Author Topic: Moon Starship  (Read 739471 times)

Offline raketa

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Moon Starship
« on: 09/30/2019 01:45 am »
1/Refueling Starship on elliptical orbit sounds to me too clumsy.
2/Moon starship could have small modification, tanks stretch by 10-20%.
3/Cargo/Crew space will be  a little bit squeeze, but for short trip to Moon could be OK.
4/SS will be filled just 80%-90% of stretch tanks, on launch pad.
5/SS will be completely refuel on LEO.
6/It will align logistic of refueling with Mars mission.

See also this thread which discusses the actual Artemis annoucement, SpaceX starship was selected as a candidate lander:  https://forum.nasaspaceflight.com/index.php?topic=50806
« Last Edit: 04/30/2020 06:40 pm by Lar »

Offline Lemurion

Re: Moon Starship
« Reply #1 on: 09/30/2019 02:04 am »
The problem I see is that you’re trading operational complexity for design complexity and I don’t think SpaceX wants to make that trade off. Developing a different Starship version for Lunar flights sounds like a lot more of a hassle for SpaceX than refueling in an elliptical orbit.

It also goes against Elon’s design principles.

Offline sevenperforce

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Re: Moon Starship
« Reply #2 on: 09/30/2019 12:27 pm »
I am confident we would not see a tank stretch for a lunar mission. What we might see, conceivably, is a version of Starship without wings or a heat shield, with wider landing legs, initially launched unmanned, to act as lunar surface shuttle. It would be substantially lighter and (without doing the math) could probably manage to go from fully-fueled in LEO to a lunar landing and back up to LLO.

Then, standard Starships could be used to ferry crew between LEO and LLO, and tankers could be used to refuel the lunar Starship in LLO.

Trouble with this is that it doesn't allow the Raptors to be serviced or inspected on Earth, which is an essential part of reuse. It also presents challenges for cargo delivery. You would have to transport your cargo out of the standard Starship and into the lunar Starship in LLO, in zero gravity. It's doable, for sure, but it's not easy. There's a big advantage in being able to design and implement a cargo deployment apporach on Earth that you lose if you are doing in-space cargo transfers.

The other trouble is the very problem with Gateway, because LLO is simply not a good place for staging due to mascons, Earth return timing, and the desire for polar access.

Online Eer

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Re: Moon Starship
« Reply #3 on: 09/30/2019 12:54 pm »

Then, standard Starships could be used to ferry crew between LEO and LLO, and tankers could be used to refuel the lunar Starship in LLO.

Trouble with this is that it doesn't allow the Raptors to be serviced or inspected on Earth, which is an essential part of reuse. It also presents challenges for cargo delivery. You would have to transport your cargo out of the standard Starship and into the lunar Starship in LLO, in zero gravity. It's doable, for sure, but it's not easy.
While there are disadvantages, I suspect the counter argument will be that other advantages will prevail. Cross docking distribution centers make good use of industry standard shipping containers and cargo handling. Same can apply to routine high volume high frequency transport through a gateway or similar.  See discussion elsewhere here on the forum on standardized cargo containers.  Edit:  see https://forum.nasaspaceflight.com/index.php?topic=40454.0
Quote
The other trouble is the very problem with Gateway, because LLO is simply not a good place for staging due to mascons, Earth return timing, and the desire for polar access.
Location, location, location. It may take a while to understand the best place to put the first cross dock distribution center, but that will become clear when the destination is decided.

I like the idea for multiple reasons. A small fleet of space only “last mile” delivery trucks makes sense, and those done need heat shields and 1G landing legs.  Cross dock is a design pattern that is known to work in many shipping situations. And localized repair and maintenance facilities are inevitable anyway. Roadside repair shops the size of a Starship should make an interesting niche market for someone.
« Last Edit: 09/30/2019 01:02 pm by Eer »
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Offline envy887

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Re: Moon Starship
« Reply #4 on: 09/30/2019 02:12 pm »
Refueling in LLO on the return journey eliminates the need for hardware modifications like tank stretches, and has much greater benefit for landed payload.

Aerobraking into LEO and taking on landing fuel there also helps; there's no need to send landing fuel all the way to LLO or worse, all the way to the lunar surface.

Or, using big dewars of LOX/LCH4 in the cargo bay could do the same thing as a tank stretch, but without modifying the basic ship design and has the added advantage of reducing boiloff to near-zero.

With LLO and LEO refueling I'm calculating a landed payload of 50 t and return payload of 30 t, at a total of 11 launches per landing. That's 4.6 t of landed payload per launch, which is about the same as Apollo - but every stitch of hardware comes home for reuse, and 90% of it only goes to LEO at most.
« Last Edit: 09/30/2019 02:14 pm by envy887 »

Offline corneliussulla

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Re: Moon Starship
« Reply #5 on: 09/30/2019 02:31 pm »
it seems to me landing SS on the moon is very wasteful. You are taking 120 tonnes plus fuel down to surface and back up again. Wouldnt cargo transfer in LLO to moon landers be a less wasteful solution. They could standardise container for loading onto the lunar lander, the lunar landers could also be refueled from the SS and delivered to LLO by the SS.

for instance the ARES programme Altair was designed to deliver about 14-15 tonnes of cargo to the moon surface and had a total weight when fueled and loaded of about 45 tonnes. Having said that if SS can refuel as easily as Elon suggests maybe it makes no sense to make another vehicle. After all if Lockheed got its hands on a lunar lander contract we could be looking at 10 years and $15 bill just to develop it, Meanwhile SS will have colonised the inner solar system LOL
« Last Edit: 09/30/2019 02:32 pm by corneliussulla »

Offline envy887

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Re: Moon Starship
« Reply #6 on: 09/30/2019 02:34 pm »
it seems to me landing SS on the moon is very wasteful. You are taking 120 tonnes plus fuel down to surface and back up again. Wouldnt cargo transfer in LLO to moon landers be a less wasteful solution. They could standardise container for loading onto the lunar lander, the lunar landers could also be refueled from the SS and delivered to LLO by the SS.

for instance the ARES programme Altair was designed to deliver about 14-15 tonnes of cargo to the moon surface and had a total weight when fueled and loaded of about 45 tonnes. Having said that if SS can refuel as easily as Elon suggests maybe it makes no sense to make another vehicle. After all if Lockheed got its hands on a lunar lander contract we could be looking at 10 years and $15 bill just to develop it, Meanwhile SS will have colonised the inner solar system LOL

Starship can stage fuel in LLO, which makes it far more efficient than LEO direct to surface.

Whether you want a dedicated lander mainly depends on how expensive it is to get fuel to LEO vs. the cost of maintaining a lander on the lunar surface.

Offline gefere

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Re: Moon Starship
« Reply #7 on: 09/30/2019 02:58 pm »

Then, standard Starships could be used to ferry crew between LEO and LLO, and tankers could be used to refuel the lunar Starship in LLO.

Trouble with this is that it doesn't allow the Raptors to be serviced or inspected on Earth, which is an essential part of reuse. It also presents challenges for cargo delivery. You would have to transport your cargo out of the standard Starship and into the lunar Starship in LLO, in zero gravity. It's doable, for sure, but it's not easy.
While there are disadvantages, I suspect the counter argument will be that other advantages will prevail. Cross docking distribution centers make good use of industry standard shipping containers and cargo handling. Same can apply to routine high volume high frequency transport through a gateway or similar.  See discussion elsewhere here on the forum on standardized cargo containers.  Edit:  see https://forum.nasaspaceflight.com/index.php?topic=40454.0
Quote
The other trouble is the very problem with Gateway, because LLO is simply not a good place for staging due to mascons, Earth return timing, and the desire for polar access.
Location, location, location. It may take a while to understand the best place to put the first cross dock distribution center, but that will become clear when the destination is decided.

I like the idea for multiple reasons. A small fleet of space only “last mile” delivery trucks makes sense, and those done need heat shields and 1G landing legs.  Cross dock is a design pattern that is known to work in many shipping situations. And localized repair and maintenance facilities are inevitable anyway. Roadside repair shops the size of a Starship should make an interesting niche market for someone.

I think last mile lunar delivery makes a lot of sense for all the reasons you give, but I don't expect SpaceX to be the company to do it. Design time spent specializing Starship for the Moon is time not spent on improving Starship performance for all scenarios. There's going to be a backlog of iterative improvement opportunities for a good long while.

Last mile seems more of a fit for a company like Intuitive Machines, that' can make that market their main concern. Let SpaceX focus on the big problems only they can solve.

Online whitelancer64

Re: Moon Starship
« Reply #8 on: 09/30/2019 03:06 pm »
it seems to me landing SS on the moon is very wasteful. You are taking 120 tonnes plus fuel down to surface and back up again. Wouldnt cargo transfer in LLO to moon landers be a less wasteful solution. They could standardise container for loading onto the lunar lander, the lunar landers could also be refueled from the SS and delivered to LLO by the SS.

for instance the ARES programme Altair was designed to deliver about 14-15 tonnes of cargo to the moon surface and had a total weight when fueled and loaded of about 45 tonnes. Having said that if SS can refuel as easily as Elon suggests maybe it makes no sense to make another vehicle. After all if Lockheed got its hands on a lunar lander contract we could be looking at 10 years and $15 bill just to develop it, Meanwhile SS will have colonised the inner solar system LOL

It's fuel inefficient - SSTOs always are - but this is kind of an exception because fuel is cheap and Starship's payload capacity is so huge. The benefits far outweigh the drawbacks in this case.
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Offline sevenperforce

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Re: Moon Starship
« Reply #9 on: 09/30/2019 06:49 pm »
If they decide they really do not want to land Starship on the moon, you could still have a cargo Starship fly to LLO and have a 100-tonne-wet lander with a single Vac Raptor in the cargo bay. The lander goes single-stage from Starship to the surface and back, docks, and returns home for inspection and reflight. Landers could be crewed (in which case you'd want to send along a separate Starship for crew transfer) or cargo delivery only.

Offline sevenperforce

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Re: Moon Starship
« Reply #10 on: 09/30/2019 08:51 pm »
Ripped the animation of the lunar landing showing the self-adjusting landing legs:


Offline Lemurion

Re: Moon Starship
« Reply #11 on: 09/30/2019 08:57 pm »
It may be counter-intuitive, but the lack of atmosphere on the Moon may be the one factor that drives a separate, but reusable, landing craft. I don’t think SpaceX is likely to devote that many resources to what is essentially a sideshow, but this is the one situation where I think the people calling for an additional smaller vehicle may have a case.

Offline guckyfan

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Re: Moon Starship
« Reply #12 on: 09/30/2019 09:13 pm »
It may be counter-intuitive, but the lack of atmosphere on the Moon may be the one factor that drives a separate, but reusable, landing craft. I don’t think SpaceX is likely to devote that many resources to what is essentially a sideshow, but this is the one situation where I think the people calling for an additional smaller vehicle may have a case.

The complex multi refueling mission profile introduced by Elon Musk is to enable very high payloads. If the same Starship can deliver 10t and return with only LEO refueling it becomes that "smaller" vehicle.

Offline ncb1397

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Re: Moon Starship
« Reply #13 on: 09/30/2019 09:58 pm »
It may be counter-intuitive, but the lack of atmosphere on the Moon may be the one factor that drives a separate, but reusable, landing craft. I don’t think SpaceX is likely to devote that many resources to what is essentially a sideshow, but this is the one situation where I think the people calling for an additional smaller vehicle may have a case.

The complex multi refueling mission profile introduced by Elon Musk is to enable very high payloads. If the same Starship can deliver 10t and return with only LEO refueling it becomes that "smaller" vehicle.

It really can't. Even 100 t dry mass has negative payload.

Offline friendly3

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Re: Moon Starship
« Reply #14 on: 10/01/2019 12:55 am »
Found this on a french forum, had to share it :


Offline ZachF

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Re: Moon Starship
« Reply #15 on: 10/01/2019 04:06 am »
It seems that eventual tanker variant will have larger 1500+ tonne fuel load in order to refuel in less flights. making this modification will not be hard, you just stretch the tanks internally where payload bay is, and Super heavy will have thrust to spare for the added GTOW.


If tanker variant has 1500+ tonne fuel capacity, tankers could refill a tanker to full and it would have enough fuel to boost to a higher orbit and fully refill a normal Starship there.
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Offline friendly3

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Re: Moon Starship
« Reply #16 on: 10/01/2019 10:14 am »
Another one :


Offline speedevil

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Re: Moon Starship
« Reply #17 on: 10/01/2019 11:02 am »
I am confident we would not see a tank stretch for a lunar mission. What we might see, conceivably, is a version of Starship without wings or a heat shield, with wider landing legs, initially launched unmanned, to act as lunar surface shuttle. It would be substantially lighter and (without doing the math) could probably manage to go from fully-fueled in LEO to a lunar landing and back up to LLO.<snip>
The other trouble is the very problem with Gateway, because LLO is simply not a good place for staging due to mascons, Earth return timing, and the desire for polar access.

LLO orbital stability goes way up if you don't have Apollo era knowledge of the moons gravity field, and have good navigation. Also if you can tolerate a handful of m/s a month.
There are many orbits at various inclinations that are 'stable' with small delta-v.
The LADEE mission operating over the range 20-50km from Nov-2013 to April 2014 used around 150m/s of propellant.

This is probably considerably lower than you'd want for a LLO based station.

This paper gives an example of a quasi-stable orbit, initially 200km circular 28 degree inclined, stable over 2 years with no delta-v.

And others of polar orbits, at 40km altitude and 100m/s/year.

There is no reason to have retanking happen in a time-constrained environment.

Of SS and the moon.
With retanking in LEO, it can land 200 tons on the moon and not return.
(6km/s, 125 tons dry, ISP=380, 1600 full)

Without additional tanks, with no cargo, it can land on the moon with 160 tons remnant propellant.
It can then take off and return to earth with 20 tons margin. (2.5km/s).
So, operations on the moon, retanking only in LEO are quite limited if you want to return, and you get of the order of 10 tons payload to and from the moon.

Put another way -
1 ton per launch. (10t/10 launches)

If we fill a tanker in LEO, move it to ~GTO (2300m/s eliptical orbit), we end up with half the propellant we started with. Fill a depot there (lightly insulated tanker), and you end up with propellant at this higher orbit costing twice what it does on earth, but allowing considerably more expanded missions.

Now in order to get 6km/s from LEO (lunar surface) you need 3.7km/s from the depot.
This gives you 520 tons landed on the moon - 400 tons of propellant/cargo.

If you want to return, you now have 240 tons of spare propellant/cargo - you can use this to either land >250 tons, and then return empty, or to (for example)  land 50 tons and return 100 tons.

5 tons/launch (100 tons for 22 flights. (and a prepositioned tanker)).

You can further greatly optimise this by adding another tanker in low lunar orbit that you offload propellant to on arriving and pick it up on departure.

A filled  in GTO SS (which costs you 17 launches) gets you 800 tons of propellant into LLO.
Or in other words, you need around 25 launches (average) to get a full SS worth of propellant in LLO.

As a more general solution - what is the approximate amount this scheme can land on the moon - if we use frequent depots and always fly between half empty and full?

This can be simply worked out by using the rocket equation for 6km/s, and neglecting the ship mass, as it is effectively just a slightly reduced ISP.
(1500->750 tons @380ISP = 2580m/s.
1500->750+(125) @380ISP = 2007
Effective ISP = 380*(2007/2580 = 295s) (This only works for the LEO->GTO orbit strictly, you need an extra few percent for returning GTO-LLO tankers to get to earths atmosphere)
This all winds up as - once you average it out around 200 tons payload on the moon (or being returned from the moon) per filled vehicle in LEO. (around 120 tons there, 120 tons back).

In short - some operational complexity - three tankers - in addition to your SS, rather than the minimal one, lets you go from under one ton per tanker launch to around twenty tons cargo from/to the lunar surface reusably.

20 tons/launch.

LEO->GTO->LLO->Lunar surface is nice, because each step only burns half your initial mass - this means your final mass ratio ends up at 7:1 or so, so the mass of the tanker can almost be neglected.

It is not the only possible selection of orbits - there is some argument for putting L1 or even NHRO in there.
But, if you're doing this, you do not care one tiny bit about masscons - as any fuel rich system can trivially manage ~100m/s/year or so.

The above does assume some things - but I think they are reasonable to assume.
For example, that depots are insulatable simply and their loss is minimal. I think it is reasonable to assume this for several reasons.
For GTO, for example once you have deployed a very small sunshield around the base of the vehicle (~12m in diameter) from one of the underseat storage compartments, and pointed the vehicle base at the sun, and oriented the shiny side towards earth, the heat gain during the ~30 minute pass close to the earth is managable, given  the heat loss during the ~6 hours of the rest of the orbit.
I like the concept of putting the solar panels on the other side of this small sunshield - though there are of course many other options.
« Last Edit: 10/01/2019 11:12 am by speedevil »

Online Yggdrasill

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Re: Moon Starship
« Reply #18 on: 10/01/2019 11:27 am »
I think a lightly modified variant of Starship could make sense for the moon.

- Get rid of the aerodynamic surfaces.
- Get rid of the ceramic tiles.
- Get rid of the current Raptor layout and replace with 2x vacuum Raptor with gimble.

Use this for travel between lunar surface and LLO, and transfer fuel, crew and cargo there.

(And if you want to go a bit beyond the "light" modifications - you could shrink the size of the tanks, add windows on the underside for moon habitation, redesign the interstage/landing gear area for moon landing only. Maybe using aluminium.)
« Last Edit: 10/01/2019 11:42 am by Yggdrasill »

Offline KelvinZero

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Re: Moon Starship
« Reply #19 on: 10/01/2019 12:53 pm »
- Get rid of the aerodynamic surfaces.
- Get rid of the ceramic tiles.
- Get rid of the current Raptor layout and replace with 2x vacuum Raptor with gimble.

Use this for travel between lunar surface and LLO, and transfer fuel, crew and cargo there.
That is similar to sevenperforce's idea near the top of the thread. This seems very natural to me.
* pretty simple requirements and also Elon has mentioned some expendable versions for deep space robotic missions that are probably not that different from this.
* Surely this makes sense in the further future if we develop enough infrastructure, eg the ability to service and replace engines without returning to earth. Unlike earth, there will not be any wear of the thermal protection. The hull should last for ages.
* It could possibly solve some problems for initial unmanned missions landing on unprepared surfaces, eg to deploy the initial landing pads for later manned missions.

 

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