Skip-glide entry with capsule?

[Jestersage]

Is it actually possible to do a skip glide entry with a capsule in KSP -- and how can we tell it's such and not just "I have put the PE high, so it dipped briefly into atmosphere before coming in for a return"

From what i can tell, the heat shields have some amount of lift, and I assume the lift value is designed for such purpose.

[AHHans]

21 minutes ago, Jestersage said:

Skip glide: https://en.wikipedia.org/wiki/Boost-glide.

Well, I understand that article in the way that "boost-glide" means "extend range of suborbital flight by using aerodynamic lift". And, yes, you can do that in KSP: get a capsule onto a reentry trajectory and then either just point retrograde (with the bottom perpendicular to the direction it is flying), or angle the capsule a bit upward of retrograde. In the latter case you'll land a bit farther along your orbit.

As you mentioned this is not very useful with capsules in stock KSP. Not in the least because they don't have enough lift to really steer you to a certain landing spot. But when landing a spaceplane that's in my "toolbox" for getting the spaceplane back to the KSC. In particular when I do a reentry from the Mun (or Minmus) and need to aerobrake over multiple orbits (like I did in the trip that I did for the K-Prize).

 

[AHHans]

1 hour ago, Jestersage said:

Is it actually possible to do a skip glide entry with a capsule in KSP

Well, what do you actually mean with "skip glide entry"? And how do you define the difference from "normal" aerobraking? (And why would you want to do that?)

If you mean something like: "did an aerobraking pass and ended with a PE that was higher after the aerobraking than before"? Then I guess that's not possible with the capsules. But I haven't actually tried to do that. You can do that with a spaceplane.

1 hour ago, Jestersage said:

From what i can tell, the heat shields have some amount of lift, and I assume the lift value is designed for such purpose.

Well, the heat shields and the bottom surfaces of the capsules. But I don't think that will generate enough lift to raise your PE again.

[Jestersage]

10 hours ago, AHHans said:

Well, what do you actually mean with "skip glide entry"? And how do you define the difference from "normal" aerobraking? (And why would you want to do that?)

Skip glide: https://en.wikipedia.org/wiki/Boost-glide.

As stated in the article:

"The technique was used by the Soviet Zond series of circumlunar spacecraft, which used one skip before landing. In this case a true skip was required in order to allow the spacecraft to reach the higher-latitude landing areas. Zond 6, Zond 7 and Zond 8 made successful skip entries, although Zond 5 did not. The Chang'e 5-T1, which flew mission profiles similar to Zond, also used this technique.

The Apollo Command Module used a skip-like concept to lower the heating loads on the vehicle by extending the re-entry time, but the spacecraft did not leave the atmosphere again and there has been considerable debate whether this makes it a true skip profile. NASA referred to it simply as "lifting entry". A true multi-skip profile was considered as part of the Apollo Skip Guidance concept, but this was not used on any crewed flights. The concept continues to appear on more modern vehicles like the Orion spacecraft, using onboard computers."

TBH, it's useless in KSP pure vanilla play, since Kerbals are fine with 8g re-entry. However, if you want to re-enter a bit more precise, skip glide is one of the way to to land further down.

In real-life, skip glide is used for two things, aside from above

1. To avoid landing in place they have no business/ permission to.

2. Out of necessity, they want the re-entry to be more gentle, but retain the usage of capsule. This is used mainly either for delicate cargo return, or an astronaut who suffers physical issues, an re-entry from Moon or even Mars.
A test scenario developed during Constellation is the following: Suppose an astronaut is physically injured during moon landing. How to transport that person from moon to a medical facility, either using ISS or even a terrestrial facility?

10 hours ago, AHHans said:

If you mean something like: "did an aerobraking pass and ended with a PE that was higher after the aerobraking than before"? Then I guess that's not possible with the capsules. But I haven't actually tried to do that. You can do that with a spaceplane.

Well, the heat shields and the bottom surfaces of the capsules. But I don't think that will generate enough lift to raise your PE again.

Well, if that is the requirement to be consider "glide entry", I will try...

Edited February 10, 2020 by Jestersage

[Norcalplanner]

Using a lifting reentry as opposed to an actual skip glide is frequently done in RSS/RO. Many reentry capsules in RO have a descent mode which shifts the CoM slightly to make this kind of reentry easier to achieve.