Landing an SSTO with Deadly Reentry & NEAR

[Broax]

Hi guys!

This is a sad question for me... So I'm trying to master a couple of before the next update(s) and one thing I'm trying to get used to is the aerodynamics of NEAR. I've been playing with Deadly reentry for a while and I don't have much problems with it when I'm using rockets and it's just a capsule on reentry.

But now I'm working on a SSTO design to manage crew transfers for a space-station. The station isn't built (like I said I'm practicing the concepts for a career game) but I was successful with making it to orbit with enough fuel left for landing.

The thing is I don't make it pass reentry... Stock aerodynamic parts don't (Wings, etc.) seem to have any heat-shielding built into them and my plane breaks apart upon reentry...

So can anyone share any tips on how to land an SSTO with Deadly Reentry and Near mods?

Here is the ship before launch:

And here's what happens upon reentry:

So... Can anyone help me please?

EDIT: I've got some extra info that might be useful... So when I hoover over the parts on the VAB it says they have ActiveHeatShield but when I hoover over the parts it says ActiveSheild=False... Maybe I installed DR incorrectly... :/

Edited November 3, 2014 by Broax

[Master Tao]

DRE adds reflective heat shields to all the new SP+ parts. The big piece is to use the improved aerodynamics in NEAR to slow down faster. Reenter at a very high angle of attack – 90 degrees when you hit the atmosphere, transitioning down to about 45 during maximum heating. You can also perform S-turns to bleed off velocity without covering much ground distance.

Of course, you'll have to design your spaceplane so that it can maintain high AoA during reentry.

[Broax]

DRE adds reflective heat shields to all the new SP+ parts. The big piece is to use the improved aerodynamics in NEAR to slow down faster. Reenter at a very high angle of attack – 90 degrees when you hit the atmosphere, transitioning down to about 45 during maximum heating. You can also perform S-turns to bleed off velocity without covering much ground distance.

Of course, you'll have to design your spaceplane so that it can maintain high AoA during reentry.

Thanks for the help... but wouldn't the isShielded:False on the wings imply I probably screwed the installation?

[Master Tao]

No, that's a FAR/NEAR message. It means you haven't put the wings inside a cargo bay or fairing. Probably a good thing.

[Broax]

Ooooh! Thanks a lot then!

I actually gave your tip a try and I actually made it pass reentry... Sadly the fuel I thought was more then enough wasn't but I managed to glide to the runway of KSC. But I came in too fast and the runway wasn't enough for me to stop... It was actually one of my first crashes in an airplane... Everyone died..

At least your tip proved useful to get passed the reentry heat and the other stuff is just things I can fix. What I now need help with is giving some extra stability to the craft in such a steep angle (90º) of reentry... I completely lost control of the craft and was almost by miracle that I managed to get it flying again...

Care to share some other tips on that?

[Hodo]

Part of the problem is you are going WAY to fast on re-entry. But on the good news is you figured that out. What I usually do with FAR+DRE is I have airbrakes on the craft to slow it down that I deploy from 40km down to 20km, to try and slow the craft down from over 2000m/s speed to less than 1400m/s. Once I am below mach 5, I can get it to slow down to subsonic by the time I am over the KSC.

I start my deorbit burn almost 180deg out from KSC. I set my PE for 2km above KSC. This is usually this perfect for most of my craft to come in and have to fire up their jet engines just as I hit the mountain range west of KSC.

[MarvinKitFox]

25500m, at speed of 2100m/s is simply too fast, too low for either DRE or FAR.

NEAR is more forgiving, but I think what is killing you there is thermal meltdown due to DRE.

Your re-entry needs to be at a much shallower angle, i'd say.

You might want to actually use a good chunk of pitch-up, and enough thrust to almost maintain level flight, when coming down.

[NathanKell]

On the contrary, NEAR is *less* forgiving. NEAR does not model mach effects, thus you have much, much less drag super/hypersonic, and thus reentries are much, much harder than they should be. Use FAR.

[Plusk]

This

25500m, at speed of 2100m/s is simply too fast, too low for either DRE or FAR.

and the best answer

Reenter at a very high angle of attack – 90 degrees when you hit the atmosphere, transitioning down to about 45 during maximum heating. You can also perform S-turns to bleed off velocity without covering much ground distance.

Of course, you'll have to design your spaceplane so that it can maintain high AoA during reentry.

Slow down and enjoy the view

[Empiro]

Come in at a shallower angle. I usually aim my PE at 28km. Pitch up and down to maintain a fairly constant temperature across your craft (I usually go for 900-1000 degrees).

If you have B9, air brakes are quite effective (maybe too effective), and can make descents much easier and faster.

[Broax]

Wow! Thanks for all the help!! :-) I'll try a shallower angle of decent then... And maybe give FAR a try.. But I have one last question befor I mark this as solved...

Some of you are suggesting entering with my nose pitching up at an 90° angle, the thing is mu ship becomes veeery unstable while doing that... Could you share some construction tips on how to keep my ship more stable under those conditions (shallow reentry with nose up at 90°)?

Thanks again everyone!! :-)

[Wanderfound]

As posted on the DRE thread:

1) Make your deorbit burn. If you're coming in fast, keep it shallow; if you've got enough DV to scrub most of your orbital speed in advance, you can get away with something steeper.

2) Your first job is to halt the initial drop. Forget about ditching speed or anything else, just pull the nose up so you can level out again. Pull up too hard and you'll flip out of control and/or break your wings, but too slow and you'll cook. I usually keep an AoA of 15° or so throughout the process, gradually pulling up as I go (actual recommended AoA varies based on aircraft, altitude and speed; you need to experiment for yourself). Aim to have it levelled out by 30,000m.

3) Now, watch the VSI and your temperature gauges (DaMichel's Kerbal Flight Data is very good for temperature monitoring). Gradually descend until the temperature is just shy of lethal (usually around 1,300°C on my planes), then hold that altitude until it cools. Once the temperature drops, drop with it. Stay alert and be ready to pull the nose up quickly if the temperature spikes; there's a fair lag between lifting the nose and stopping the heating, so if you leave it too late you're toast.

4) You'll probably find that you need to stay above 25,000m until you get down to Mach 5 or so. Decelerating above 25,000m is slow; decelerating below 25,000m is fast. As well as greater drag, the lower air provides enough grip to get some useful S-turns happening. If you can get your reentry speed below hypersonic and avoid the initial high-altitude cooling phase, reentry and landing is a much faster process.

[Broax]

I tried a reentry with a more shallow angle of reentry and I was able to make a successful reentry!! The only downside is that it took FOREVER!! I think I traveled over half-kerbin just to loose enough speed... But thanks for the help everyone!

As posted on the DRE thread:

2) Your first job is to halt the initial drop. Forget about ditching speed or anything else, just pull the nose up so you can level out again. Pull up too hard and you'll flip out of control and/or break your wings, but too slow and you'll cook. I usually keep an AoA of 15° or so throughout the process, gradually pulling up as I go (actual recommended AoA varies based on aircraft, altitude and speed; you need to experiment for yourself). Aim to have it levelled out by 30,000m.

3) Now, watch the VSI and your temperature gauges (DaMichel's Kerbal Flight Data is very good for temperature monitoring). Gradually descend until the temperature is just shy of lethal (usually around 1,300°C on my planes), then hold that altitude until it cools. Once the temperature drops, drop with it. Stay alert and be ready to pull the nose up quickly if the temperature spikes; there's a fair lag between lifting the nose and stopping the heating, so if you leave it too late you're toast.

Having an AoA of around 15º sure seems to help... And the Kerbal Flight Data is indeed very useful! Thanks for tips!

[Wanderfound]

Reentry can be done fast, but it's risky and takes some fuel. See http://forum.kerbalspaceprogram.com/threads/94343-Spaceplane-Speed-Challenge-IV-Up-and-Down for examples.

[Stratoroc]

After my first successful rentry using DRE and FAR here are some tips:

1) have a high PE. My deorbit PE was 35Km.

2) Airbrakes. I put 2 large airbrakes above and below the wing and the did pretty well while imposing very little torque.

3) maintain a constant-ish 5 degree nose climb. Since most of my designs are barely flyable with little fuel, and FAR means that any stall causes forces that rip planes apart, I try to refrain from aggressive maneuvers at hypersonic speeds.

Pitching up by 90 degrees is a great way to shave off speed up high, but that's only useful while SAS can overpower aero forces.

Reentry was a loong process this way, with a lot of gliding between 40Km and 26Km to drop speed down below 1.2 Km/s

[Broax]

There's a lot a people talking about airbreaks but I really have no ideas on how to make them... The only thing that occurs is using infernal robotics to get some movable joints in conjunction with some drag parts (like wings)... Am I too far off?

[Empiro]

The B9 pack has dedicated Air Brakes in the control section. I've definitely landed without them, but they make things much easier (almost to the point where it feels like its a bit cheating).

[Broax]

The B9 pack has dedicated Air Brakes in the control section. I've definitely landed without them, but they make things much easier (almost to the point where it feels like its a bit cheating).

You actually suggested that earlier but since you said it was too easy I thought I should try to manage without it... But I'll give it a go when I get home... :-)

Thanks for the tip! :-)

[Broax]

I hate to double post but I figure in this case it kinda makes sense...

Anyway, I would like to thank everybody for the great tips you've give me regarding reentry with NEAR and DR. I just made a couple of adjustments to my SSTO test ship and the whole crew (6 members) made it back in one piece! :-D

The air breaks of B9 really made the difference helping me slow down. I also added a couple of extra wings on a front to give a bit of control to the nose during ascent and descent (great idea) and remapped my action groups as they weren't correctly handling the engines and the air intakes. I also tried a shallower descent with a higher AoA on reentry.

All in all the ship handled great... There was a bit of overheat (1200º) at one point which kinda scared me but I managed to pull through and land on KSC. Although I wasn't able to do it on my first pass but nothing a go'ol U-turn can't handle! :-)

Very sadly though I did take a couple of screenshots with the whole crew celebrating on the runway but for some odd reason the screenies don't seem be saved... But either way it was night time so they weren't thaaat great... :-P

Once again thanks for all the help! Couldn't have made it without the community!

[Wanderfound]

How to do airbrakes without B9:

Set up pairs of overlapping control surfaces near the CoM. Use right-click tweakables to disable these surfaces in all axes. Set the upper one as a maxed-out spoiler, the lower one as a maxed-out flap. Use an action group to toggle them on and off.

[Hodo]

How to do airbrakes without B9:

Set up pairs of overlapping control surfaces near the CoM. Use right-click tweakables to disable these surfaces in all axes. Set the upper one as a maxed-out spoiler, the lower one as a maxed-out flap. Use an action group to toggle them on and off.

Or you could set the spoiler max deflection in the negative, and the other to max positive.

[Wanderfound]

Or you could set the spoiler max deflection in the negative, and the other to max positive.

Ooh, nice trick; hadn't thought of that. That'll save me a couple of action groups.

[Hodo]

Ooh, nice trick; hadn't thought of that. That'll save me a couple of action groups.

Glad I could help.