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Getting an SSTO to Eeloo when it is at or near apoapsis without gravity assists

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the way it is worded, it would mean that i can make an ssto, then once in orbit ditch stages. which would be easy, it's just a matter of an ssto with an eeloo rocket as payload.

then again, the other interpretation - no stages whatsoever - would be exceedingly difficult, as it would require some 8000 m/s in a single stage. though most of it can be provided by ions, so it should be feasible

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27 minutes ago, Bej Kerman said:

Does not compute

as ssto goes to orbit in a single stage. nothing then says it cannot use stages after it's gone to orbit.

my donkey launcher is an ssto for 25 tons in LKO. it drops the payload, then deorbits and gets recovered. so, it i send the donkey with a 25 ton probe in orbit, then deorbit the donkey and make an eeloo mission with that probe, i have made the mission with the ssto.

or would i have to bring the whole donkey launcher to eeloo?

how about landing? if i orbit eeloo and then detach a lander, the lander lands and orbits again, rejoins the orbiter, then goes back to kerbin, does that still count as ssto?

and what about isru? if isru is allowed, then the objective really becomes "bring an ssto with a convert-o-tron to minmus", because once you start refueling, you can go anywhere.

the challenge needs to be defined better

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I guess I was pretty vague, so I'll just say it here. I meant Single Stage to Eeloo, I guess you could say.

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This is a fun challenge with plenty of potential! A single stage vessel to Eeloo at periapsis needs about 4,500 to 5,000 m/s from LKO. High but not impossible for an efficient design.

The obvious choice of ion engines is feasible but has some drawbacks. Solar power is basically non-existent at Eeloo's apoapsis and Eeloo's gravity is high enough to make landing on the low TWR of ions alone challenging. Best bring some alternate power source and some extra landing engines.

A Rapier/Nuke combo would also be quite effective and probably simpler to execute the journey.

To get the ball rolling here's an entry applying the strictest interpretation of the rules. Single stage from Kerbin to Eeloo's surface without any refueling. A fuel cell tucked away in a non-stageable fairing provides enough power to run 2 ion engines consistently.

Just enough fuel to make it to the surface intact! I'm sure that the creative and ingenious folks on this forum can come up with plenty of other approaches. :)


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@Nicodo123 You could consider tweaking the challenge to attract some healthy competition. For example you could split entries into ranks, here's one idea:

Gold: Kerbin to surface of Eeloo and back to Kerbin without any refuelling whatsover.
Silver: Kerbin to surface of Eeloo without refuelling along the way.
Bronze: Kerbin to surface of Eeloo with a pit stop.

Alternatively, ranking by cost / mass / part count are also popular options.

Edited by ManEatingApe
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The gravity assist restriction makes this a lot more difficult. Maybe I'll try this without ion engines later today. Also fuel cells aren't the best option to power ion engines since it reduces the effective isp to somewhere around 1600. RTGs or a big battery pack are better

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This craft's a bit heavier than ManEatingApe's submission because I didn't use any ions and I also do a return.


On runway


Nuke turns on at 1500m/s and I point prograde the rest of the way to orbit


In orbit with a lot of delta-v remaining. This craft could probably be good for an orbital relay race also, it could do at least six orbits by itself.


Periapsis kick burns


Large escape burn. This is higher than normal because I want to do a bi-elliptic transfer to Eeloo, to save fuel.


Intercept burn


Eeloo orbit








In orbit


kerbin transfer


Aerobraking. The kerbal is shielded by the air intake



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On 3/1/2021 at 7:27 PM, Nicodo123 said:

I guess I was pretty vague, so I'll just say it here. I meant Single Stage to Eeloo, I guess you could say.

Challenge accepted.


In fact, I managed to pull it off a year ago finishing a tourism contract. If you want more details, look up my forum posts about the Raven-Remembrance Saga - otherwise known as the Remembrance-Trainwreck Saga

  • The forum post announcing the Eeloo landing, made February 2020




If you want more details on how I carried out this mission, I started with a Minmus landing to refuel after taking off. However, the details on what happened after that are a bit fuzzy. More specifically, I don't remember if I:

  • Went straight to Eeloo after refueling on Minmus (most likely), or made a pit stop at Ike
  • Blasted off back to Kerbin with or without an ore transport between Eeloo takeoff and the exit burn.


Either way, I am certain on the outcome and the main gist:

  1. The Poseidon SSTO took off from Kerbin
  2. Said SSTO did not use gravity assists to reach Eeloo, then landed on the surface to refuel
  3. That SSTO flew back to Kerbin, landing on 0-9 KSC in one piece.
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