Hello there all!
I was exploring the ‘Records’ sub-forum and I came across this little gem of a challenge posted by EmberSkyMedia :
“Largest SSTO to land on Mars (with Return)
Largest SSTO to land on Venus (with Return)
The whole craft must return (minus fuel + used parachutes of course).
Score: Dry-Mass on return (so zero out your fuel before you do craft recovery).”
No refueling allowed.
It was an interesting idea, but then a reply by Space_geek25 got me thinking:
“I think it's impossible to land on mars/venus and back with an SSTO with no refueling. You need 3000m/s of Dv for reaching LEO, 2×900 for space travel and 2000 to reach LxO. It make approximately 6800m/s of Dv, so the rapport between wet and dry mass must be >12, or the maximum is 10. ( I supposed ISP=280 so it's even harder with Hawk or kolibri engines)with ions it must be possible but they are cheated.”
Then, add Mooncrasher ’s rule of “no modded engines for that kind of return record.
”, plus not allowing any engine stretching, and…
CHALLENGE ACCEPTED!!!
*Note: I did allow bp-editing, and no-heat settings on stacked engines to optimize functionality and mass, but only because I found it was impossible to do otherwise. However, there were no delta-v cheats, fuel% hacks, or other cheats used.
The first thing I had to determine was the maximum delta-V of an SSTO with a starting TWR of at least 1.10, using only standard engines. Choosing layered Frontier engines was an easy first step for their high isp and thrust combination.
The advantage-curve for the number of engines goes flat quickly after about 15, because of the increasing empty tank & engine mass you have to lug around, so ultimately, I settled on 12 engines. 12 lets you be powerful enough to carry the fuel and parachutes for a mars return, while keeping the craft light enough that parachutes aren't useless in descents.
Even with part modifications to ensure an ultralight rocket, and using every aerobraking opportunity we can, we can just barely meet the delta-V required.
( ~2875 m/s for reaching LEO )
( ~740 m/s for Mars Transfer)
( a smidge for Mars Landing Deceleration )
( ~920 m/s for reaching LMO )
( ~440 m/s for Earth Return Transfer )
( a smidge more for Earth Touchdown )
After five iterations, I came up with one final craft that checked all the boxes and could make the full trip-
Here’s the full mission, and yes I do still feel guilty about putting a heat shield under the engines, but it couldn't seem to work around it with the other constraints and it’s functional and looks half descent so yea
The final mass, as required in the original record-challenge, would then be 175.46t after emptying the tanks back on Earth.
It can also be used as a normal SSTO to launch a max payload of 220t into LEO! Just drain the top two riveted tanks and attach the payload adapter/ballast included in the bp.
BP-
MR SSTO v5.zip
I’ll post the final build delta-V specs if anyone asks, but until then,
Cheers
I was exploring the ‘Records’ sub-forum and I came across this little gem of a challenge posted by EmberSkyMedia :
“Largest SSTO to land on Mars (with Return)
Largest SSTO to land on Venus (with Return)
The whole craft must return (minus fuel + used parachutes of course).
Score: Dry-Mass on return (so zero out your fuel before you do craft recovery).”
No refueling allowed.
It was an interesting idea, but then a reply by Space_geek25 got me thinking:
“I think it's impossible to land on mars/venus and back with an SSTO with no refueling. You need 3000m/s of Dv for reaching LEO, 2×900 for space travel and 2000 to reach LxO. It make approximately 6800m/s of Dv, so the rapport between wet and dry mass must be >12, or the maximum is 10. ( I supposed ISP=280 so it's even harder with Hawk or kolibri engines)with ions it must be possible but they are cheated.”
Then, add Mooncrasher ’s rule of “no modded engines for that kind of return record.
”, plus not allowing any engine stretching, and…CHALLENGE ACCEPTED!!!
*Note: I did allow bp-editing, and no-heat settings on stacked engines to optimize functionality and mass, but only because I found it was impossible to do otherwise. However, there were no delta-v cheats, fuel% hacks, or other cheats used.
The first thing I had to determine was the maximum delta-V of an SSTO with a starting TWR of at least 1.10, using only standard engines. Choosing layered Frontier engines was an easy first step for their high isp and thrust combination.
The advantage-curve for the number of engines goes flat quickly after about 15, because of the increasing empty tank & engine mass you have to lug around, so ultimately, I settled on 12 engines. 12 lets you be powerful enough to carry the fuel and parachutes for a mars return, while keeping the craft light enough that parachutes aren't useless in descents.
Even with part modifications to ensure an ultralight rocket, and using every aerobraking opportunity we can, we can just barely meet the delta-V required.
( ~2875 m/s for reaching LEO )
( ~740 m/s for Mars Transfer)
( a smidge for Mars Landing Deceleration )
( ~920 m/s for reaching LMO )
( ~440 m/s for Earth Return Transfer )
( a smidge more for Earth Touchdown )
After five iterations, I came up with one final craft that checked all the boxes and could make the full trip-
the Mars Return - SSTO by Proxima, v.5
“MR-SSTOP5”
“MR-SSTOP5”
(or “Mr. Stops” for fun)
Here’s the full mission, and yes I do still feel guilty about putting a heat shield under the engines, but it couldn't seem to work around it with the other constraints and it’s functional and looks half descent so yea
The final mass, as required in the original record-challenge, would then be 175.46t after emptying the tanks back on Earth.
It can also be used as a normal SSTO to launch a max payload of 220t into LEO! Just drain the top two riveted tanks and attach the payload adapter/ballast included in the bp.
BP-
MR SSTO v5.zip
I’ll post the final build delta-V specs if anyone asks, but until then,
Cheers
