advice for a space plane to Duna

[Corax89]

Hi, I've recently designed my first suborbital plane and I want to put it on Duna by a horizontal takeoff. My main problem is the first stage that I use for the launch; I don't get to do something that puts the plane in orbit without using a fuel consuming monstrosity . My intention is to do it without modded parts so if you have any trick, advice or something I will be very grateful!! thanks 4 the help!

[RainDreamer]

Use turbojet to launch yourself out of atmosphere, then switch to nuclear and circularize. Get a lot of horizontal speed first with turbojet, flying for a little more inside atmosphere at the edge before pitch up and burn to space, since it has a lot of efficiency in atmosphere, so why not take advantage of that?

[capi3101]

Hmm...so you want to do a spaceplane to Duna, eh? I've seen a couple of thems just today.

The big trick with a plane to Duna is going to be designing it with sufficient delta-V to get there and back. By which I mean that once you shut off your jets, you've basically got a rocket with wings. It'll need 1090 to get to Duna and 1920 to get back, say 3000 m/s of delta-V plus a reserve in case of screw-up. That's assuming you want to try to do a round trip effort.

As far the Kerbin launch goes, you can handle it just like a regular spaceplane launch. Standard guidelines:

- 10 tonnes maximum takeoff mass per Basic Jet, 13 per RAPIER or 15 per Turbojet.

- No less than .03 intake area per engine

- A 1:1 total lift coefficient-to-take off mass ratio

- 40 units of liquid fuel and about 25 units of oxider per maximum take off mass (this assumes the use of RAPIERs, so take it with a grain of salt). This should be separate and distinct from the fuel you'll use to carry out the interplanetary portion of the mission.

I'll recommend nuclear engines as your spacefaring engines of choice for a Duna mission unless you can manage a really small design. Though they're heavy, their high Isp will let you get away with carrying less fuel than you'd otherwise need. I say that; others might give you different advice.

[Corax89]

Hey, thanks for the advice! I'll try it , but for the turbojet stage, do you recomend any specific configuration? I've tried before with RCS with a similar shape of that of Space plane from Virgin.

[Corax89]

Wow thanks capi3101, I will try to do it with that!

[Starman4308]

As far the Kerbin launch goes, you can handle it just like a regular spaceplane launch. Standard guidelines:

- 10 tonnes maximum takeoff mass per Basic Jet, 13 per RAPIER or 15 per Turbojet.

- No less than .03 intake area per engine

- A 1:1 total lift coefficient-to-take off mass ratio

- 40 units of liquid fuel and about 25 units of oxider per maximum take off mass (this assumes the use of RAPIERs, so take it with a grain of salt). This should be separate and distinct from the fuel you'll use to carry out the interplanetary portion of the mission.

Those are the standard guidelines for Kerbin ascents, correct?

He doesn't need something optimized for Kerbin ascent: he needs something optimized for a Duna round-trip, one which is capable of just barely waddling to orbit before tanking up on LF/O for the interplanetary portion. In that case, he'd probably want fewer turbojets, fewer intakes, more wings, and as much LF/O as he can possibly cram on there. It's probably possible to make something which can do both reasonably well, but I would still emphasize making a Duna spaceplane instead of an LKO spaceplane, and refueling from a separate SSTO in orbit.

Also, I'd advise against including Basic Jets at all: they're basically worthless for anything other than low-atmosphere, low-speed maneuvers.

[numerobis]

Don't diss the basic jet so hard; it can get you up all the way through the atmosphere on low technology tiers.

The turbojet is way better of course, but it's a higher tier.

Back to the OP: For lift, you'll need rather a lot more wings to land at Duna than necessary for liftoff at Kerbin (unlike the situation with Laythe). About 5x as many if my calculations are right.

Laythe is an easier target actually.

[Wanderfound]

For demonstration: http://forum.kerbalspaceprogram.com/threads/101944-Kerboduna-Part-1

That's with FAR, however. Stock soupmosphere would make it harder.

[kriseric]

Here's my approach to a Duna return space plane. KSC - Duna - Return without refuelling.

I went with parachutes instead of extra wings.

Javascript is disabled. View full album

[m4rt14n]

Thats a beauty

[panzer1b]

Duna is probably one of the 2 best SSTO destinations (after laythe), as its dV doesnt require 5 digit numbers, and it allows aerobraking to slow your orbit properly. its also not THAT difficult to return from provided you have a good plane with above average lift (most of my SSTOs do vertical landing on duna, since they are more or less a rocket with some wings strapped on or crammed internally).

A few tips i can say, nukes are the best engine (and dont suffer much dV penalty on duna), they have super good dV for all interplanetary burns, and the thrust is enough to lift a 20 ton craft with a single nuke (although it may be a little slow). As for doing orbit, you are most likely going to be best off with a jet powered rocket like design. Unless you are going to laythe, the jet engines are more or less dead weight that has no use whatsoever once you leave orbit, so use the bare minimum (or grab rapiers which can be used as good brakes provided you mnistime the brake burn on duna with a craft that needs to do this as it doesnt have the lift).

Edited December 14, 2014 by panzer1b