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[Graknorke]

Today I learned that there is someone who does humanised KSP fanart and has some sort of Toblerone fetish.
Some good learnings there.

[LoSboccacc]

you aren't taking advantage of their infinite TWR.

that makes me wonder, what would you obtain if the RCS tank would had a dry mass of 0 tons? infinite dv? finite dw until the last drop where twr becomes infinite? ah, maths and limits.

[TheDarkStar]

you aren't taking advantage of their infinite TWR.

that makes me wonder, what would you obtain if the RCS tank would had a dry mass of 0 tons? infinite dv? finite dw until the last drop where twr becomes infinite? ah, maths and limits.

dV goes to infinity as dry mass (including engines) goes to zero.

[Sean Mirrsen]

So, apparently I can make spaceplanes that reach orbit easily!
The problem is re-entry. No dangerous re-entry mods installed, only FAR.
See, in the upper atmosphere I find no way to grip enough air to slow my plane down. I rarely have a brief window of control (albeit very sluggish, difficult control) and slight monitored slowing down around 37.5-40k. Then, the ship looses control completely and starts spinning while face-slamming the thick atmosphere at 2+ km/s. Anyone know how to fix this?

Dumb FAR, allowing my spaceplanes to enter orbit easily and giving me hope about how I might've actually designed something that works, then tearing them up in re-entry.

*walks away, grumbling*

A simple and dumb way to address this is to shuttlecock. Give your plane a long, fancy tail, extending far behind the CoM. That way you might retain some form of aerodynamic direction, if not stability, when you reenter. Try not to have extra lifing surfaces up front, too. If you need them to take off, then move them to the tail instead - the extra leverage should make it possible to take off anyway.

[jocan2003]

So, apparently I can make spaceplanes that reach orbit easily!
The problem is re-entry. No dangerous re-entry mods installed, only FAR.
See, in the upper atmosphere I find no way to grip enough air to slow my plane down. I rarely have a brief window of control (albeit very sluggish, difficult control) and slight monitored slowing down around 37.5-40k. Then, the ship looses control completely and starts spinning while face-slamming the thick atmosphere at 2+ km/s. Anyone know how to fix this?

Dumb FAR, allowing my spaceplanes to enter orbit easily and giving me hope about how I might've actually designed something that works, then tearing them up in re-entry.

*walks away, grumbling*

Most likely your angle of attack was wacko during re-entry, a few degree off and you are spinning out of control. Also using RCS and strong enough reaction wheel force to keep you steady dring re-entry. I personally never go more than 6-7 degree and making sure my plane is fully aligned with the horinzon ( Using mechjeb to *lock* the plane) untill my speed is more manageable, re-entry can be quite long but its safe nonetheless

[sluissa]

Center of mass is also important. Remember it's likely much different from when you took off, and even significantly different from the last time you touched any notable amount of atmosphere. For the most stable flight charictaristics, on most planes (obviously depends on your design, but unless you've got something completely wacky it should work) you want most of your weight up front. Before reentry transfer any remaining fuel to your forward fuel tanks. Not applicable if you're gliding in on empty, but most people don't design their space planes to be THAT efficient.

Also, remember, shallow glide slope. A lot of things you could get away with in a capsule, you can't do with wings and FAR. Hit the upper atmosphere, stay there a while, you may not feel like you have a lot of control, but with patience you can use it to change your course and glide slope even at 40-50km, let it slow you down before you hit the thick soupy cement that is the lower atmosphere.

Also, I completely forget if it's modeled this way in KSP or FAR, but one thing surprised me at first when I used to play Orbiter and was trying to do reentries with winged craft. At high speeds and altitudes, you get the most lift with only a slight nose up attitude. Not more than 10-15 degrees nose up. Nose up more than about 35-45 degrees and you quickly begin losing lift and slowing down faster. I don't describe it well here, but it always felt a little counterintuitive while I was doing it. But it sort of makes sense if you think about it since you're basically forcing a stall and losing all the lift your wings generate. Might be something to think about if you're trying to do those 80-90 degree pancake reentries that science fiction keeps trying to tell us the space shuttle did.

[miauw62]

The monoprop engines aren't very efficient, and with only two you aren't taking advantage of their infinite TWR. If you replaced the RCS with the equivalent sized fuel tanks and used an LV-909 you could probably squeeze out almost twice the delta-v.

Replacing them with LV-909's actually reduces my delta-V to about 1150 m/s.

[miauw62]

The monoprop engines aren't very efficient, and with only two you aren't taking advantage of their infinite TWR. If you replaced the RCS with the equivalent sized fuel tanks and used an LV-909 you could probably squeeze out almost twice the delta-v.

Replacing them with LV-909's actually reduces my delta-V to about 1150 m/s.

Actually, I think there may be something wrong with kerbal engineer's fuel sim, since adding one 909 to the bottom gives me less dv than two 909's on the sides...

[Sheb]

Well, it make sense, doesn't it? You're adding extra weight to the craft after all. You'll have higher acceleration, sure, but less overall dV.

[McDonald]

No, no, the other way around: Less engines give him less delta-v.

[miauw62]

Two engines should have higher acceleration and twr but lower dv than one (since they, consume twice the fuel)
Turns out liquid fuel doesn't naturally flow up, while monoprop is magically present everywhere in the craft.

I fixed this and this is the current incarnation:

I use fuel lines to feed fuel to two girders that I have mounted two 48-7S engines on.
The picture lacks the goo capsules and the solar panels.

This setup breaks Kerbal Engineer though.

[Girlinhat]

Two engines should have higher acceleration and twr but lower dv than one (since they, consume twice the fuel)
Turns out liquid fuel doesn't naturally flow up, while monoprop is magically present everywhere in the craft.

Not quite.  They consume fuel twice as fast, but they produce twice the thrust and have the same fuel economy.  In effect, if you add multiple engines of the same type, then you get the same fuel efficiency, but higher acceleration.

IF they weigh nothing.  Going from one engine to two adds more weight, in the form of the engine, even if there's no other parts added, the engine does weigh something, and that does reduce Dv because it does add weight.  Depending on your design, it may not change much, and the extra speed may be worth it, but it IS a difference.

[miauw62]

I FUCKING DID IT
I LANDED ON THE MOON
AND NOT A "LANDING" THIS TIME, A PROPER LANDING WHERE THE SHIP DOESNT TOPPLE OVER
YESSSSS

Spoiler: big images (click to show/hide)

A precarious moment. It was balancing on those two landing legs and I was afraid to push any buttons to right itself.

BUT I FUCKING DID IT BALBJIAOBHABIOHSDIOBLHLBAHLIBDIOJAODGIZAOG

I DID IITTTTT YESSSSS

[BFEL]

I FUCKING DID IT
I LANDED ON THE MOON
AND NOT A "LANDING" THIS TIME, A PROPER LANDING WHERE THE SHIP DOESNT TOPPLE OVER
YESSSSS

Yeah, with all those craters and gravity that Mun is a BITCH to get right. I generally have to quicksave/load repeatedly to do so.
Seriously though, FUCK the Mun. Go to Minmus instead. Its nice there.

[miauw62]

I FUCKING DID IT
I LANDED ON THE MOON
AND NOT A "LANDING" THIS TIME, A PROPER LANDING WHERE THE SHIP DOESNT TOPPLE OVER
YESSSSS

Yeah, with all those craters and gravity that Mun is a BITCH to get right. I generally have to quicksave/load repeatedly to do so.
Seriously though, FUCK the Mun. Go to Minmus instead. Its nice there.

I did like 5 attempts, before determining that the place I wanted to land was too sloped and moving to another place like a kilometre above the surface, with the last fuel of my "transfer" stage (that really was only used to kill horizontal velocity and keep it dead).