SF-1D Condor

[Comrade Jenkens]

I found the Condor's design lurking in some of my old files back from 0.20 and decided to update and improve what is pretty much my only functioning SSTO ever. I stripped out the old turbojets and aerospikes and installed 6 Rapier engines which have given it a much better TWR throughout the entire climb. I've also had to wire in batteries, reaction wheels and an RTG due to the fact that electricity wasn't required back then! I also decided I wasn't at all happy with the cockpit and so ripped off the front of a Bat'leth Shuttlecraft I nicked from Rune which IMO has provided a much more consistent look considering its size. Though its quite short ranged the Condor can take 3 kerbals up to a 400km orbit to dock with a station and then return them back to the KSC with a bit of liquid fuel left for the final approach.

If you fancy you can drain the oxidiser and end up with a fast and high altitude aircraft capable of a full circumnavigation round Kerbin or Laythe which is surprisingly manoeuvrable considering its sheer size.

I've made a few changes and updated the craft file. The main difference is that I've changed the angle of the intakes to match the wing profile which looks a lot better. (screenshots are still older version). I've also slightly shaved the weight and also added an extra intake per engine. I've tested the Condor up to a 600km circular orbit and return and I reckon I can push it to 700 now.

Most recent changes are a pair of jr. docking ports to allow the Condor to carry 2 small satellites to orbit inside the wings.

Craft File: SF-1D Condor

Burn to orbit.

Above view shows the cleaned up intake profile.

A kethane and a science satellite delivered to a 250km polar orbit.

Landed back at KSC.

Edited February 12, 2014 by Comrade Jenkens

[Comrade Jenkens]

Ok I've heavily changed the cockpit area so it should look a bit nicer now.

[Rune]

It looks cool, but I'm wondering if your range/payload issues are not a direct consequence of your high T/W. Engines are heavy, after all, and RAPIERS especially so. Have you tried with just four? You seem to have enough wing to fly, and keeping the fuel and intakes while taking out engines will allow you to fly higher, so you might even end up transitioning to rocket power going faster. And it guarantees more delta-v or payload, increasing the mass ratio.

Or even better (though it won't work with that tail): five engines. Then you can forget about flameouts, since the last engine you place on the SPH is the first one to flame out: put one on the center last, and you get no thrust asymmetry during the flight. This is my current crew SSTO, flies like a charm on three engines (I had almost forgotten about it, I should release it!):

Rune. For SSTO's, the less T/W they can fly with, the more performance.

Edited February 11, 2014 by Rune

[Comrade Jenkens]

It can get into space with just 4 engines but its painfully slow. I did place the engines so the closest to the centre of mass flames out first so it gives you time to switch to rockets. Also I may add another intake per engine as it only has 3 per engine atm.

As I initially designed it as a fighter there is not really any place to put a useful payload on it (except maybe some small satellites between the wings.) Also due to an aesthetic choice the very rear part of the wing creates more drag than necessary.

I'd like to get better at SSTOs but they are so much more difficult than rockets.

Edit: Wait last engine you place not the first! I'll correct that straight away as that means this thing is a flying death-trap!

Edited February 11, 2014 by Comrade Jenkens

[Spartwo]

I'd like to get better at SSTOs but they are so much more difficult than rockets.

This might be your problem,think of it as a rocket.Give yourself ~2km/s and try to get that as high into the atmosphere as possible.

@Rune.I can barely stay airborne with four engines.

EDIT:as a proof of concept.

24 tons.Ballistic trajectory.2074m/s rocket d/v.A metric f*****n of liquid fuel (540)

Edited February 11, 2014 by Spartwo

[Rune]

This might be your problem,think of it as a rocket.Give yourself ~2km/s and try to get that as high into the atmosphere as possible.

@Rune.I can barely stay airborne with four engines.

EDIT:as a proof of concept.

http://i.imgur.com/KCDG32o.png

Hahaha. That's because you are looking at it from a completely different perspective! You are basically saying to treat SSTO's like rockets, not planes. And I'm more of the idea that planes are planes, and rockets are rockets, and you can SSTO both of them.

Let me explain further: you can't fly on four engines (or however many), because you don't have enough wing. But you could always fly on thrust, of course, if you add more engines. That is perfectly valid, and the logical extreme is forgetting about the SPH and moving your SSTO business to the VAB. Perfectly doable, and very easy as you say, just make it get off the pad with enough rocket delta-v. But that way you are building rockets, not planes. And there's also the fact that engines have considerable weight, especially airbreathers, and wings you could consider free, mass-wise.

So what happens if you build a proper plane, with T/W considerably lower than 1? You need lots of wings. That makes it big. But it has much less engines than a T/W>1... which makes it lighter! Much, much lighter. Basically what that means is that you will always get a bigger mass fraction in a SSTO if you spam wings, not engines. Now that extra payload to space could be extra fuel (so, more range), or plain payload (so a smaller SSTO for the same job). Always consider that while the climb might be long, the extra aviation fuel you consume is probably peanuts compared to the total mass of the SSTO. And even my slowest ascents never take more than 15minutes, 10 of which I spend websurfing while I climb over 10,000,.

Now the other thing is rocket takeover speed. But I won't get more into that, because basically it is a function of intakes, the more you have, the faster you go, and the less rocket delta-v you need. As simple as that. So considering these points, my requirements for a winged SSTO that aspires to do more than a VTOL SSTO ever could (be it range or payload) would be about balancing these two factors: as little engines and as much wing as I can, while still being able to climb at 10,000m, and on the other hand, as many intakes as I need to get fast enough for my rocket delta-v to get me to orbit. As you can see, the less engines you take because you can use wings, and the less rocket fuel you use because of intakes, the lighter you vehicle becomes. And that means payload fraction to orbit, ultimately.

Of course, that also means that by the time you get to orbit, if you can refuel, all that airbreathing equipment becomes useless and a dead weight. But a smaller dead weight that if it was composed of engines!

I should also mention how the faster you transition to rocket power the less rocket T/W you need, that is another weight saving, but it is a little besides this particular point, and I've said it enough times. Bottom line: fast climbs to orbit come at a price, and a heavy one.

Rune. In engineering, everything is a trade.

[Mesklin]

I agreed with every words Rune about winged and unwindeg SSTO, see another one proof of it:

6 kerbals on board, 25-30 minutes to LKO (but this bird stable enough for fly almost all time with 2x-3x physical warp), ~600 m/s dV on orbit and only 1 turbojets

[Spartwo]

Don't forget 8 tons lighter.What would be the weapon outfit?

[Comrade Jenkens]

I've managed 600km circular orbit and return now. Still using 6 Rapiers.

Next change will be adding 4 jr. docking ports so it can deliver a cluster of small satellites to orbit. I'm not going to bother adding weaponry as people seem to have lost interest in the military stuff.

[Rune]

I've managed 600km circular orbit and return now. Still using 6 Rapiers.

Next change will be adding 4 jr. docking ports so it can deliver a cluster of small satellites to orbit. I'm not going to bother adding weaponry as people seem to have lost interest in the military stuff.

Hey, perfectly valid to brute-force your way through the atmosphere in an almost vertical climb. Makes for fast rendezvouses, from the players perspective (what we call "long climbs" are actually more similar to standard rocket climbs than many think, the main difference is you can only timewarp for a far smaller fraction of the suborbital arc).

But perhaps a last suggestion to milk a bit more of performance? Substitute two of the engines by turbojets. You will get more thrust for slightly less weight when airbreathing, which will both decrease the time to climb an increase top atmospheric speed. In the end, both things (weight, and rocket takeover speed) will benefit your in-space delta-v. I don't think you really need that much rocket power... I've been toying around with the idea myself of making a RAPIER/turbojet hybrid.

Rune. Won't get you far, but it'll get you there fast.

[Spartwo]

Don't forget 8 tons lighter.What would be the weapon outfit?

*6(and an extra 150m/s d/v)

Best.Kerbal.Ever.

I brute force it because it's military,you have to get there quickly.No point launching if the target already did a few orbits.

Edited February 11, 2014 by Spartwo

[Comrade Jenkens]

I start off with a 45 degree climb until 15,000m and level out until I'm travelling 1700m/s at 26,000m. Then switch to rockets and tilt up 20 degrees.

I'm sure that someone else could pilot it a lot better.

[Spartwo]

I start off with a 45 degree climb until I orbit.

That's me:D

[Comrade Jenkens]

Updated the Condor with the ability to carry a pair of satellites to orbit inside the wings.

Pics updated as well.