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How to Land the Space Shuttle


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1 hour ago, SpaceEnthusiast23 said:

This can also help with ksp if your playing in rss/ro and you're trying to land a shuttle.

As an RSS/RO player, i can confirm this is indeed very usefull! I thought i knew everything but apparently not. Thanks for sharing!

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Didn't know that what they mean by s-turns are actually necessary for all descent. I think many of us gets that wrong, instead most will just waves around after seeing the runway and feeling waay too high (or just land at nearest patch of land).

Wonder, anyway, is the burn always done at the exact other end of the orbit ? I presume it's not ?

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1 hour ago, YNM said:

Didn't know that what they mean by s-turns are actually necessary for all descent. I think many of us gets that wrong, instead most will just waves around after seeing the runway and feeling waay too high (or just land at nearest patch of land).

Wonder, anyway, is the burn always done at the exact other end of the orbit ? I presume it's not ?

I'm not sure. It might help if you comment in the video, but I'm also not sure if Brett replies very often. In ksp, you might wanna try the trajectories mod. It gives you predictions. I'm sure NASA has other ways, but for KSP, that mod should help.

Edited by SpaceEnthusiast23
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2 hours ago, YNM said:

Didn't know that what they mean by s-turns are actually necessary for all descent. I think many of us gets that wrong, instead most will just waves around after seeing the runway and feeling waay too high (or just land at nearest patch of land).

Wonder, anyway, is the burn always done at the exact other end of the orbit ? I presume it's not ?

In order to perform well in the widely-varying aerodynamic situations of ascent, entry, approach, and landing (covering literally all possible velocity envelopes), the Shuttle had a very tricky re-entry profile. It had to keep its nose between 37 degrees and 43 degrees in order to maintain both adequate TPS coverage and adequate aerodynamic control; outside that narrow window, it would either have plasma impingement on unprotected areas (leading to burnup) or stall of its control surfaces.

But the Shuttle had to have a very good subsonic lift-to-drag ratio in order to make an unpowered glide-in landing. Even though its hypersonic lift-to-drag ratio was much lower, the lift at hypersonic entry was enough to reverse the descent completely while it was still bleeding off velocity. If you've ever flown a plane in KSP, you know that pitching your nose up to 40 degrees at speed will almost immediately result in a climb. Capsules don't have this problem, since they invariably have L/D ratios far lower than 1, but the Shuttle did.

And therein was the problem; the Shuttle couldn't afford to stall during entry or it would lose aerodynamic control authority. Control authority is a function of lift, and lift is inversely proportional to both airspeed and air density; if the orbiter started climbing while losing velocity, lift over its control surfaces would melt away and it would stall and tumble out of control.

Since banking points the lift vector away from the radial direction, controlled banking allowed the orbiter to maintain a steady descent angle (to avoid stalling) while still keeping the nose at 40 degrees. The rolling back-and-forth was used to maintain heading, though depending on initial orbital inclination it used longer curves in one direction or the other to produce changes in heading.

EDIT: All that to say, because the entry and glide angle windows were so narrow, the deorbit burn had to pretty much be in the exact same place every time (for a given inclination) in order to come down at KSC.

Edited by sevenperforce
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@sevenperforce Thank you for the re-clarification. I was referring to how most people would do it in KSP; S-turns and turning around are just a way to ensure the plane have enough glide, and usually KSP winged shuttles have much more lift. I was just saying that it turns out it isn't easy at all to fly the shuttle in RL conditions - the shuttle has to be guided down by a computer.

 

I... guess it's a justification to have MechJeb on in-game, it is indeed a hard job.

Edited by YNM
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1 hour ago, YNM said:

@sevenperforce Thank you for the re-clarification. I was referring to how most people would do it in KSP; S-turns and turning around are just a way to ensure the plane have enough glide, and usually KSP winged shuttles have much more lift.

IMHO, the critical difference is that the shuttle was dealing with a much more punishing re-entry and had localized TPS. Orbital velocity is much higher in KSP. Mk3 parts can handle re-entry from LKO at a wide range of attitudes and have pretty much equal thermal protection on all sides. If LKO was higher-velocity and Mk3 parts had TPS only on the underside, requiring a fixed high-AoA entry, then KSP spaceplanes would also have trouble with too much lift on entry. You'd have to use a ton of RCS or a bunch of reaction wheels to maintain attitude since you'd be losing speed much faster than you lost altitude. If you were flying in without reaction wheels or significant RCS authority, then you'd need to do something like the S-turns.

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