Thrust limiter varying by pulse

[gilflo]

Hi

I was trying reentry on a spaceplane, trying several times several methods. So I made a quick save on orbitingat 100km, then try each time deorbiting via mechjeb then reentry.

After 3 or 4 times, nukes engines were working fine as well as RAPIER with mechjeb, manual control was also fine, then on the 5th times when I switch on manual, all my Thrust limiters  were pulsing from 0 to 100% very quickly. It was impossible to get a 100% steady thrust lim.

This happens on another plane this morning after few tries. I suspect Mechjeb to mess that, but jam not sure.

There is also a ton of large radiators everywhere (4 in the cockpit! ) and extendable radiators, but it looks like reentry is still impossible....whatever solution you try....

This passenger spacecraft was perfectly running on 1.0.4

 

Edited December 2, 2015 by gilflo

[worir4]

Are all your mods updated for 1.0.5? That may be the problem if not. Does the thrust limiter still change by it self if you turn of mechjeb?

 As for re-entry, I think those radiators will break of if you go lower down. Instead set your periapsis higher, maybe around 30km, You will bleed speed of more slowly but you won't burn up. 

Edited December 2, 2015 by worir4

[Engineer of Stuff]

Mechjeb can mess with you if you are controlling the object with it on. Make sure all functions are off. 

[Red Iron Crown]

1 hour ago, gilflo said:

There is also a ton of large radiators everywhere (4 in the cockpit! ) and extendable radiators, but it looks like reentry is still impossible....whatever solution you try....

Not sure what is going on with your thrust limiters (and I don't think it's MechJeb, it doesn't touch thrust limiters AFAIK), but I can help with this part.

You're having trouble because you're pointing near prograde, which presents the minimum drag aspect of your plane. When reentering, you want as much drag as possible to bleed off speed quickly before heat kills you. My technique for this it to point radial+, presenting the belly of the plane to the airstream and dramatically increasing drag and rate of deceleration, as well as spreading the heating over the entire craft instead of concentrating it in the nose. As the atmosphere thickens it will become tougher to stay pointed that way, but a high angle of attack will still be helpful. Sample reentry pic (this is a 1.0.4 plane but the idea still applies):

Don't bother with radiators, they're not overly helpful when screaming through the atmosphere.

[gilflo]

I tried the technic of high angle of attack on re entry, but under 45km it generally end with spin.

and i don't think that it would be the way to fly through overheat in the real life...

we need tiles or real shield to protect the skin as for space shuttle

[Red Iron Crown]

6 hours ago, gilflo said:

I tried the technic of high angle of attack on re entry, but under 45km it generally end with spin.

and i don't think that it would be the way to fly through overheat in the real life...

we need tiles or real shield to protect the skin as for space shuttle

High AoA is exactly how the Space Shuttle and X-37 reenter:

Spin is usually caused by changing mass distribution, if you have any fuel remaining transfer it to the tanks that are furthest forward. The tiles are already modeled in game, they are represented by the high heat tolerances of the spaceplane parts.

[gilflo]

Thank you Red Iron.

I just manage a succesfull reentry using high AOA with a lot of vernor engines to stabilize position.

But before that I burnt retrograde very steep from 75km to 52km so as to get a surface speed as low as possible.

At 52km I set SAS to Radial + and my SSTO turns to high AOA.

Question is: Is it better to enter at low angle with high speed, means longer time in upper atmo, then use the high AOA technique or high angle of reentry with slow speed by burning retrograde before turning prograde and use high AOA?

[Red Iron Crown]

There seems to be a sweet spot for reentry angle: Too shallow and the craft won't slow down quickly enough and just absorb too much heat up high; too steep and the craft will get to the thicker atmo before shedding enough speed. Unfortunately, there's not a straight "set periapsis to x" answer as it varies by craft and initial orbit, best to experiment a bit and develop a "feel" for it.