Capsule Questions

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barrykirk

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I lot of people having been espousing the benefits of<br />a winged re-entry vehicle. One of the biggest benefits<br />listed is the lower max-g's experienced during re-entry.<br /><br />So naturally I have to ask, what is the lowest possible<br />max g's possible with a capsule?<br /><br />And what is the max g force with existing or historical<br />capsule designs?
 
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vt_hokie

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With Soyuz, I think it's like 6 g's nominally and up to 9 or 10 on a ballistic reentry.
 
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nacnud

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That's too high, for a normal decent the Soyuz maxes out at about 3-4g. Only emergency ballistic descents reach up to 8g, there have only been two of those in the entire program.<br /><br />The g-load is eyes in load in special seats which mitigate the effects as much as possible. As a side note 3g are commonly reached in fairground rides.<br />
 
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vt_hokie

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<i> As a side note 3g are commonly reached in fairground rides.</i><br /><br />Kingda Ka at Six Flags in Jackson, NJ subjects riders to 5 g's, from what I've read. That's a fun ride! <img src="/images/icons/smile.gif" />
 
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nacnud

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I suppose i'ts one way to make sure everyones lunch stays down <img src="/images/icons/smile.gif" />
 
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hk8900

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So, what is the max. and average G experienced in a Shuttle?
 
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qso1

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If I remember correctly, its maximum 3 G's on ascent and 1.5 on re-entry. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
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steve82

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"As a side note 3g are commonly reached in fairground rides."<br /><br />As a side note to that side note, there was a story out that Eileen Collins in general avoids amusement park rides and water slides. She was last on Space Mountain 20 years ago.
 
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barrykirk

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I guess I should also add the question of how long<br />does the re-entry stay at max-g's?
 
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barrykirk

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Well, if the shuttle is 3 G's on ascent, then lower G's on<br />descent is nice but not required... For the passengers <br />anyway.<br /><br />I don't think 4 G's is too excessive for the initial space<br />faring public. Initially, I don't think it is beyond reason<br />to assume that people riding rockets should be in good<br />enough physical shape to withstand amusement park<br />rides.<br /><br />Maybe that would be your pre-flight physical. Ride <br />Kingda Ka.... If you don't survive, well than your not fit<br />enough to ride our rocket.<br /><br />As for the cases where the Soyez had emergencies that<br />required 8'gs. What kind of emergencies were those? <br />If a winged re-entry vehicle had those kinds of <br />emergiencies, would it pull 8 g's too?
 
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qso1

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BarryKirk:<br />As for the cases where the Soyez had emergencies that <br />required 8'gs. What kind of emergencies were those? <br />If a winged re-entry vehicle had those kinds of <br />emergiencies, would it pull 8 g's too?<br /><br />Me:<br />There were two Soyuz emergencies in which the capsule was required to sustain excessive G loads. One in 1975, the other in 1982 or 83. Both involved problems requiring the escape tower to pull the craft from the booster and propel craft and crew through 7-8 Gs and clear of the booster.<br /><br />3-4 Gs is probably the maximum that space tourists should be expected to endure and is probably doable with not too much effort. Some of the newer amusement rides are said to be actually scarier than a shuttle launch.<br /><br />A winged vehicle would have to be roughly similar in size to be practical for use of an escape tower but assuming that to be the case, the G load would be about the same in a tower escape emergency. It could be a bit more because the tower would have to get a winged vehicle high enough for a transition to horizontal flight and winged landing. This type of flight mode would minimize possible damage sustained by the winged craft during separation. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>
 
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tap_sa

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<font color="yellow">"As for the cases where the Soyez had emergencies that<br />required 8'gs. What kind of emergencies were those?<br />If a winged re-entry vehicle had those kinds of<br />emergiencies, would it pull 8 g's too?"</font><br /><br />Last time it happened with Soyuz TMA-1 in 2003. The guidance system malfunctioned and as plan B the craft went into lift-cancelling roll and did ballistic reentry.<br /><br />AFAIK winged reentry vehicle without working, active guidance is as good as dead, they are not monostable.<br /><br />Btw the Soyuz launch escape exposes the crew to much higher Gs, somewhere between 15-20. But only for a few seconds.
 
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barrykirk

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I'm going to ignore the cases where the launch tower<br />is used, since a capsule might have a slight advantage<br />over a winged vehicle in those cases.<br /><br />The shuttle has been stated as pulling 1.5 G's max<br />during normal re-entry. Is that normal for most winged<br />re-entry vehicles or would that be considered lower than normal?<br /><br />Again, since normal launch loads of a rocket are going<br />to be 3-4 g's anyway. It seems pointless to require a<br />lower g rating for the re-entry. It might be nice, but it<br />wouldn't be necessary.<br /><br />What would be the lowest possible max g's possible<br />with a capsule assuming everything is working properly?<br /><br />
 
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henryhallam

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I can think of a couple of hypothetical reasons why a lower g-load on reentry than launch might be useful:<br /><br />1. Long-duration missions where the astronauts go up fit and healthy and come down with weak bones<br />2. The g-load can scale up while returning from translunar or interplanetary trajectories but still remain in a tolerable range.<br /><br />Neither of those reasons are particularly compelling or relevant though!
 
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strandedonearth

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Another reason for low g-loads was to make it easier on sick or injured crew members.
 
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nibb31

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"Is that normal for most winged<br />re-entry vehicles or would that be considered lower than normal?"<br /><br />Well, since the shuttle is the only winged re-entry vehicle that has flown, it's hard to draw comparisons.<br /><br />I would tend to think that the G load on re-entry is more a factor of lift surface than wings or not wings. A capsule produces lift too. A freaking big capsule (FBC!) the size of a shuttle would probably have a similarly low re-entry speed. A shuttle the size of a CEV would fall just as fast until it reaches the lower parts of the atmosphere where wings start producing sufficient lift.
 
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rfoshaug

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One should also remember that in the Shuttle, the astronauts sit more or less upright, and the G's they experience is down toward their feet, while in a capsule, the astronauts sit with their backs towards the direction of travel. So their G's point toward their backs and not their feet and it's easier to take more G's for longer perods of time in that direction. <div class="Discussion_UserSignature"> <p><font color="#ff9900">----------------------------------</font></p><p><font color="#ff9900">My minds have many opinions</font></p> </div>
 
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barrykirk

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Didn't Burt Rutan have a solution to that problem. I seem to remember a chair that he was demonstrating <br />that would change it's orientation so that the astronauts back was facing the G-force at all times.
 
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j05h

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The CXV mockup had reversible web-seating that would provide that capability. Not sure if it was a Rutan or other t/space innovator that thought it up. <br /><br />photos:<br />http://www.thespacereview.com/gallery/11<br /><br />josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>
 
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tap_sa

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<font color="yellow">"Not sure if it was a Rutan or other t/space innovator that thought it up. "</font><br /><br />James Voss lead the seat prototyping team. He actually knows thing or two about human spaceflight, ex-NASA astronaut and taught manned spacecraft design at Auburn university.
 
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JonClarke

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The Kliper also has seats that do this.<br /><br />Jon <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>
 
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nacnud

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Not quite like the CXV though, the klipper seats recline/tip back 90° while the CXV seats rotate 180° back to front, the effect is similar though <img src="/images/icons/smile.gif" />
 
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john_316

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I wonder how much it would cost T/Space to actually do the CAD programs and build a test article of their proposed CXV? I am not just talking a mock-up either. I mean to go through with the actual fabrication of the capsule as if were an actual flight vehicle...<br /><br />It would be nice to know how much it would cost in out of pocket expenses for the company to actually build a non-flying model that could be evaluated for future consideration as a Crew Transfer Vehicle to both the ISS and any other LEO station/space vehicle.<br /><br /><br /><br /><img src="/images/icons/smile.gif" /><br /><br />
 
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