Spaceplane re-entry in RSS/Realism Overhaul - Help Needed!!!

[hypervelocity]

Hi guys! hope everyone's doing great!

Let me cut right down to the chase and ask what's been puzzling me for the last few days.

I CAN'T get a single spaceplane to re-enter from LEO. I just CAN'T.

I am playing with RSS + RO + many realism mods in 1.0.4 - I have also tried in 1.0.5 and their corresponding mod versions to see if it was a bug or something, but I just cannot re-enter my spaceplanes.

Stability is not an issue, as the spaceplanes maintain attitude effortlessly until they explode. Almost always, the part that explodes first is the cockpit - I've used the mk1 cockpit, mk2, and custom ones - they all explode.

I have tried several designs, included wings on the bottom and starting right below the cockpit in order to provide some shielding - still doesn't work and the cockpit explodes at circa 80km (not even close to when things get interesting).

I have also tried many different angles of attack: I dived straight into my prograde vector, I tried keeping a 20° pitch, even 40°, but the cockpit always blows up in flames.

Please also note I'm doing it very gently, i.e. chipping my orbit down from 150x150km very slightly into the atmosphere.

I have tried light aircraft (3T), heavy aircraft (40T), and they all keep blowing up

I want my fancy MMH+NTO Luna Transfer Vehicle to be able to take my guys to the Moon and then return and land back like an airplane!  

If my above description sucks I can post images of the wretched spacecraft.

Many thanks in advance!!!! love you all!

PS: I'm THIS close to just sticking a big heatshield on the back of my plane and going butt-first (how am I going to turn around afterwards to land I just don't know...) please don't make me do this!!!!

Edited February 11, 2016 by hypervelocity

[MatterBeam]

RSS expects Realism Overhaul to increase the temperature limits of parts going through re-entry. They've been marginally successful with Heat Shields, but AFAIk, RO doesn't touch cockpits beyond increasing their size to improve their lift/drag ratio. As for airplane cockpits, I think they've actually got reduced temperature limits.

You have three options:

-Try and install radiator panels on your cockpit, and on parts adjacent to it. KSP radiators are astoundingly efficient at drawing heat away from parts.

-Use the inflatable heatshield mod (Chaka Monkey?) and use it as the nose of your plane.

-Go into the .cfg files dealing with cockpits and increase your temp limits.

[HebaruSan]

IRL, the shuttle orbiter did "S-turns" during re-entry. I tried to find the video where Scott Manley talked about this, but had to settle for this clip instead. Some people have disputed whether or not this was to "bleed off energy", but it might be worth trying anyway in a realism playthrough.

http://videos.howstuffworks.com/discovery/28986-coming-home-from-space-space-shuttles-s-turns-video.htm

[MatterBeam]

3 minutes ago, HebaruSan said:

IRL, the shuttle orbiter did "S-turns" during re-entry. I tried to find the video where Scott Manley talked about this, but had to settle for this clip instead. Some people have disputed whether or not this was to "bleed off energy", but it might be worth trying anyway in a realism playthrough.

http://videos.howstuffworks.com/discovery/28986-coming-home-from-space-space-shuttles-s-turns-video.htm

As far as I know, the S-turns were done well after the ultra- to hypersonic part of re-entry, mostly to bleed of speed before lining up for the final landing run.

The most important part of an RSS re-entry, in KSP at least, is to remove as much speed as possible in the upper atmosphere. I usually place a dozen air brakes and activate them at 100km altitude. This reduces the re-entry speed from about 9km/s to about 8km/s before I hit the stratosphere, which is critical for avoiding exploding parts.

Edited February 11, 2016 by MatterBeam

[NathanKell]

RO does indeed give spaceplane parts appropriate maxTemps. The 1.25m parts are modeled on X-15; the "Mk1" 2.1m parts are modeled on early spaceplanes (and don't have the tolerance of later parts), and the Mk2/Mk3 parts are STS-quality.

 

There are two routes to success here. Both rely on reradiating.

1. Shuttle approach. High ballistic coefficient (for a spaceplane), fairly low perigee.fairly high peak flux but low load.

2. Old-timey (50s) idea of the approach. Low BC, very low wing loading, very long time in the very high atmosphere (80+ km).

Using approach 2, I reentered with this:

Uh: I reentered that *dry* so like 14 tons. The stated mass is for ascent (it's the third stage).

Another note: don't have too high an AoA, you need to keep your perigee up.

[genericeventhandler]

Turning the plane in the upper atmosphere does nothing for drag,

Either: Enter from the minimum orbit you can maintain, turn retro grade and burn 100ms. Wait until the flames start and burn everything retrograde, then trun prograde and pitch up to 45 degrees. 

Or:

 if you have no fuel to burn retrograde pitch up to 75-85 degrees and present the bottom cross section to the atmosphere, causing the most drag. You need to get through the upper atmosphere as quick as possible in this instance and get down low where there is more drag to slow you down. Beware of detachable wings when using this approach.

GE

[hypervelocity]

thanks everyone, I will try all your suggestions today!

@NathanKell, many thanks for the specificity, I think your pointers will really get me there - just wanted to ask you, what does it mean in your first scenario "high peak flux but low load", and in the second, "very low wing loading"? (do you mean I should keep my wings empty of fuel?) - I am of course re-entering a dry aircraft as all the fuel was spent in previous transfers.

@MatterBeam thanks mate, I will definitely try those airbrakes at the upper atmosphere!!!

thanks guys, you are the best, very much appreciated!!!

Edited February 11, 2016 by hypervelocity

[NathanKell]

@hypervelocity you're most welcome!

During a reentry there's two things you need to worry about: heat load (Q) and peak heat flux (q"). The heat load is how much heat you take in; the peak heat flux is the highest flux you suffer at any instant. The heat load will be in joules, the peak flux in watts. You can watch your flux by turning on "Show thermal data" and right-clicking the leading part; convective flux will change over time, and the maximum it hits is q".

For a theoretical primer, see here.

By wing loading I mean craft mass divided by wing area.  The STS orbiter, for example, has a wing loading of ~580kg/m^2. That's at the high end for a spaceplane, though obviously lifting bodies would be even higher. When I talk about low wing loading, I mean something like 50-100kg/m^2.

[hypervelocity]

sorry for bumping this up again but I just cannot do it - I don't consider to be a quitter by I have seriously tried and still can't do it. I used to do it all the time in 0.90 but after 1.0.0 I just can't do it.

I have tried very very low BC & wing load, and the most time possible at upper atmosphere and still can't do it, even with the supposedly STS-class MK2 cockpits.

its always the cockpit that blows up

I know this is stupid but could someone share a craft file so I can try with your proven, certified creations?

Edited March 10, 2016 by hypervelocity

[Enceos]

@hypervelocity Have you tried the high BC reentry? Parts in KSP have two temperature maximums, one is internal temp the other is surface temp, if one of those reaches maximum then the part explodes. I suppose in RSS very low BC reentry takes too much time so the internal temp has enough time to reach its maximum. High BC reentry should give stress test to the surface temperature tolerance of the part and cut time for internal temperature build up. If high BC reentry makes your plane explode then you should go and edit your savegame persistent.sfs

Scroll a bit down to find this line

        DIFFICULTY
        {
            AutoHireCrews = False
            MissingCrewsRespawn = True
            BypassEntryPurchaseAfterResearch = True
            AllowStockVessels = False
            IndestructibleFacilities = False
            ResourceAbundance = 1
            ReentryHeatScale = 1  // play with this number to get the desired result (1 = 100% reentry heat, 0.8 = 80%)
        }

Edited March 10, 2016 by Enceos

[hypervelocity]

thanks for the prompt reply @Enceos !!!!

Before creating this thread my original approach was with high BC as I tried to design my spaceplanes as aerodynamic as I could, however couldn't re-enter them in 1.0.4 / 1.0.5

I knew there was the option to reduce the re-entry heat multiplier however I don't want to do that  I want to re-enter with the most real conditions as possible! :'( 

have a craft over there I could test? :$

Edited March 10, 2016 by hypervelocity

[Enceos]

@hypervelocity Do you use the RealHeat mod? In RSS reentry temps are a bit weird, this mod probably should fix that.

I don't play RSS so I don't have capable crafts to share, but I've been playing with temperatures for quite some time to get Inline Ballutes mod right, so I might know where to look.

[hypervelocity]

thanks!!! I did try and look it up in CKAN (tho not sure if was exactly this mod) and it showed as AD or deprecated, don't remember (yeah my memory's not that good anymore) - I will check once I get back home from work - hopefully this is the solution!

many thanks!!!!!!

[NathanKell]

Realism Overhaul requires it, so I would be shocked if you don't have it.

 

Can you take some screenshots during your low BC reentry?

[hypervelocity]

yup and I install everything via CKAN so I must have it.

I will set up some screenshots when I get back home from work

[Enceos]

On 10.03.2016 at 10:45 PM, hypervelocity said:

yup and I install everything via CKAN so I must have it.

I will set up some screenshots when I get back home from work

You work a lot  come back home already