Descend directly or in two fases (reentry)

[TheCardinal]

I'm wondering what the best method is to return an SSTO safely given an orbit of 350 KM. You can alter the periapsis of the SSTO to 45 KM at once from the 350 KM orbit or you could alter the orbit to 75 km and then alter the periapsis to 45 KM.

I have the impression that the second way is better. Is that nonsense or is that true? (If so, why?)

 

[Grumman]

When reentering Kerbin's atmosphere, you want to spend as much time as possible in the upper atmosphere. Too low, and you gain heat too fast and incinerate yourself, too high and you're not burning off orbital velocity for free. For that reason, I'd generally suggest entering an "orbit" of 55-60km and then pitching your nose up so that you're converting some of your lost velocity into lift and not just drag and thus can stay in that sweet spot for longer. On the other hand, doing it this way will make your eventual landing site less accurate.

Edited April 12, 2016 by Grumman

[KerikBalm]

the 2nd way takes more dV but will be a little better in terms of heating, as velocity at perapsis will be lower.

45km isn't very low... odds are from 350km, you'll go back into space again with a lower apoapsis, and basically accomplish the "75x45km option" using less dV (but making the timing of your landing more difficult).

I typically put my SSTO perapsis at about 30km, but that requires a relatively high AoA during reentry... and not using the mk1 spaceplane cockpit (the inline one is ok)

Edited April 12, 2016 by KerikBalm

[moogoob]

I re-enter my Nastybird shuttles with a 15km periapsis - works fine, IMO. See link in my sig if you want to see the type.size of craft. Haven't tried a more aggressive trajectory like mun return or anything though, but anywhere from an 80 to 360 km AP that works fine.  All I do is set the elevons to act as flaps to keep the nose up, then just use the atmo to slow down. I never even get heat readouts popping up if I do it correctly.

[Snark]

Moved to Gameplay Questions.