Tiny, easy-to-fly interplanetary spaceplane

[godefroi]

I've begun playing around with spaceplanes, and now, I'm able to successfully put them in orbit and return them (though the actual landing part still results in unplanned disassembly as often as not...). I'm interested, however, to know just how small they can be made, and still be capable of big things.

I've put together an 8t plane, and I can orbit and return it, but it's got very little dV once it makes orbit. I've built a 10t plane that has ~1km/s dV in low orbit, and somewhere along the line I put one together that was between 15t and 20t that had ~1.5km/s dV in LKO.

My question is, is there an easy way to put one together (with stock parts) that had, say, enough to make Duna orbit and return without refueling? How about making Laythe orbit? Can it be done in less than, say, 25 tons?

I assume this is going to involve an LV-N for the extraatmospheric flight?

[Anton P. Nym]

My question is, is there an easy way to put one together (with stock parts) that had, say, enough to make Duna orbit and return without refueling?

It's actually tough to do; right now the best I can manage is single stage to Munar orbit and back for crewed craft, or Munar landing and back for a lighter probe. That's without the heavy LV-N, using the LV-909 for its lower dry mass.

It can be done, I've seen videos of people doing it, but it's not easy.

-- Steve

[cerberusti]

This SSTO spaceplane gets 4 kerbals and a full set of science gear to a laythe landing and back without refueling at 60 tons launch weight (one sits in a chair on the front landing gear for easy samples.)

http://steamcommunity.com/sharedfiles/filedetails/?id=239385512

Without the science gear it should be substantially less mass to do this, even more so if you use a probe core or a chair.

Edit:

It does use an LV-N, and includes a lab in the science gear.

It is somewhat close on DV (although I did not wait for a transfer window.) I hit laythe directly on entry into the system (with an over 70G aerobrake) and used a gravity assist from Tylo to return (which took a few quickloads until I had a course I liked and enough DV that I thought I could return.)

Edited March 30, 2014 by cerberusti

[KerikBalm]

Its too hard and inefficient for me...

I just build SSTO lifters.

Its easy enough to build a SSTO spaceplane that can lift large payloads (my most recent was 83 tons)

My "fully reusable Zero Debris" to duna missions involve:

* Large spaceplane lifts an LV-N powered interplanetary transfer stage and a SSTO Duna lander.

* Large spaceplane lands, Interplanetary stage goes to Duna

* Lander + IP stage begins aerobraking as one unit

* Lander separates and lands while, Interplanetary craft circularizes into low Duna orbit.

* Lander launches, docks with IP stage, and refuels

* Lander remains in orbit for future use, IP stage returns to kerbin

* IP stage aerobrakes and circularizes.

* Large Spaceplane refuels the interplanetary stage

Everything is reusable, but trying to move them all together as one craft is... IMO wasteful and inefficient

I could bring the Duna lander back with the IP stage.. but what is the point? Much more elegant IMO, to leave a fully fueled lander ready for use by the next mission (so the next mission can simply bring a fuel tank to set up a fuel depot, rather than another lander)

For sure, I can get my spaceplanes to the mun, or to Duna... getting them back is another story...

No spaceplane I send to laythe returns. Every SSTO lander I make, I leave in orbit (preferably fully fueled, or at least fuelled enough to de orbit and then get back to orbit) rather than carying it back (I'm assuming spaceplanes are the most mass efficient SSTOs for use on Laythe, I also like that they launch themselves, and I only need to launch additional fuel for them/something to push them to laythe [some have enough fuel left over to reach orbit from laythe's surface, and thus for a single mission just need a boost, not a refuel])

[SSSPutnik]

http://forum.kerbalspaceprogram.com/threads/57197-The-ultimate-Jool-5-challenge-land-Kerbals-on-all-moons-and-return-in-one-big-misson?p=1021230&viewfull=1#post1021230

31t to all Jool moons and back. Might give you some ideas.

[Kasuha]

This spaceplane may be ugly but it has 13 t and it can go to (and return from) Minmus, Mun, Gilly, Ike, Duna, and Laythe. Some of these are very tight on its ~3000 m/s of space dv. It can land (with no return) on some other bodies such as Eve.

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In general, for a spaceplane to have big range, you need to use LV-N. And since it's big and heavy, you need a lot of fuel, making the plane even bigger and heavier.

[John Crichton]

Difficult to build a small SSTO using only stock...but if mods are allowed, here's an antimatter Alcubierre drive thermal turbojet SSTO that can get anywhere in the system and back again. Can land pretty much anywhere but Jool too.

Check out the K Prize thread for inspiration: LINK

[Joonatan1998]

In 0.23.5 you may be able to use the ion engine for light interplanetary planes.

(Actually you already could, it just takes too much time for most players)

[capi3101]

Key thing about spaceplanes is that once they're in space, they're a rocket. They fly just like any other rocket, too...it's just the launch and landing mechanisms that are different. So a flight to Duna is going to be about the same as it would be for a rocket; it'll need about 2,140 m/s of delta-V to it to make a round trip between Kerbin and Duna. You will need some additional fuel to finish out the ascent on Kerbin, of course...say around 200-250 m/s of delta-V if you handle the ascent correctly. Make it an even 2,400 m/s and you should be golden.

So building one...general guidelines:

One Turbojet engine per 9-12 tonnes of payload. The more intakes you add, the more payload you can get per tonne of craft.

200-250 units of liquid fuel per Turbojet. That'll either give you enough to do some flying around for a landing zone when you get back to Kerbin or give you enough to still make orbit in the event of a bad ascent.

One pair of swept wings or delta wings per six tonnes of craft.

No fewer than three Ram intakes per Turbojet. A 3:1 ratio will give you the 9 tonne per engine payload capacity; each full number increase in the ratio gives you an extra half-tonne of capacity to the maximum of 12 tonnes per engine at a 9:1 ratio.

Assume a pair of nuclear engines for the transfer. A no frills spaceplane will have a Mk-1 cockpit, maybe a Reaction Wheel, a Z-1k battery and a pair of unshielded solar panels, its flight equipment and let's say....a pair of AV-R8 winglets for vertical stabilizers. Landing gear is mass-free, so we won't worry about it. You're looking at 6.175 tonnes plus the mass of the flight equipment as your payload mass in space. With a set of flight of equipment added for a light plane - one turbojet, two Mk-1 fuselages, three pairs of swept wings, four small control surfaces, and nine Ram Intakes - adds 3.83 tonnes to that mix. 8 FL-T100 tanks - or a pair of FL-T400s -would give you 2,552.867 m/s of delta-V (2,884.563 actually, since that mass assumes the Mk-1 Fuselages are full and they most certainly will not be once you've reached space), and your total craft mass would be just over fourteen tonnes.

Laythe is going to be trickier, on account of the higher delta-V requirement - you're going to want a craft with at least 6,000 m/s of delta-V to it. 6.175 tonnes plus flight equipment...you'll need three sets of flight equipment (one engine, 2 Mk1 Fuselages, three pairs of swept wings, nine intakes) at 3.73 tonnes each, adding 6.69 tonnes...48 FL-T100s equivalent will get you the fuel you need to get there (6,048.8 m/s of delta-V assuming full tanks) and the craft will have a mass of 44 tonnes. You might be able to land that craft on Laythe and get it back again but your fuel is going to be tight.

Anyway, those are general suggestions; do with them as you will.

[cerberusti]

The ratios capi gives are pretty much what you need, but there is one major point he left out:

Reduce drag everywhere you possibly can.

Use MK2s, one nuke engine (you can do two if there is no real payload... or you could nearly halve the size of the plane), and as little rocket fuel as you can. The biggest drain by far on a spaceplane is drag.

Laythe is very easy to take off from. Your ap should be very high when you exit the atmosphere, and you may even be able to escape it on nothing but jet engines.

[carazvan]

You definitely want to look at the SSTO challenge thread as you have many options there and ideas on how to build your own eventually:

http://forum.kerbalspaceprogram.com/threads/11214-The-K-Prize-100-reusable-spaceplane-to-orbit-and-back

[O-Doc]

I'm a big fan of using drop tanks on space planes. Mostly because I can configure the payload for the mission requirements but also, I can shed excess weight as I use up fuel. Thus, increasing my dV along the way. If you want something basic then have a play around with the upgraded MKII version of my BSC entry. You will get around 5k dV@LKO with that setup.

The only other small(ish) space plane I've posted on this forums is the Spectre which gets over 6k dV@LKO. Highly recommended for cruising around the Kerbol system, or the KSC.

This is a pretty good setup. If you want more range in this weight category then, I recommend you go for the two turbos and a nuke setup. That's my best long range SSTO for under 30T, I'm getting over 7.3Km/s dV@LKO on it. I haven't share that file...yet.