21 05:27, Fred J. McCall wrote:


And dies from being sliced to ribbons by bungee cords and jellied
against the sides of the capsule.


Precisely what phase of re-entry would cause that?


Seats. With restraint systems. And shock absorbers. You don't seem
to understand that a capsule reentry can be a fairly violent trip as
such things go.


Which was the goal of my question, but you respond with silly arguments
such as "jellied against the sides of the capsule".




You're talking about peak deceleration of 3g-5g with
random hard jolts in random directions. It's not a nice smooth trip
like you seem to think it is.


Hard jolts? looking at space shuttle re-entry videos, the crew didn't
seem any rougher than on a bus.


Which is the difference between a lifting re-entry by a winged vehicle,
(Well, OK, some other non-winged shapes do perform lifting re-entries
while hypersonic - the Apollo CM, and the Soyuz (Much of the time)
and a ballistic re-entry where your're plummeting out of the sky like a
badly thrown rock.
A shuttle re-entry was typically around 3 Gs. A Soyuz or Apollo, as Fred
says, 5-6. A fully ballistic descent, peak Gs of around 9-12 G,
sustained over a fairly significant period of time (As in multiple 10s of
seconds - when you effectively weigh 2000# (900 Kg), that's damage time.
I've pulled significant Gs in airplanes - good seats, solid structure,
secure (As in a 200 lb crew chief helping haul on the shoulder straps to
get them properly tight) and a G-suit, and you can tolerate High Gs for a
while - _If_ you know that they are coming, what direction they're going
to be, and G onset isn't too sudden.
Rattling around in a jackleg rig is just not going to work.
Think of it this way - one of the biggest killers in airliner crashes has
been seat failure - the relatively low impacts of a crash landing break
the seats away from the structure and impact with bulkheads or the seats
in front of you kills you.

Frankly, you'd be better off with something like MOOSE - (Man Out Of
Space, Easiest) - explored in the early '60s as an "Orbital Parachute" -
A system with a retro-rocket that encapsulates a suited astronaut in an
ablatable capsule, which will, if properly aimed, give you a chance to
use a personal parachute over the right continent.


It isn't like there are flying pigs that get hit by the capsule during
re-entry, is it ?


No, just gravity turns into dense air at high speeds.
You don't need pigs then.

--
Pete Stickney
Struggle no more! I'm here to solve it with ALGORITHMS!
  #54  
Old May 22nd 17, 03:40 AM posted to sci.space.policy
Bob Haller
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Posts: 3,197
Default NASA Announces SLS/Orion Flight Slide

i believe a dragon could safely return one or 2 astronauts safely..

first theres a large lead time, in the event of a soyuz family failure some back up is prudent..

given that today its clear we might need to return astronauts russian or american in a emergency.......

  #55  
Old May 22nd 17, 04:46 AM posted to sci.space.policy
Fred J. McCall[_3_]
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Posts: 9,679
Default NASA Announces SLS/Orion Flight Slide

bob haller wrote:

i believe a dragon could safely return one or 2 astronauts safely..

first theres a large lead time, in the event of a soyuz family failure some back up is prudent..

given that today its clear we might need to return astronauts russian or american in a emergency.......


That's part of what the Commercial Manned Space efforts (SpaceX and
Boeing) are supposed to produce. Meanwhile, a Soyuz family failure
that prevents using them to reenter is unlikely. If said 'failure'
coincides with an ISS failure and you HAVE to get off, you'd use the
Soyuz anyway (after all, whatever might be wrong, they've been used a
lot so the risk is still low). If it doesn't, you've got half a year
to work it out.


--
"Rule Number One for Slayers - Don't die."
-- Buffy, the Vampire Slayer
 




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