Quick SSTO question....SO CLOSE!!

[Glaran K'erman]

Codenamed Flying Squirrel, I want this to work really really really bad. It's my first ever attempt at a SSTO and I wanted to do it without checking ANY advice, from the ground up I wanted to figure out for myself what made a SSTO work. But I have reached a point where I just need to ask a question. Basically, yes or no, can this work?!?!?!

Weight 15t

TWR 1.41/1.84

DV 8,476

And you can see I got my AP pretty high so I think the math might(?) work out that I can get it into orbit but I just don't know! So close!!!

Edited July 5, 2015 by Glaran K'erman

[Frank_G]

Hi Glaran. From your shown stats, the SSTO can make it. What i can tell from the picture is, you have too many intakes. 2 per engine is by far enough (i have a 12 engine SSTO that uses only 8 intakes). This will reduce weight and drag, giving you even more delta V and better acceleration.

What i can´t tell from the picture is, how the center of weight is in relation to the center of lift. If you switch on both markers, the center of lift should be inside the center of mass, just a little bit to the back and a bit more up for optimum stability. If you empty all your tanks, the center of lift MUST stay behind the center of mass, otherwise your SSTO will flip when it is almost dry. I hope this helps

[Glaran K'erman]

Yes! That just means I'm a terrible pilot and a not-so-terrible engineer! I can live with that. Here are the CoM screens by the way. Gonna keep it the vFranklin til I get it in orbit in honor for your help haha.

[Frank_G]

Here some piloting tips... get out of the denser atmosphere as fast as possible. At higher altitudes you will noticeably accelerate much faster. If you notice, reduce your ascent angle and get all the speed you can before nosing back up and switching to rocket power. Do not coast to apoapsis until you have reached space. Otherwise you will loose part of your precious speed to gravity and drag, so keep your engines running on low thrust until you leave atmosphere.

[mrclucks]

On topic: can't see your CoL and CoM pics but you appear to have active control surfaces in front and in the back( I assume the from are pitch control and the back are roll) but you don't have yaw control. It seems as though you have rapier engines and all rocket fuel parts. That leaves oxidizer left when you're out of liquid fuel. You'll have to show us the dv of your space plane when it is in closed cycle

Just from eyeballing it looks like your space plane will reach space at the very least, even with the unconventional wing design. If it'll actually reach space depends on the actual dv after flying in jet mode, your accent profile, as well as how much dv is there when you engage rocket/closed cycle mode.

On an kind of unrelated mode; what is the general accent profile for sstos?

[Glaran K'erman]

Update: I DID IT!!!!! Finally made an SSTO to orbit! Thank Frank again, for the piloting tip worked like a charm, noticed that acceleration bump but didn't realize I could take advantage of it for THAT long. Got it into a 239x131km orbit with 33Lf 44O left, just enough for re-entry!

Mrclucks, yea I constantly have issues with posting pictures but yea control surfaces are my next issue, behaves ok in dense atmo but as you move up it gets sluggish for sure, but now that I know how it's supposed to look when it goes well I realize it's not too bad for how few there are. Also learned I need a couple small linear RCS for space too...

[selfish_meme]

For Rapiers get fast low, at about 400m/s you will hit the power band of the Rapiers, from then on ascend as quickly as possible, above 10km push for 1300m/s by 12-15km, make sure you have an action group for your Rapiers they fade for a long time and you will lose speed, as soon as you stop accelerating switch mode and carefully pitch up to 20'. Then follow the top of the programs marker till your desired apoapsis.

[Glaran K'erman]

Everyone should learn how to build and fly an SSTO in this game, the experience teaches you so much. Like for instance selfish_meme I finally learned how to use action groups....don't look at me like that! But yea definietly learned not to let auto switch for you because it doesn't do it well enough.

[Dispatcher]

Good stuff, everyone! I've enjoyed the thread. The most difficult spaceplane I ever made in terms of getting to orbit (and back) was a rocket-only plane. This was several KSP versions ago and was before we got the Rapier. After much experimentation I ended up using IIRC 3 aerospikes. Obviously adding air breathers to a spaceplane makes it much easier to get into orbit. Version 1.0.4 ensures good results with the Rapier.

I comparison tested all engines and graphed the results (see sig line). However, these are vertically launched and not piloted in order to keep results more consistent. The Rapier Mix flight required that the mode change automatically. I'm sure that the already good altitude result would have been better by manual switching. I recall the ship flamed out and coasted several seconds before auto-switching to closed cycle, so manual switching is best, per earlier posts.

[Glaran K'erman]

Ahh long day felt better knowing I got that puppy into orbit earlier. Yea, knowing when to switch modes and doing it in a timely manner makes all the difference, you learn to appreciate every m/s.