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Ar-cen-ciel

SSTO Reentry at 7km/s in Real-Scale Earth?

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I've been trying to fly the GN Drive powered (vertical) spaceplane over the Earth in Real Solar System for quite some time now.

The problem, though, is that I never managed to really shed off the orbital speed during the atmospheric entry, and attempting to land the SSTO at that speed resulted in the ship itself blown up like fireworks. The only way I could find so far is perform a reverse-thrust with the GN engine in docking mode, but I'd like to find another way if possible.

I'm using the stock parts for now, though I would like to have this problem solved before I install more advanced mods like FAR.

Edited by Ar-cen-ciel

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The main issue here is that KSP fudges atmospheric heating physics upwards, due to its reduced scale. If it were realistically simulated, then reentering at 2 km/s on stock Kerbin probably wouldn't even give you a visible plasma trail, nor any danger of overheating. When you now scale Kerbin up to 11x size using RSS, you have a problem: you're trying to do reentry at fully realistic orbital speeds, using physics settings that are designed to make it harder and hotter than normal. This obviously doesn't work out all that well for most that try it.

Generally, you would install RSS together with Realism Overhaul, which ships a proper set of physics constants for real scale atmospheric heating, among other things. The more realistic aerodynamics simulation of FAR helps as well - planting a large surface, such as the belly of a spaceplane, squarely into a hypersonic airstream slows you down better in FAR than in stock. But if you don't want to go that far just yet (</rimshot>), then turning down the reentry heating slider in the difficulty options is a good start. I don't know what you have to set it to in order to get a stockalike experience, you'll have to experiment until it feels right.

Edited by Streetwind

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Well, the fact that you are using a mod that changes the scale of everything makes advice a little more complicated. However, there have been many many threads on these forums giving generic about getting spaceplanes to reenter successfully. So searching for "spaceplane reentry" may get you information overload ... um, I mean, exactly the advice that you need.

In general, though -- to get a spaceplane to the ground requires a "correct" reentry flight profile (and sometimes a retroburn is the only way to get it down in one piece). Which flight profile is the correct one depends tremendously on what parts your spaceplane is built from, especially their heat resistance, aerodynamic lift, and drag properties. The flight profile includes: what do you set the Pe to before reentry, and what AoA do you maintain through the extreme upper atmosphere, the middle atmosphere, and the point of greatest heating.

So, your original post gives the impression that you've tried every possible combination. Which means there's nothing left for us to tell you. :wink:

But if you haven't tried all possible combinations yet, then we need to know what you've tried. Have you tried putting your Pe just a few Kms into the very top of the atmosphere, setting your AoA to 90 degrees, and just riding it down that way to see how far you get?

 

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I'm trying to land this spaceplane back to Earth. All attempts to landing it apart from slowing it down with reverse thrust to less than 5km/h, ended in failure. Tried setting the periapsis to 60km or so, the plane blows up at 0-90 degree of AOA. The point of greatest heating is at the cockpit at the front of the fuselage, since it was pointed head-on in all my reentry attempts.

I've set the atmospheric burn to 0%, but the reentry heat is still there. Another noteworthy mod that might concern the problem is RealHeat, though I'm not entirely sure whether it is the culprit, especially since I didn't have FAR installed yet.

Edited by Ar-cen-ciel

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If that thing really does have infinite deltaV, then you might as well retroburn. :D 

After it blows the hell up, you should get a mission report screen that tells you which part blew up first. That info might be useful.

You might also want to scale down your retroburns, to find out the minimum amount of retro that it takes to make things work.

Do you have all your temperature gauges and thermal overlays turned on, so that you can Esc and pause and give it all a good looking over, every few seconds?

How long after reentry into the upper atomosphere does it blow? How many Kms do you descend?

 

 

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I didn't quite record it but I think the spaceplane would start heating up from 70km or so, and blow up at the altitude of around 65-55km.

Decided to remove RealHeat mod and voila, no more overheating at reentry anymore. Not sure how the spaceplane itself would've fared at 100% atmospheric heating in default setting, but at least the plane doesn't overheat into meteors anymore.

Edited by Ar-cen-ciel

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