Suborbital hops.

[Frozen_Heart]

So I've designed an aircraft which can leave the atmosphere and go suborbital. So I'm wondering; what angle is it best to climb to get furthest for the least amount of fuel?

[Leszek]

Furthest High, or Furthest Horizontally?

Furthest high is easy. Just keep going straight up. I normally angle a bit to make sure I land in the water, if you don't angle be prepared to land in mountains. (Preservation of angular momentum will get you to land west of KSC.) There is no point in going vertical more then 270 kms or so. After 250 kms you are "high above" and can do more science. You will stay high above right to escape.

Farthest Horizontally is more difficult. I think just 45 will work best for shorter hops. (If your engine can just get suborbital.) For longer hops a more flatter approach works well. If you think about it, orbital is the whole planet and it is mostly a horizontal burn. In every case you want to keep vertical for a short while to get out of the lower atmosphere.

If you are using Deadly Reentry, flatter is essential. It reduces the impact of reentry greatly to come in shallower. Even suborbital will kill you if you come in too steep.

If you are using an aerodynamic mod like Near or Far, then 3600 DV is enough to get orbital. You should be able to reach anywhere on the world with that or less. With a light load, that is three of the longest 1.25 stock tanks and a lv-45 engine or LESS.

[Pecan]

So much depends on your TWR and speed/drag at any particular altitude, it isn't anything like as simple as 'angle'. The best you can do is experiment I'm afraid, although 45-degrees is always a good place to start.

[Jimbimbibble]

I would try to get your speed as high as possible on jets so you need to burn < 1 minute on rockets. I ascend steeply until 10km, then at around 10-15 degrees until 20km and keep it shallow after that to reach my max speed around 30km when the jets cut out for lack of air.

[tater]

I was sure this was going to be about ales in spacecraft.

[Progressm]

I was sure this was going to be about ales in spacecraft.

This makes me happy.

In fact, it reminds me to ask you guys about an idea I have about homebrewing a range of beers with an Apollo theme; IVB lager, Reentry Amber Ale etc. I better start a new thread for that, though.

[Claw]

This makes me happy.

In fact, it reminds me to ask you guys about an idea I have about homebrewing a range of beers with an Apollo theme; IVB lager, Reentry Amber Ale etc. I better start a new thread for that, though.

While it's a fine hobby, please no discussions of alcohol on the forums. And even if we could, it's a bit off topic for the thread (so you're right about starting a new one, but it'll be closed for alcohol content).

Thanks,

~Claw

[cheeseit]

You can get extremely close to orbit if you get going fast enough.

I had a U2 styled plane with one turbojet that could cruise at 30,000 fairly easily I was trying to see how fast I could get around the planet without going into orbit.

I can't remember exact numbers but my surface speed would be high above 2000 m/s and I would accidentally end up in orbit very easily. I tweaked it slightly so I can go up extremely close to orbit and drop off a small satellite at apoapsis and circularize with an ion engine and then take the SSTO home.

[Heagar]

Your approach for a paticular plane have to depend on:

• the TWR (Thrust to weight ratio)
  
• what kind of engine you are using
  
• it's behavior at flameouts if you use an jet engine
  

The higher the TWR, the shallower you can perform an suborbital trajectory, witch is limited of course by it's engines. A rocket engine will consume your fuel at an alarming rate, but you can archieve an very high AP (Apoapsis).

An jet on the other hand is saving fuel as long as you are in the atmosphere, But the AP will often not be that high, if you can establish one.

For that reason jet's are often used for spaceplanes, to witch you can alter your suborbital plane afterwards:

For the beginning you could e.g. build a very small plane with only one jet engine. Because flameouts doesn't matter with only one engine there should be no problems if they occur. Take two RAM air intakes for that engine, with should be enough.

Ascend:

After 20k altitude build up airspeed to 1400 m/s. At 26k altitude the jet engine will start to loose thrust. If a flameout occur, throttle down a bit to keep it working. Between 30-34k altitude you should reach an airspeed of 1870 m/s. Because the airintakes will work better the jets could be operated - depending on your plane - up to 45-54k altitude to keep an once archieved airspeed (with minimum thrust). If this airspeed is between 2300-2500 m/s you will have an AP at least out of the atmosphere up to 150k. And you will have an PE arround 30k at least - a suborbital hop nearly around the world.

[Frozen_Heart]

Thanks guys.

I'm finding ascending at just under 45 degrees seems to be working best. The aircraft has not many intakes and not much rocket fuel but a very high TWR. Max altitude it can fly is around 18k and 1000m/s before switching to rocket mode.