Stupid jet plane tricks

[numerobis]

Some people get suspicious that jets can go suborbital, so I decided to take the next step: orbit. I achieved a 100km x 270km orbit, and then I closed KSP without taking a screenie. Oops. But you can do the math to check:

1. a turbojet

2. a Mk1/Mk2 adapter

3. lightest pod, and the small battery

4. cube struts so we can mount the intakes behind the engine

5. 48 ram intakes clipped together

6. Control surfaces, for control (not infiniglide spamming).

Total mass on launch: a bit over 2 tonnes.

For sanity, I modded an intake that has 12x the mass, area, and resource space, so I didn't need to have quite so many parts.

Before launch, click on 24 of the intakes (or two of my modded intakes), close them, and disable fuel flow (when you right-click on the intake, click on the little green arrow and turn it into a little red circle). Now you have 2.4 units of air.

Fly a nice shallow path; I used a mechjeb 25% climb slope starting at 2km and ending at 30km, preventing jet flameouts, but not following terminal velocity. This uses up as much fuel as possible (reducing your mass at circularization time), raises the periapsis nicely (about 40km for me), and doesn't take too long since you're going more than twice terminal velocity. I canceled the ascent as soon as I got out of the atmosphere.

At apoapsis, click on that red circle in the intakes again -- but DON'T open the intakes. Your surface speed is around 1600-1700 m/s so you get more than half thrust, Isp is 1200s, and your mass is just shy of 2 tonnes. 2.4 units of IntakeAir is just enough to pull periapsis up.

This isn't exactly practical, but it is a fun perversion of the system.

[HoY]

The firespitter pack has a part that stores 100 units of intake air, to save you the hassle of modding the intakes or spamming them to that extent just for the extra storage

[Pixel of Life]

The firespitter pack has a part that stores 100 units of intake air, to save you the hassle of modding the intakes or spamming them to that extent just for the extra storage

Oh yes, the air tank! Love it, I use it on my spaceplanes all the time Although you do need TAC Fuel Balancer to set the intakes to "Out" mode and the tanks to "In" mode so that the air in the tanks will only be used when the intakes can't supply enough to keep the engines at max power.

[Pds314]

Wait, so it is actually using stored air for this?

That is an interesting way of getting into orbit.

I have definitely got regular hypersonic planes without cheaty numbers of air intakes (only 1-2 per trubojet engine) to suborbital flight, it isn't that hard, just hover at 15-20 km until the thing is moving mach 1600 m/s, shoot up using your wings, and there you go, you are now suborbital as you had enough speed to fly straight up for 160 seconds, averaging 800 m/s, ignoring air friction, that should get to around 148 km high. If need be, you can lower engine power and do the same at higher altitude and speed to avoid air friction and get a boost.

[numerobis]

At 1600 m/s you are quite far short and will need to carry rather a lot of air.

The concept of bringing oxidizer to use your jet beyond atmospheric flight makes some sense (it's what the Sabre people are proposing). You wouldn't bring air though, since it's mostly inert; and you wouldn't be getting better efficiency than a nuke.