Eve SSTOs

[The_Rocketeer]

Have you ever tried an Eve SSTO ascent? Did you succeed? If not, what went wrong? Was there an unknown hurdle, or was it just a case of time/effort?

Today I've been testing some designs with a view to completing my first ever Eve surface return - as I type I'm actually taking a break from the frustrations of CTD and HyperEdit (if I was even slightly more confident of success I'd skip the HyperEdit part and just fly there... ) but however. The first and only time I made a trip to Eve (not counting fly-bys) was long ago when I first built an orbit-capable nuke-powered spaceplane, and having refuelled it at my orbital station, needed somewhere to send it. Suffice to say the pilot, Thornberry, still lives alone in Thornberryland . He has a beard and his only friend is a blown lightbulb, called Dave.

I digress.

Seeing as getting to the ground is easy(er) and coming up again is much harder, and generally not liking to do anything by halves, I've decided my ascent vehicle needs to be a bit more than a Mk1 Pod on top of a massive asparagusboostermobile. It needs plenty of seats, for all those poor stranded kerbs who may never get another chance to go home, a docking port for refuelling in orbit, and a cargo bay for all the snacks and other useful stuff needed for such a long journey. Maybe even a rover or a tow-vehicle for helping position the vessel for eventual take-off, or a science lab. Anyway, the general idea is stuff in the bay is payload to the surface, so it isn't part of the ascent vehicle.

Up until my current design revision, I was working with Mammoth and Nerva combinations. On Kerbin this put me into a nice high orbit, but on Eve I just wasn't in space long enough to get up to orbital velocity once the oxidiser ran out. The new design ditched the Nervas for an extra Mammoth, and this looks extremely promising. I've just had enough of CTDs and HyperEdit....!

[TheBrisbyMouse]

I wish you good luck in this endeavor.

I've yet to leave Eve's gaping maw, let alone do it in one stage.

[Starhawk]

I am aware of only one successful SSTO from Eve's surface, by astrobond IIRC. That was done by hyperediting the craft to the top of a high mountain.

To the best of my knowledge, landing and return from surface SSTO has not yet been achieved.

Happy landings!

[Red Iron Crown]

Obligatory link to astrobond's successful stock Eve SSTO for those who haven't seen it: http://forum.kerbalspaceprogram.com/threads/132211-Eve-SSTO-Limbo?p=2167429&viewfull=1#post2167429

Edit: Ninjahawked!

[The_Rocketeer]

Well, so much for the theory that landing would be simple. I'm fairly certain I have the correct proportions of TWR, dV, lift and drag, but I haven't even managed to test an ascent yet because the craft refuses to glide to a landing nose-first - those mammoths and all that fuel make for one heavy tail. I'm going to have to spend some more time tinkering in the SPH until I find a nice stable airframe.

I'm already finding there are many more elements to this objective than I'd anticipated, but luckily I'm a pugnacious sod!

[Red Dwarf]

Well, so much for the theory that landing would be simple. I'm fairly certain I have the correct proportions of TWR, dV, lift and drag, but I haven't even managed to test an ascent yet because the craft refuses to glide to a landing nose-first - those mammoths and all that fuel make for one heavy tail. I'm going to have to spend some more time tinkering in the SPH until I find a nice stable airframe.

I'm already finding there are many more elements to this objective than I'd anticipated, but luckily I'm a pugnacious sod!

I figured the way to do it was land it empty with a refinery attached, or have infrastructure already in place to refuel the craft. I'm planning my own mission to Eve (won't be able to do it till I get back from school, major bummer), and that's how it's gonna work. Large-ish rocket, refueling rig, base, and biome-hopper rocket plane to get around. I'm really pumped for the mini-ISRU that's coming out in 1.0.5. It's gonna make that whole plan a lot more feasible!

[Dark Junior]

When I attemptet it (I just built stuff and hyperedited them directly to eve.) I just went up REALLY fast and tried to ecape Eve, I succeeded. Afterwards, I tried to land on kerbin, and I went to duna instead. Agter trying to fix my course, I had almost no fuel left. I hit duna. HARD.

[The_Rocketeer]

I figured the way to do it was land it empty with a refinery attached, or have infrastructure already in place to refuel the craft.

That is one option, but I'm too impatient to wait for a mining rig to fill up the ~40k LF+O to brim the tanks, especially when I'm just 'simulating'. It should be possible to land fully loaded as long as the craft is draggy at the back and heavy at the front. One design concept I'm evaluating shifts 2 of the Mammoths to nose- or waist-mounted nacelles, which makes a big difference to the weight distribution.

When I attemptet it (I just built stuff and hyperedited them directly to eve.) I just went up REALLY fast and tried to ecape Eve, I succeeded. Afterwards, I tried to land on kerbin, and I went to duna instead. Agter trying to fix my course, I had almost no fuel left. I hit duna. HARD.

Haha, oops. During a Kerbin test I was juggling fuel around various tanks and by the time I figured I'd better save what was left for circularising I'd already escaped Kerbin and lowered my sun periapsis to well inside Eve's orbit. This is one of the reasons I'm optimistic about reaching orbit with my current spec, tho the configuration could stand some improvement to iron out the glide stability issue. I think part of the problem is excessive nose-drag (I'm using a Mk3 cockpit on the centre fuselage), so I'm going to experiment with fairings too.

[Red Dwarf]

That is one option, but I'm too impatient to wait for a mining rig to fill up the ~40k LF+O to brim the tanks, especially when I'm just 'simulating'. It should be possible to land fully loaded as long as the craft is draggy at the back and heavy at the front. One design concept I'm evaluating shifts 2 of the Mammoths to nose- or waist-mounted nacelles, which makes a big difference to the weight distribution.

Haha, oops. During a Kerbin test I was juggling fuel around various tanks and by the time I figured I'd better save what was left for circularising I'd already escaped Kerbin and lowered my sun periapsis to well inside Eve's orbit. This is one of the reasons I'm optimistic about reaching orbit with my current spec, tho the configuration could stand some improvement to iron out the glide stability issue. I think part of the problem is excessive nose-drag (I'm using a Mk3 cockpit on the centre fuselage), so I'm going to experiment with fairings too.

Really, I was more considering the refueling method to save on launch costs and part counts. Launching an Eve rocket fully fueled from Kerbin takes waaaay more than an empty Eve rocket and an attached refinery. The launch vehicle will still be pretty hefty, but a whole heck of a lot less than the alternative. The ascent really isn't affected by whether the fuel was brought with or made on-sight. If it's an SSTO, it might have more of an effect on the design.

[The_Rocketeer]

Last design I noticed had about 80 parts, of which about 20 were airbrakes and about 10 more were a series of tapering parts for the nacelle noses.

An SSTO for Eve can ascend and refuel from Kerbin, transfer to Eve and refuel from Gilly before descent. Yeh, it could take down an ISRU/drill in the cargo bay, but I'd rather use that for a rover and/or lab. Either way the refinery/payload would get left behind. If the machine needs a disposable refinery to complete the mission, I don't really class that as an SSTO.

Update:

Tested ascent today from about 7000m altitude (borrowing Astrobond's launch site), ran out of fuel ~600m/s short of a 100km orbit. On the other hand, the craft seems to fly much better since I modified the wingplan, next iteration needs more vertical fin for glide stability.

I'm confident I could reach orbit with this power-unit if I reduced the utility parts to a single cockpit, since that would save me about 15t of deadweight, but I lump that together with the idea of using disposable boosters - it wouldn't be the goal I've set.

New Update:

Cripes, that last 600m/s is kicking my butt. I guess those who've had a real go at Eve ascents before probably had a little giggle when I said it. I've tried a lot of different things, but I have a sinking feeling that my non-thrusting mass is just too high. Which blows, because at the moment this feels real close to being really impressive! I guess I could try finding an even higher launch point, but the ship is so heavy that it takes a really long roll to get up to lifting speed, and finding mountain tops that big and flat is tough. There can't be that many of them over 7km either.

Edited October 21, 2015 by The_Rocketeer

[AeroGav]

Something I feel is missing from the stock parts are air breathing nuclear engines. I'm a relative newbie and unwilling to take the easy technobabble solution to problems, but i don't see why a version of the LV-N that can also use intake air would be beyond Kerbin technology. It would need a turbine compression stage to compress the intake air, and a power turbine in the exhaust stream to drive that. As a result, it would be subject to the same decline in thrust with speed and altitude as a turboramjet - the Rapier engine chills the intake air with the fuel stream before it enters the combustion chambers, which enables it to operate faster and higher, unfortunately a nuclear turboramjet won't have that. You could also swap the nozzle for an aerospike. The stock LV-N performs well in a vacuum, but suffers more thrust loss due to atmosphere than any other rocket - a factor of 6 or something crazy like that. Aerospikes are not quite as good in a vacuum, but perform a hell of a lot better at surface pressure. They are also much less draggy.

All in all, such an engine will not do much more than allow indefinite level flight at low altitude , due to low TWR , 1950s nuclear powered aircraft concepts still required jet engines to get off the runway. But at least your LVN's aren't total passengers below 20k, or wasting fuel unnecessarily.

Taking things one step further, liquid core nuclear engines. Technologically, I don't see any reason why we couldn't build one now, but you could never use such a thing on earth due to the intensely radioactive exhaust. Should have around three times the TWR and ISP of the solid core nuclear thermal engine however.

[CrashTestDanny]

Well, so much for the theory that landing would be simple. I'm fairly certain I have the correct proportions of TWR, dV, lift and drag, but I haven't even managed to test an ascent yet because the craft refuses to glide to a landing nose-first - those mammoths and all that fuel make for one heavy tail. I'm going to have to spend some more time tinkering in the SPH until I find a nice stable airframe.

I'm already finding there are many more elements to this objective than I'd anticipated, but luckily I'm a pugnacious sod!

If you check the pics of Astrobond's ascent, you'll notice that he locks off the forward tanks to force the aft ones to burn first, keeping the CG forward. I recreated his craft in my laboratory and then rearranged the wings so I didn't have to do that and I was able to successfully glide to the surface. I have not been as successful with the ascent yet (craft was too nose heavy and could not rotate), but I am convinced that he has a formula that will work for EVE SSTO - just got to get the placement of CG, CL, and main gears right.

Danny

[Foxster]

I suggest holding on for a few more days before spending too much time on this. 1.0.5 is supposed to have some atmosphere tweaks that will allow aerobraking at Eve again and this will almost certainly change the dV orbit requirements too.

It could be that the atmosphere will thin quicker and that could mean a little less dV being required for orbit. It only needs a little less to make SSTOs viable.