Best way to launch a space plane?

[onlinegamesz]

I am trying to get my space plane into space, I looked at different options, option 1 is to fly the space plane directly into space but i figured out this is almost impossible to do because im running out of fuel. The 2nd option i tried is to launch the space plane with a bigger plane and on top of the atmosphere i decouple and my space plane continues, this didn't workout quite well too. Then as 3rd option I did the space shuttle style, the fuel wouldn't be a problem then, but I have a hard time stabilizing at launch, every time it does not go straight but it turns to one side and crashes, any tips on how to fix this? what is the best way to launch it? thanks

[AeroGav]

If you don't want to make an SSTO space plane the easiest option is probably to put jet engines on radial decouplers/structural pylons - arrange them symmetrically around the plane's centre of mass.   For example, if it's a large plane, putting four engines on, above and below each wing.    That way when you jettison them, they won't cause the plane to go out of control, though you might want separatrons or little winglets on the upper pods to stop them falling back onto the wing or colliding with the tail.

example - 

 

[Kryxal]

The real Space Shuttle's engines had a VERY large gimbal range for exactly that issue.  You might consider posting a picture of your craft so people can pick it apart and help improve it, we're a bit short on details here.  You may have seen that the usual ascent profile is getting somewhat high, then going very fast, then finishing the orbital insertion with rockets, but we don't know what you have.

[ILikeIke]

The best way to launch it probably depends on its design. If you're looking for a cargo hauler like the venerable STS a shuttle setup with strap-on boosters and a big fuel tank (possibly with engines of its own) is probably the way to go. When you build one of these, you may (I am not certain about the challenge rules) be eligible to participate in the Shuttle Challenge!

If you want to get a small crew transport to orbit, you may well be able to launch from a carrier aircraft, but keep in mind you're designing two separate aircraft in that instance.

If you want to demonstrate your aircraft design skills/really want a challenge, you should build an SSTO, which takes off and lands on a runway and goes directly to orbit (there's some general advice for how to do this in terms of how fast you should be going at what altitude elsewhere on the forum). When you build one of these things and fly it successfully, be sure to document your trip and give yourself the K Prize!

Good luck!

[AeroGav]

1 hour ago, ILikeIke said:

 

The best way to launch it probably depends on its design. If you're looking for a cargo hauler like the venerable STS a shuttle setup with strap-on boosters and a big fuel tank (possibly with engines of its own) is probably the way to go. When you build one of these, you may (I am not certain about the challenge rules) be eligible to participate in the Shuttle Challenge!

 

Space shuttles are probably the hardest to build because of off-axis thrust, asymmetric layout, and the cg shifting as your fuel burns off.

Try putting four boosters around the aircraft like this, that way everything is symmetrical, thrust , fuel etc.  so it should go straight and stay straight even towards the end of the burn.

Sounds like the airplane itself is flyable, and only narrowly falls short of getting to orbit on its own.   With assisted launches like like you can replace engines with good sea level isp for ones with a good vacuum rating on the orbiter itself - poodles, terriers, nervs, ions.  Just make sure whatever combo you choose has about the same weight as the old engines or the change may upset the handling. 

[Spricigo]

I'm a big fan of Dyna Soar alike and MAKS alike designs. Just keep in mind: heavy parts in front, drag parts in rear.

 

 

Spoiler

Spoiler

 

[Jarin]

6 hours ago, onlinegamesz said:

I am trying to get my space plane into space, I looked at different options, option 1 is to fly the space plane directly into space but i figured out this is almost impossible to do because im running out of fuel. The 2nd option i tried is to launch the space plane with a bigger plane and on top of the atmosphere i decouple and my space plane continues, this didn't workout quite well too. Then as 3rd option I did the space shuttle style, the fuel wouldn't be a problem then, but I have a hard time stabilizing at launch, every time it does not go straight but it turns to one side and crashes, any tips on how to fix this? what is the best way to launch it? thanks

I'm a huge fan of SSTO spaceplanes, especially after running a plane-only career in 1.2. With a bit of work, you can make SSTO planes do just about anything. There's a lot of trade-offs though, so it depends on what your goals are. If you just need a bit more dV to reach orbit (and since you're not opposed to staging), you could strap on some LF drop tanks to get you through the ascent phase, then mostly carry LFO on the plane itself for the last sprint to orbit after ditching the extra weight. 

[cantab]

If it's a spaceplane that takes off horizontally, then the simplest option is to add some drop tanks, or drop boosters if you also need extra thrust. Just take off normally and discard the tanks when empty

[onlinegamesz]

Thank you very much for the responses, on this feedback I decided to make a SSTO, but I don't have enough fuel even to dock with a space station, any improvements I could do? 

 

 

 

[Wanderfound]

 

1 hour ago, onlinegamesz said:

any improvements I could do? 

Declutter the design, use the bigger fuel-holding wing pieces. You don't need that much engine, and all of those intakes are making a lot of drag. One shock cone or intercooler can feed three RAPIERs.

Consider squeezing a nuke between the RAPIERs:

You also don't need anywhere near that much monoprop. A small tank in the cargo bay is more than enough.

Edited March 25, 2017 by Wanderfound

[AeroGav]

The mk3 engine mount has 3  mounting points for 1.25m engines, which you  are using .  However, it also has a 2.5m mount in the middle, which does not appear to have anything on it.    If you don't want to put an engine there, you should at least use a 2.5m rocket nose cone to cover this or you end up with monster drag.  The 2.5m node is treated by the game as a 2.5m stack ending abruptly in a flat plate.

Also,  for best drag you should attach 1.25m nose cones to the back of your rapiers, then offset them forwards inside the engine so they don't block thrust.   It's ridiculous but it's something you need to do given the simplistic way the game models drag.

Airframe - I suspect your CG is very close to the back of your ship.  You are controlling pitch with elevons and tailplanes that are also very close to the back.  Elevons and Tail planes raise the nose by pushing the tail down.    Because they are so close to CG, they will have to push down very hard to have any effect.    They must be producing nearly as much downforce as the wings are producing in lift - and creating drag to do so.   

You could address this by adding canards, but it's more important to do something about that rear CG.       All your fuel and cargo must be in front of CG.    When it's gone, your plane will surely be uncontrollable, and if it isn't, that means when laden, it is so nose heavy that it cannot be an efficient flier - the trim drag to keep the nose up must be enormous..

[ForScience6686]

You could do any of those options, just depends on what you want.  I have each example if you want to give it a shot:

Early Shuttle, controls are touchy on ascent, but understandably so with offset thrust.

https://kerbalx.com/ForScience6686/STS-3

Ride along, fun way to prove the concept

https://kerbalx.com/ForScience6686/Goose-x

Ssto space plane, with great fuel mileage

https://kerbalx.com/ForScience6686/SS-1

I don't think there is one best way, it depends on your goal, and what you enjoy.  

[onlinegamesz]

Thank you so much for the help! I followed everyones advice and I just went to my space station, docked and returned to kerbin runway again! (BTW my first ever space plane landing on the runway, I always failed and landed on grassland).

 

 

 

 

 

[AeroGav]

4 hours ago, onlinegamesz said:

 (BTW my first ever space plane landing on the runway, I always failed and landed on grassland).

 

 

 

 

 

Call the Ball !

 

[Coolwhip1280]

The best way to launch a space plane is by doing a shuttle style launch such as the one in my space plane and rover to Laythe video.