Eve SSTO is impossible!

[problemecium]

Have we tried this?

[GoSlash27]

paramecium,

infinite fuel would be cheating. Any setup can make SSTO with infinite fuel.

Best,

-Slashy

[Master Tao]

paramecium,

infinite fuel would be cheating. Any setup can make SSTO with infinite fuel.

Best,

-Slashy

I think the point was that you can now have infinite thrust without debug cheats since the OMS engines are physicsless. You should just have to cram in enough monopropellant and engines – more than I have the patience to try on my laptop.

[GoSlash27]

I think the point was that you can now have infinite thrust without debug cheats since the OMS engines are physicsless. You should just have to cram in enough monopropellant and engines – more than I have the patience to try on my laptop.

Unfortunately, it doesn't quite work like that. Your engines have no mass, but your tanks do. Knowing that your most mass- efficient propellant tank has a hard limit for wet to dry ratio of 8.5 allows you to mathematically derive an absolute upper bound for DV. It works out to the numbers I posted above; 4,619 M/sec atmospheric and 6,090 M/sec vacuum. Adding engines and tanks will never exceed these limits no matter what you do.

Regards,

-Slashy

Edited August 1, 2014 by GoSlash27

[Doge]

Everyone is over thinking it! All you have to do is add more boosters until you have a rocket with such ridiculous TWR that you can get into Eve orbit on minimum thrust. The only problem is that no one's computer could handle it.

[Red Iron Crown]

Everyone is over thinking it! All you have to do is add more boosters until you have a rocket with such ridiculous TWR that you can get into Eve orbit on minimum thrust. The only problem is that no one's computer could handle it.

That approach is eliminated mathematically. Adding an infinite number of boosters would not get to orbit in a single stage.

[impwarhamer]

That approach is eliminated mathematically. Adding an infinite number of boosters would not get to orbit in a single stage.

I still wonder about that though. What if you had a rocket bigger than the planet itself? (assuming the rocket has no gravitational effect on the planet)

[GoSlash27]

I still wonder about that though. What if you had a rocket bigger than the planet itself? (assuming the rocket has no gravitational effect on the planet)

The same limits would still apply. Regardless of what your ship's mass is, you still need a known DV to attain orbit. Unless they make a fuel tank massless or dramatically improve the wet/ dry ratio, Eve SSTO will remain impossible. OTOH, if they ever do make a "massless" fuel tank, then pretty much anything is possible.

Best,

-Slashy

Edited August 1, 2014 by GoSlash27

[Red Iron Crown]

I still wonder about that though. What if you had a rocket bigger than the planet itself? (assuming the rocket has no gravitational effect on the planet)

Still impossible.

Assume the rocket is all engine and tank, not even a probe core, but is still functional. Let's compare a couple of the best engines in terms of TWR and dV possible on Eve, and assume we only need a 1.0 TWR to begin the ascent:

LV-N: Mass 2.25, Thrust 60, Isp 800. A single LV-N can lift 3.6 tons of fuel on Eve, which gives only 6220m/s of dV even at its highly efficient vacuum Isp.

KR-2L: Mass: 6.5, Thrust 2500, Isp 380. A single KR-2L can lift 143.1 tons of fuel on Eve, which gives only 7085 m/s of dV.

These are the theoretical limits for those engines in a single stage on Eve and cannot be achieved if carrying any payload. They can only be approached, no matter how many boosters are added.

Though we hardly had to check the KR-2L, no chemical engine powered single stage can reach the theoretical limit of 8415m/s even if TWR is ignored. (And that is in vacuum, the situation is worse in atmosphere which Eve has in abundance).

It requires approximately 8500m/s to reach low Eve orbit from the highest mountain peak.

So there is no combination of rocket engines and fuel tanks that can reach orbit in a single stage from Eve's surface in a conventional rocket.

[Master Tao]

Knowing that your most mass- efficient propellant tank has a hard limit for wet to dry ratio of 8.5 allows you to mathematically derive an absolute upper bound for DV.

Thanks – it's been so long since I've worked the rocket equation by hand that I'd forgotten about that limit.

[TheKutKu]

Does a Gyroplane Eve SSTO (it's possible) count? Or is it classed as an infinigliding?

Edited August 1, 2014 by TheKutKu

[GoSlash27]

Does a Gyroplane Eve SSTO (it's possible) count? Or is it classed as an infinigliding?

That one would certainly count as infinigliding due to all the control surfaces, but yeah. Gyroplanes are effectively perpetual motion machines in KSP so I'd count it as taking advantage of a loophole in the physics.

Still... if you can build one that works, I'm sure we'd all like to see it in action.

Best,

-Slashy

[Taquarinha]

There is no loophole in physics, the only thing is that SAS modules in KSP are Ridiculously powerfull for their mass.

[thereaverofdarkness]

I don't think it's mathematically possible. You need to scrounge up 9km/s of delta-v or more, while maintaining a TWR of at least 1 on Eve. I don't think any combination of stock parts can do that in 1 stage. My only theory on how you might be able to do it is some sort of ion powered glider, but I don't think it's possible to make the transition from lift based flight to the orbital regime with just ion power.

I succeeded with this handily completely stock design and flying it by myself to EVE with no assistance in any way from mods. I got it just above the ground and gently touched it down at under 1m/s--at which point I discovered it wasn't sturdy enough to hold its weight in the gravity. (This was built in early 0.22 but took till late 0.23 to deploy to EVE due to Kraken effects in the craft) I was still able to parachute the craft to a few meters above the surface (near shore, so under 100m altitude) and then ignite engines and take off at the same time as I ditched the parachutes. I had been unable to completely fuel the craft due to kraken effects so its first stage was just over half full, but I brought enough extra Dv that it was alright. At the end I was near to exiting the atmosphere with one stage remaining but was unable to control the craft due to a powerful Kraken spin.

I never figured out why the craft was acquiring so much phantom force or how to make it stop, but I can only assume the great Kraken did not wish me to succeed in my plan. But I see no reason to believe that with proper construction, a craft could use basically the same design as mine and have no trouble landing on low ground on EVE and take off into orbit. Oh and mine had a Mark 1 pod, not a probe core or EAS chair. I didn't think much about gravity because the way I tested my craft initially was to launch it into orbit around Kerbin, land it, and launch it back into orbit again. That ensured I had at least 9000 dV (without any calculations), and I used engines that could handle the thick atmosphere: mainsails and aerospikes primarily.

Anyway, even though I didn't fully succeed due to phantom force bugs and lack of ability to test gravity on Kerbin, the large excess of dV I had even from a low altitude launch says a lot about the capabilities there. Now with the 2.5m quad couplers, I could probably make an even smaller one with only aerospikes that could launch from EVE's surface and also be capable of landing on it. The biggest problem with my first design was that it was overbuilt, not that it was underbuilt.

Also Scott Manley did it with stock parts and his launch vehicle was also a rover. So it's quite possible.

Edited August 2, 2014 by thereaverofdarkness

[GoSlash27]

I would need to see some sort of evidence to back this up. Do you have a link to the Manley vehicle? What about a craft file for yours?

*edit* wait... did you say "stage"?

We're talkin' about SSTO, not multistage vehicles.

Edited August 2, 2014 by GoSlash27

[thereaverofdarkness]

I would need to see some sort of evidence to back this up. Do you have a link to the Manley vehicle? What about a craft file for yours?

*edit* wait... did you say "stage"?

We're talkin' about SSTO, not multistage vehicles.

oh whoops, I totally missed this.

[GoSlash27]

oh whoops, I totally missed this.

'Sallright. Happens to all of us from time to time...

-Slashy

[goduranus]

That one would certainly count as infinigliding due to all the control surfaces, but yeah. Gyroplanes are effectively perpetual motion machines in KSP so I'd count it as taking advantage of a loophole in the physics.

It's like a nuclear powered helicopter, with reaction wheels standing in for a helicopter drive system not in the game. Combining an air breathing nuclear propulsion(though not necessarily in helicopter form) with a nuclear rocket is probably a reasonable way of building a SSTO that launch from more extreme atmospheres.

[GoSlash27]

It's like a nuclear powered helicopter, with reaction wheels standing in for a helicopter drive system not in the game. Combining an air breathing nuclear propulsion(though not necessarily in helicopter form) with a nuclear rocket is probably a reasonable way of building a SSTO that launch from more extreme atmospheres.

Sorry, no can do. But this does give me an idea for a new challenge; one where 'copters would be okay...

-Slashy

[TheKutKu]

I'm working on a helicopter Eve ssto. I climb up to 25000 M and then i activate the nuclear engine.

[CavemanNinja]

I'm actually trying this currently using helicopters, which use smaller engines to gain more height than normally possible.

As a point of clarification, helicopters powered by sas or ASAS are out, correct?

Edited August 3, 2014 by CavemanNinja

[TheKutKu]

@CavemanNinja, i have tried, engine-powered helicopters are Less efficient than a rocket with the same engine.

one of my helicopter with 100 rcs and 4 rcs engine goes to 500 M, whereas a rocket with 100 rcs , the same mass and the same engine goes to 6000 M

Edited August 3, 2014 by TheKutKu
Oops, i wrote 600M

[GoSlash27]

I'm actually trying this currently using helicopters, which use smaller engines to gain more height than normally possible.

As a point of clarification, helicopters powered by sas or ASAS are out, correct?

Affirmative.

Best,

-Slashy

[thereaverofdarkness]

This could be done with balloons.

Perhaps a more reasonable challenge would allow dropping weight off, but you only get one set of engines to work with. That might end up being too easy though.

or............howabout the ONLY mass you can release is engines? All spent fuel tanks must stay but if you can drop engines you lose power but you lose a bit of mass too. That might keep it difficult but make it doable!

[James_Eh]

Just so I'm absolutely clear here, because I've been fooling around on Kerbin with interesting results:

- slap a skipper onto an orange tank (plus the minimum other stuff) and you have something with 5300 dV and plenty of thrust to reach orbit

- slap a pair of LV'Ns onto an orange tank and you have something with 12000 dV and enough thrust to slightly cushion the blow as you fall from the launch clamps to the pad

- slap all 3 on, and let them all run, and you run out of fuel before reaching orbit (if you just activate the LV-Ns you have 9740 dV but again not remotely enough thrust to go anywhere but down into the irradiated ground)

- however: slap all 3 on and manually reduce the skipper's thrust as you head up, so that you maximize the amount of contribution by the 800 ISP LV-Ns, and you wind up in orbit with a pile of dV left

By continuously shifting downwards the contribution of the less efficient engines to the ascent, and ultimately running from just LV-Ns (a much larger setup than the above would be required), could you pull it off? From a practical point of view I have no idea how you would throttle down a pile of engines one by one without spinning out of control...

Or is this approach negated by the pure math discussion above?

Edited August 3, 2014 by James_Eh
clarify point 3