If the Shuttle's angle of reentry is too shallow and it skips off the atmosphere, is it lost?

Or does it still have a chance to make it back?

Approximately how far into space would it skip, and what scenarios could cause a too shallow reentry angle?
http://www.space-shuttle.com/abortmain.htm

I can't see it as a free-lunch way of escaping Earth's gravity. It will lose some energy on the too-short retro burn and lose some more on heating before it skips away. The result would be an elliptical orbit that would cause it to soon re-enter the atmosphere. It might not then enter at the right angle for safe entry, or enter at the right place for landing, but it might have another chance to deliver live astronauts, if they can re-establish control.

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Incidentally, I don't think it's a realistic scenario, though someone please correct me if I'm wrong. The atmosphere starts out very thin, and gradually builds up -- it's not like a wall that you hit suddenly. I'm guessing that given the precision of the calculations they do, etc., that this is not something that is even conceivable.

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I don't see how the shuttle could "skip" off the atmosphere. Yes, the atmosphere gets progressively thicker (it's an exponential kind of thing) as one descends into it. At the speed the shuttle is traveling, I don't see how it would do anything but slow as it encounters the ever-thickening atmosphere.

Now that I think about it, I don't think anything truly "skips" off the atmosphere, like a rock on the surface of water. I can see how a meteor (or spacecraft coming from far away) might enter the upper atmosphere at a very shallow angle, maintain enough speed to continue to exceed orbital velocity, and continue out into space with a few less molecules on its surface. Not quite the same thing as "skipping."

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Aerospaceweb.org: Atmosphere & Spacecraft Re-entry

That would be doing small skips deliberately, as a method of re-entry.

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(Emphasis mine)

Forgot about the wings! 8-[ Nevertheless, it does lose speed, and that seems like it would prevent it from being able to escape into space.

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"I am Meteora, supreme goddess of weather" - Meteora, in The Unchained Goddess

One nice thing about being a meteorologist who also likes astronomy is that the sky is always interesting!

Ive always wondered why not just bring more rocket fuel into space, and burn off more velocity during the de-orbit burn. A lot less dependency on heat shielding then.

Somebody answered that question somewhere else, but it has to do with something like: it's expensive to bring up the fuel, and not necessarily safer, because you are now dealing with engines and mechanical issues, etc. It's a waste not to use the atmosphere to slow down spaceships, since it's essentially "free." I think the reentry heating is a pretty well known quantity, so it's pretty safe if things are done correctly -- I don't think there have been any major problems with any of the Soyuz landings, for example. I think it's an issue with the SS because it's so big and is designed to fly once it gets into the atmosphere.

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As above, so below

Saint, why don't you just try it for yourself and see what happens:

http://www.medphys.ucl.ac.uk/~martins/orbit/orbit.html

I think you're over estimating what chemical rockets can achieve. To slow the shuttle down from orbital speed to zero, you would simply need the same rocket stack (SRB's, fully tanked ET) as what got it launched. Which would mean double the weight, someting you could never get of the ground anyway. Now, you don't have to slow it down to zero of course, but this might show that some 100 kilos of extra fuel don't bring you much in braking power.

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I remember that discussion, and I was hoping to find it (I don't know why I have a hard time finding old things here) It was a good discussion.
But basically, it boils down to this. No matter how you slow down (which would take considerable fuel) you still have to consider reentry speed vertically. Eventually you get to a point where the free fall velocity will also need to be accounted for.

As far as skipping? I remember every time an Apollo mission came back from the moon, the press getting all over that concept. They always talked about skipping back into space being a problem. I didn't understand orbital mechanics at the time, and now that I look back, I think the press didn't explain it right. Basically, the craft would just go back into an elliptical orbit that would keep it in space long enough for them to exhaust thier supplies.
Any kind of trajectory that is not above escape velocity will eventually come back around and graze the atmosphere if it was low enough to graze it the first time; therefore, eventually causing a re-entry due to the slowing.

You need more than twice the mass, you need extra fuel to lift the extra fuel!

And if you think for a second, you're never going to GAIN energy by skipping off something, so any atmospheric contact is going to lose some energy. Of course, something like Apollo, coming in at faster than orbital velocity, could easily skip off into space again.

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Yes, I got nervous everytime Apollo came back. The press, the press... :roll:

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I agree. I'm thinking that any trajectory that was already an Earth-orbit would come back around again to intersect the atmosphere. For example, the Shuttle (being in a LEO-like elliptical orbit) would come back around in a matter of a few hours. A lunar return trajectory, however, would take much longer to come back around (around a week?).

It's true that small skips can be used as a method of reentry. That's the topic of my Master's thesis, in progress :-)

Someone correct me if I'm wrong, but I thought that Apollo was never in a "faster than orbital" velocity. It was only in a highly elliptical orbit so that the moons gravity eventually had more influence than the Earths. (and vice versa comming back)
This was the cause of the figure 8 trajectory.

I think the discussion you are thinking of is here: Re-entry Plow

Perhaps a more accurate statement would be 'faster than LEO velocity.' From a LEO, reentry begins at about 7 km/s, whereas a lunar return trajectory is more like 11 km/s. This difference would cause it to take a lot longer to get back around to Earth in the lunar return case, and Apollo astronauts (for example) didn't have an extra week's worth of food and air sitting around in case they had to do another orbit.

Correct. I was imprecise in my statement.

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--Astronaut Glen, "Monster Zero"

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