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27 minutes ago, RealKerbal3x said:

Those auxiliary radial engines on Lunar Starship got me thinking. They've obviously thought about plume-regolith interaction, so I wonder if those engines will eventually make their way onto the regular Starship design. They'd certainly be beneficial for Mars landing, though they might need a thrust increase as they're probably designed for lunar gravity.

Those aux engines are just hot-gas meth-ox thrusters. Intended for RCS. Pressure-fed. Throttle those up all the way and use nine of them and you have plenty of thrust to land in lunar gravity.

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1 hour ago, sevenperforce said:

Those aux engines are just hot-gas meth-ox thrusters. Intended for RCS. Pressure-fed. Throttle those up all the way and use nine of them and you have plenty of thrust to land in lunar gravity.

Bespoke versions seem plausible as well given how agile construction seems to be.

Up thrusters to 10. Place in 2 rows of 5. Facing what would be the "belly" if it had tiles. Land sideways for cargo delivery out the hinged nose (think C-5 nose).

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13 minutes ago, CatastrophicFailure said:

Well, at least he’s sounding a bit more, er, grounded now...

 

Grounded....I see what you did there.

I assume he means baking propulsively into Earth orbit? Simple enough if you are leaving from an elliptical orbit and returning to one. Assuming an elliptical orbit similar to GTO, that's just 6.82 km/s. Totally doable with a fully-fueled stripped-down starship.

Going from LEO to the lunar surface and back is pushing 11 km/s. Ain't nobody got time for that.

1 hour ago, tater said:

Bespoke versions seem plausible as well given how agile construction seems to be.

Up thrusters to 10. Place in 2 rows of 5. Facing what would be the "belly" if it had tiles. Land sideways for cargo delivery out the hinged nose (think C-5 nose).

I have long been a proponent of horizontal landings on thrusters. They work everywhere except Mars (because Mars needs fully-loaded liftoff). But structural integrity is an issue.

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15 minutes ago, mikegarrison said:

Am I the only one getting Howard Hughes vibes from Elon Musk?

I've been getting them, too. But, as already posted, he's under a little more stress than usual with current and upcoming events, so I'm not worrying yet.

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14 minutes ago, sevenperforce said:

Going from LEO to the lunar surface and back is pushing 11 km/s. Ain't nobody got time for that.

Even the lunar version could aerobrake, just don't go too deep, and make multiple passes.

A stripped down space tanker is basically the depot they discuss in LEO. Looks just like lunar except no crew area, maybe more solar. Launch tanker ferry to LEO. Fill tanker. Either fill a crew vehicle (when so rated for launch) in one go, or alternately, send the depot/tanker to TLI. Tanker partially fills lunar SS at Gateway, reserving very little propellant. Does TEI from Gateway to direct, shallow entry. Scrubs some velocity off, rinse, repeat until it's close to a nominal LEO, reserved props are used to circularize for refill.

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9 minutes ago, tater said:

Even the lunar version could aerobrake, just don't go too deep, and make multiple passes.

A stripped down space tanker is basically the depot they discuss in LEO. Looks just like lunar except no crew area, maybe more solar. Launch tanker ferry to LEO. Fill tanker. Either fill a crew vehicle (when so rated for launch) in one go, or alternately, send the depot/tanker to TLI. Tanker partially fills lunar SS at Gateway, reserving very little propellant. Does TEI from Gateway to direct, shallow entry. Scrubs some velocity off, rinse, repeat until it's close to a nominal LEO, reserved props are used to circularize for refill.

I have suggested that as well but I do not know much about the long-term viability of multi-pass aerobraking. 

14 minutes ago, tater said:

Even the lunar version could aerobrake, just don't go too deep, and make multiple passes.

A stripped down space tanker is basically the depot they discuss in LEO. Looks just like lunar except no crew area, maybe more solar. Launch tanker ferry to LEO. Fill tanker. Either fill a crew vehicle (when so rated for launch) in one go, or alternately, send the depot/tanker to TLI. Tanker partially fills lunar SS at Gateway, reserving very little propellant. Does TEI from Gateway to direct, shallow entry. Scrubs some velocity off, rinse, repeat until it's close to a nominal LEO, reserved props are used to circularize for refill.

I have suggested that as well but I do not know much about the long-term viability of multi-pass aerobraking. 

MRO did it but I don't know of any large spacecraft that has done it at Earth.

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55 minutes ago, sevenperforce said:

MRO did it but I don't know of any large spacecraft that has done it at Earth.

They’ll need to master aerobraking from high energy orbits anyway. Multi-pass is useful for Mars, don’t need to commit to landing as soon as you arrive. I bet they will grill a few SN’s while figuring it out.

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2 minutes ago, sh1pman said:

They’ll need to master aerobraking from high energy orbits anyway. Multi-pass is useful for Mars, don’t need to commit to landing as soon as you arrive. I bet they will grill a few SN’s while figuring it out.

I think it's a different problem, tbh. Aerobraking in deep passes with control surfaces and a heat shield is very very different from aerobraking in a high pass without control surfaces or a heat shield.

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12 hours ago, tater said:
 

Even the lunar version could aerobrake, just don't go too deep, and make multiple passes.

Someone on NSF estimated that without a heat shield, you'd only be able to scrub off one to two meters per second per pass. Translunar injection, as done by Apollo, is a bit over 3 km/s. That works out to 1,500 aerobreaking passes to return to LEO.

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15 hours ago, Wjolcz said:

Or just land the first Mars Starship with a concrete-making robot that builds a pad for the next one. Ok, maybe not on the first one, but I'm pretty sure you get my point.

Standard concrete wouldn't work on Moon, due to water boiling away, but... google time...

I am wrong. Apparently vacuum concrete is a thing:

https://civiltoday.com/civil-engineering-materials/concrete/27-vacuum-concrete-definition-advantages

but... 

Quote

Vacuum concrete stiffens very rapidly so that the form-works can be removed within 30 minutes of casting even on columns of 20 ft. high.

Half an hour of setting time would be too fast. Do we have any concrete specialists here? What cement like vacuum resistant concoction can we pour on Moon to fix the surface?

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3 hours ago, Rakaydos said:

Someone on NSF estimated that without a heat shield, you'd only be able to scrub off one to two meters per second per pass. Translunar injection, as done by Apollo, is a bit over 3 km/s. That works out to 1,500 aerobreaking passes to return to LEO.

That... Doesn't sound right.

Starship can endure very high temperatures even without a heat shield, doesn't have anything flimsy that could be torn off, and almost empty has a high surface area to mass ratio.

Aerobraking should be quite effective for it, intuitively. I'd quite like to see that calculation and its assumptions.

Edited by RCgothic
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3 hours ago, Rakaydos said:

Someone on NSF estimated that without a heat shield, you'd only be able to scrub off one to two meters per second per pass. Translunar injection, as done by Apollo, is a bit over 3 km/s. That works out to 1,500 aerobreaking passes to return to LEO.

If that was true of the no heatshield version, then use the tanker for this. There's gotta be a tanker to Gateway for the lunar ship to ever be reused, anyway.

 

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1 hour ago, tater said:

If that was true of the no heatshield version, then use the tanker for this. There's gotta be a tanker to Gateway for the lunar ship to ever be reused, anyway.

 

That looks...wrong. Like some couples I know.

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50 minutes ago, Flavio hc16 said:

it's just silly:confused::lol:

 

44 minutes ago, sevenperforce said:

That looks...wrong. Like some couples I know.

Yeah, but that's Artemis. Either it docks with Orion, or it docks with Gateway. It will look silly regardless, as Starship is better than anything it docks to that isn't also Starship.

 

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6 hours ago, Shpaget said:

Standard concrete wouldn't work on Moon, due to water boiling away, but... google time...

I am wrong. Apparently vacuum concrete is a thing:

https://civiltoday.com/civil-engineering-materials/concrete/27-vacuum-concrete-definition-advantages

but... 

Half an hour of setting time would be too fast. Do we have any concrete specialists here? What cement like vacuum resistant concoction can we pour on Moon to fix the surface?

Tbh, by 'concrete' I meant anything that's hardened. If compressed regolith works I'm fine with that too.

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3 hours ago, tater said:

If that was true of the no heatshield version, then use the tanker for this. There's gotta be a tanker to Gateway for the lunar ship to ever be reused, anyway.

 

Think starship design was with an docking port in the air lock in the cargo bay. this way it would do double duty as an air lock door for EVA or inspection probes. Nose has the header tank and probably other stuff. 
Yes they probably keep the header tanks, they are nice for matching trajectory with gateway or other stuff. 
On the moon this docking port as an emergency entry if the main cargo hatch failed. Cargo area is designed to be used both pressurized and in vacuum. I assume they will keep it in vacuum on the moon unless you need to repair rovers or other large equipment. 

Now it might make sense to make Moonship a bit shorter, you don't need that large crew compartment for 4-7 crew even with an good lab and lots of bells, whistles and kitchen sinks staying as an mobile moon base for an lunar day. Cargo bay is nice, you want multiple rovers and an drill rig. 
As cargo is lighter you might shorten the tanks for lunar SSTO operation it still need to do any sort of moon missions including polar. 
Now if they use starships to swap crew on this you can go with more crew including tourists so here the large crew quarters makes sense. 

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47 minutes ago, magnemoe said:

Think starship design was with an docking port in the air lock in the cargo bay. this way it would do double duty as an air lock door for EVA or inspection probes. Nose has the header tank and probably other stuff. 

it won't need the header tank as it won't do the bellyflop

47 minutes ago, magnemoe said:


Yes they probably keep the header tanks, they are nice for matching trajectory with gateway or other stuff. 

hmmm, you need just rcs to slosh the fuel around, and the header tank might go into the main tanks

 

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