SSTO's in x6.4 Kerbin size

[Iguas]

Hey guys, today i need some help ! 

There's not a lot of people playing in x6.4 size, so getting help from existing post is pretty hard ! 

So basically i'm trying to make an SSTO capable of getting crew to a 200km space station, but it's not easy !

Even though i'm using SMURFF, the Delta V is VERY hard to get, so i went with a RAPIER + Wofhound design and i manage to get ALMOST enough Delta V, but i'd like some tips if you guys can do it easily !

My second issue come when i try to reenter, Deadly Reentry just slowly destroy my ship at about 80km even when i reenter at 40°, that's very frustrating, so what setting should i use for x6.4 size (5.5km/s orbital speed)

Thank you guys for helping me, and if you have other tips, i'll be happy to hear them ! 

Here's a little picture of da boy

Edited March 5, 2019 by Iguas

[bewing]

Exactly how many crew?

So what you need is an SSTO spaceplane with about 7000 m/s of deltaV? I think you're not going to have any choice other than going with a pure LF whiplash/NERV engine setup. It's going to be nearly impossible to do that with LFO -- unless you are willing to do some cheaty tricks such as engine clipping.

Spaceplanes are really tricky. You need to absolutely minimize drag and dry mass. Cut everything that you can. Ignore aesthetics. It won't be easy to fly.

So I think we're going to need a picture of what your current design looks like -- but once you've cut everything non-essential off, it may not look like that anymore.

As far as reentry goes -- 5.5km/s is horribly fast. You are going to need to get down to an orbit just above the atmosphere, then lower your Pe just inside. Then go to a 90 degree AoA, and hold it. Using SAS Radial Out in Surface mode is helpful. You need maximum drag, and you need to hold it as long as you can. If pumping some fuel around (to change your CoM) will keep the nose up for a few seconds longer, do it. If you have RCS fuel remaining, turn on RCS to hold your attitude. You have to get your speed down before you get to the death zone at 80km. Don't let it drop to a 40 degree AoA until you have no other choice!

Either that, or you are going to need to turn around and burn retrograde until you are at a survivable reentry speed.

 

 

[Iguas]

32 minutes ago, bewing said:

Exactly how many crew?

So what you need is an SSTO spaceplane with about 7000 m/s of deltaV? I think you're not going to have any choice other than going with a pure LF whiplash/NERV engine setup. It's going to be nearly impossible to do that with LFO -- unless you are willing to do some cheaty tricks such as engine clipping.

Spaceplanes are really tricky. You need to absolutely minimize drag and dry mass. Cut everything that you can. Ignore aesthetics. It won't be easy to fly.

So I think we're going to need a picture of what your current design looks like -- but once you've cut everything non-essential off, it may not look like that anymore.

As far as reentry goes -- 5.5km/s is horribly fast. You are going to need to get down to an orbit just above the atmosphere, then lower your Pe just inside. Then go to a 90 degree AoA, and hold it. Using SAS Radial Out in Surface mode is helpful. You need maximum drag, and you need to hold it as long as you can. If pumping some fuel around (to change your CoM) will keep the nose up for a few seconds longer, do it. If you have RCS fuel remaining, turn on RCS to hold your attitude. You have to get your speed down before you get to the death zone at 80km. Don't let it drop to a 40 degree AoA until you have no other choice!

Either that, or you are going to need to turn around and burn retrograde until you are at a survivable reentry speed.

 

 

Just posted a picture, 

I tried Nerva's/whiplash but their TWR is way too bad, and i can't manage to get out of atmosphere, but their ISP is way too good, so i'll try hard again to make it this way...

5.5 km/s is my orbital speed at 120 km, i CAN'T go under that ^^ (i'm in orbit with 200m/s DeltaV, so can't retroburn at all)

Here's a picture of the disaster 

Thank for your reply, i'll try Nerva's now

[Starman4308]

1 hour ago, bewing said:

So what you need is an SSTO spaceplane with about 7000 m/s of deltaV? I think you're not going to have any choice other than going with a pure LF whiplash/NERV engine setup. It's going to be nearly impossible to do that with LFO -- unless you are willing to do some cheaty tricks such as engine clipping.

He's running 6.4x scale with SMURFF, which explains the need for 7 km/sec of dV.

To Iguas: you are going to need to make a serious break from stock SSTO designs. These get the bulk of their delta-V from jet engines... whereas for you, you're probably looking at maybe 30% at most coming from jets.

I'm also unsure on how to solve your reentry heating problems, other than possibly writing an MM patch to increase the max temps of spaceplane parts.

If I may make a suggestion, though: a marginal SSTO makes the start of an excellent TSTO. If you're willing to install StageRecovery, you could potentially add a booster stage, separate that at roughly 1.5 km/sec, and finish the rest on a more vacuum-optimized design.

[Iguas]

21 minutes ago, Starman4308 said:

He's running 6.4x scale with SMURFF, which explains the need for 7 km/sec of dV.

To Iguas: you are going to need to make a serious break from stock SSTO designs. These get the bulk of their delta-V from jet engines... whereas for you, you're probably looking at maybe 30% at most coming from jets.

I'm also unsure on how to solve your reentry heating problems, other than possibly writing an MM patch to increase the max temps of spaceplane parts.

If I may make a suggestion, though: a marginal SSTO makes the start of an excellent TSTO. If you're willing to install StageRecovery, you could potentially add a booster stage, separate that at roughly 1.5 km/sec, and finish the rest on a more vacuum-optimized design.

Yup, i'm currently crying, i CAN'T DO IT xD It's very hard, That's sad, cause i liked the idea of space travel being like earth travel, with reusable and single stage plane, but i guess it's too difficult for me...

That's weird because some real life SSTO are almost working, and earth is x1.5 bigger than my kerbin ^^

Anyway, even a boosted shuttle couldn't fly because of reentry heating  i'm not sure if i want to edit my parts... seems cheaty  

[bewing]

Using MK3 parts is probably a mistake.

That's why I was asking you exactly what you want this spaceplane to do, once it gets to orbit. How many crew? Must you also carry some cargo?

The larger your spaceplane is, the harder it will be to make it reenter. And MK3 spaceplanes are very very large.

 

[Iguas]

4 minutes ago, bewing said:

Using MK3 parts is probably a mistake.

That's why I was asking you exactly what you want this spaceplane to do, once it gets to orbit. How many crew? Must you also carry some cargo?

The larger your spaceplane is, the harder it will be to make it reenter. And MK3 spaceplanes are very very large.

 

Crew is not the problem, but i want to make a cargo version later, maybe including KIS cargo in it, and MK2 size is too small, i can't reach orbit with Mk2 parts i think

[Aegolius13]

The compact Wolfhound counts as a 1.875 meter part, so I imagine it's generating a lot of necessary drag.  If you keep it, you could convert those side stacks to 1.875 as well, or maybe somehow put one on your center stack.  

It's been well said above at this point, but I'm skeptical that Rapier/Wolfhound is the ideal architecture for this job.  Might be worth trying Rapier/NERV, with just a little oxidizer to give your nukes a little extra time to work.  Yeah, the Rapier's ISP sucks, but the "free" thrust (from a mass and drag perspective) helps to make up for that.

You could save a little mass by using a lighter vertical stabilizer -- the Big S fin has way more yaw authority than needed.  If you could move your ailerons further back (or to the front), you might also be able to save a little mass with the same pitch authority.