Author Topic: ITS for the Moon  (Read 48132 times)

Offline RocketmanUS

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Re: ITS for the Moon
« Reply #60 on: 10/05/2017 07:38 pm »
@ ciscosdad
Not having crew spending unneeded time in the Van Allen belts is why I was looking at Steven's concept for this new BFS.

@envy887
Thanks, what I needed was the number of payload mass using Steven's concept. So what you got was 23 t payload.

Any ides on how much unused propellant mass there would be? That is the unused in the engines and that used to pressurize the tanks.

Steven's OP had two concepts, you'll have to clarify which you meant:
1) Refuel in LEO, direct lunar landing and return to Earth surface (this had negative payload), and
2) Refuel in LEO, land on lunar surface, ascend to LLO rendezvous for return fuel, then direct return and landing on Earth (105 t payload landed).

I slightly modified these concepts to:
3) Refuel in LEO, direct landing and return to LEO with aerobraking, refuel in LEO before landing on Earth surface (10 t payload for full round trip), and
4) Refuel in LEO, boost to EEO, top off before TLI, descent to LLO and lunar landing, drop off 150 t payload, return to LLO empty, pick up fuel for TEI, aerobrake into LEO, pick up fuel for Earth landing.

My mission profiles trade some operational complexity for a lot more payload; I get 43% more payload to the lunar surface despite 38% less IMLEO, by having 10 rendezvous instead of 7. One additional rendezvous is in LEO, and the other 2 in low elliptical Earth orbit, apogee ~3500 km.
Option #2 please for the 2017 version of BFR/BFS.

Using Steven's delta-v figures and the #2 mission profile, I get 57 tonnes for the 2017 BFR vs. 105 tonnes for the 2016 architecture.
Thanks.

Did you off load the return propellant before Lunar descent into another BFS that just came up from moon for return trip back to Earth? The number you have ( 57 t ) would be for the first BFR landing I believe , all the other BFR's would have a lower payload mass. Keep in mind that at around 20 t payload that payload also returns back to Earth ( this assumes crew missions ).

Offline envy887

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Re: ITS for the Moon
« Reply #61 on: 10/05/2017 09:16 pm »
Did you off load the return propellant before Lunar descent into another BFS that just came up from moon for return trip back to Earth? The number you have ( 57 t ) would be for the first BFR landing I believe , all the other BFR's would have a lower payload mass. Keep in mind that at around 20 t payload that payload also returns back to Earth ( this assumes crew missions ).

Yes. 57 tonnes is for continuous operation, the first one would be slightly higher.

I'll run through again with a round trip payload, but I expect 20 tonnes will be about right.

BTW, for cargo missions I expect SpaceX will want to stage in EEO and aerobrake back to LEO as it more than doubles payload. The orbit will have sufficient inclination and a low enough apogee to avoid most of the inner Van Allen Belt. It might even be acceptable for crew.
« Last Edit: 10/05/2017 09:19 pm by envy887 »

Offline Steven Pietrobon

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Re: ITS for the Moon
« Reply #62 on: 10/08/2017 01:37 am »
OK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline RocketmanUS

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Re: ITS for the Moon
« Reply #63 on: 10/09/2017 05:09 am »
OK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.
Thanks.
That is with the cargo left on the moon.
What I was doing was bringing the cargo back. I did this to see how much return payload mass could be available for a crewed mission. That is the crew mass , their suits, ect.

Edit:
Ran the numbers for payload round trip from LEO ( refueled ) to Lunar surface and back to Earth. This is with estimated unusable propellant ( 8,000 kg ), Still would need an expert  answer for better estimate. Finding was 12 t payload round trip picking up return propellant in LLO from incoming BFS before return trip to Earth.

Edit:
Typo fixed , LEO to LLO
« Last Edit: 10/12/2017 07:53 pm by RocketmanUS »

Offline envy887

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Re: ITS for the Moon
« Reply #64 on: 10/12/2017 05:30 pm »
OK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.
Thanks.
That is with the cargo left on the moon.
What I was doing was bringing the cargo back. I did this to see how much return payload mass could be available for a crewed mission. That is the crew mass , their suits, ect.

Edit:
Ran the numbers for payload round trip from LEO ( refueled ) to Lunar surface and back to Earth. This is with estimated unusable propellant ( 8,000 kg ), Still would need an expert  answer for better estimate. Finding was 12 t payload round trip picking up return propellant in LEO from incoming BFS before return trip to Earth.

Picking up return propellant in LLO or LEO? It should be possible to do both, which combined with a tanker top-off in low EEO gives a round-trip payload of over 50 tonnes.

Offline RocketmanUS

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Re: ITS for the Moon
« Reply #65 on: 10/12/2017 07:58 pm »
OK, ran my software for the new BFR. First flight payload mass is 90.5 t, with subsequent flights having a payload of 47.6 t. Transfer propellant in LLO is 62.0 t. Would need seven refuelling flights (or eight flights altogether) for each mission! For the first flight we have propellant mass of 7x150 + 150-90.5 = 1109.5 t, just over the 1100 t capability of BFS. Software attached.
Thanks.
That is with the cargo left on the moon.
What I was doing was bringing the cargo back. I did this to see how much return payload mass could be available for a crewed mission. That is the crew mass , their suits, ect.

Edit:
Ran the numbers for payload round trip from LEO ( refueled ) to Lunar surface and back to Earth. This is with estimated unusable propellant ( 8,000 kg ), Still would need an expert  answer for better estimate. Finding was 12 t payload round trip picking up return propellant in LEO from incoming BFS before return trip to Earth.

Picking up return propellant in LLO or LEO? It should be possible to do both, which combined with a tanker top-off in low EEO gives a round-trip payload of over 50 tonnes.
Typo fixed. Thanks for pointing out. That is LLO.

After TEI how much propellant is needed to brake into EEO?

Offline envy887

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Re: ITS for the Moon
« Reply #66 on: 10/12/2017 09:17 pm »
...
After TEI how much propellant is needed to brake into EEO?

If you are braking into orbit it makes more sense to go to LEO, not EEO.

But it doesn't really matter for this calculation. An aerobrake orbit will dip into the atmosphere with a perigee of around 60-80 km. Pulling the perigee up to ~300 km so you don't reenter on the next orbit takes about 55-65 m/s at apogee.

Compare this to landing which takes 500 to 800 m/s, and this fuel has to go at least to LLO and back, and you can see why it helps the payload a lot.
« Last Edit: 10/12/2017 09:18 pm by envy887 »

Offline RocketmanUS

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Re: ITS for the Moon
« Reply #67 on: 10/13/2017 04:51 am »
...
After TEI how much propellant is needed to brake into EEO?

If you are braking into orbit it makes more sense to go to LEO, not EEO.

But it doesn't really matter for this calculation. An aerobrake orbit will dip into the atmosphere with a perigee of around 60-80 km. Pulling the perigee up to ~300 km so you don't reenter on the next orbit takes about 55-65 m/s at apogee.

Compare this to landing which takes 500 to 800 m/s, and this fuel has to go at least to LLO and back, and you can see why it helps the payload a lot.
I ran some quick numbers and see what you mean. If I have time I'll run the numbers through to see how close I get to your payload mass round trip. For landing back on Earth will need deorbit burn propellant alwell. But that is brought up from Earth with the landing propellant and would not effect the round trip payload mass if done by LEO tanker.

Using both LLO and then LEO for adding propellant would be better than using elliptical orbits for Lunar departure.

Offline corneliussulla

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Re: ITS for the Moon
« Reply #68 on: 10/18/2017 06:56 am »
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.

Online guckyfan

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Re: ITS for the Moon
« Reply #69 on: 10/18/2017 09:41 am »
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.

ISRU for LOX only could make a lot of sense. After all LOX is ~80% of propellant mass. There is a concept worked on to produce LOX from SiO2 which is available everywhere on the moon. But worth it probably only when regular large payloads to the moon are needed.

Offline envy887

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Re: ITS for the Moon
« Reply #70 on: 10/18/2017 05:27 pm »
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.

ISRU for LOX only could make a lot of sense. After all LOX is ~80% of propellant mass. There is a concept worked on to produce LOX from SiO2 which is available everywhere on the moon. But worth it probably only when regular large payloads to the moon are needed.

Lunar ISRU trades against 3 or 4 tanker flights to LEO, to land a 150 tonne payload on the Moon and return empty, or landing 50 tonnes and returning 50 tonnes. Tanker flights have to be pretty expensive to make ISRU worthwhile (this is not the case form Mars since Mars is so much more difficult to return from).

I haven't worked the numbers for landing 150 tonnes and returning 50 tonnes, but that's the limit of the BFR/BFS architecture unless you go to LEO payload transfer - and even then it's likely volume limited for most payloads. I don't think lunar ISRU fits well with BFS/BFR. But it does make sense to have it for at least an emergency backup O2 and H2O source if you have a lunar base.

Offline A_M_Swallow

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Re: ITS for the Moon
« Reply #71 on: 10/18/2017 11:24 pm »
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.

ISRU for LOX only could make a lot of sense. After all LOX is ~80% of propellant mass. There is a concept worked on to produce LOX from SiO2 which is available everywhere on the moon. But worth it probably only when regular large payloads to the moon are needed.

Lunar ISRU trades against 3 or 4 tanker flights to LEO, to land a 150 tonne payload on the Moon and return empty, or landing 50 tonnes and returning 50 tonnes. Tanker flights have to be pretty expensive to make ISRU worthwhile (this is not the case form Mars since Mars is so much more difficult to return from).

I haven't worked the numbers for landing 150 tonnes and returning 50 tonnes, but that's the limit of the BFR/BFS architecture unless you go to LEO payload transfer - and even then it's likely volume limited for most payloads. I don't think lunar ISRU fits well with BFS/BFR. But it does make sense to have it for at least an emergency backup O2 and H2O source if you have a lunar base.

Have you taken into account ISRU machinery lasting about 10-15 years? This means it can make more fuel than it weighs.

Offline Robotbeat

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Re: ITS for the Moon
« Reply #72 on: 10/19/2017 02:55 am »
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.
No, it'd make it far more complex. If you need a lot of payload on or off the Moon, it might still make sense cost-wise, but it's FAR simpler without lunar ISRU.
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Online guckyfan

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Re: ITS for the Moon
« Reply #73 on: 10/19/2017 03:27 pm »
ISRU for propellant on the moon would make the whole BFS to the moon proposal much simpler. However it doesnt appear to be as straight forward as on Mars from what I read.
No, it'd make it far more complex. If you need a lot of payload on or off the Moon, it might still make sense cost-wise, but it's FAR simpler without lunar ISRU.

I agree it makes it more complex. But should be worth it for a major base that needs multiple thousands of tons payload to the moon.

May I point out that this discussion is in stark contrast to arguments, we need to produce propellant on the moon to facilitate Mars flights? I never thought lunar propellant makes a lot of sense for Mars but there is plenty of argument for it.

Offline oldAtlas_Eguy

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Re: ITS for the Moon
« Reply #74 on: 10/19/2017 04:32 pm »
I was trying to find if it was possible to have frozen CO2 traped with the water at the Lunar pols. The temperatures are -237 degrees C. This looks to be cold enough for frozen CO2 but the value for temp of frozen CO2 in vacuum is seemingly not available. Also could the CO2 bond (not a chemical bond but there is also a possibility of C and O molecules performing bonds) with other items in the regolith allowing it to freeze at higher temps.

http://www.chemicalogic.com/Documents/co2_phase_diagram.pdf

I just looked it up but LCROSS detected carbon monoxide in the plume. So it could be possible to make some Metholox with the volatiles in the Lunar pol regolith.
« Last Edit: 10/19/2017 04:48 pm by oldAtlas_Eguy »

Offline KelvinZero

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Re: ITS for the Moon
« Reply #75 on: 10/19/2017 10:06 pm »
Some dispute about whether the CO results are trustworthy, apparently. We just have to go and look. It is definitely possible though. It is frustrating that such huge HSF architectures are being finalised without this basic information verified. This is not a SpaceX criticism.

Jon Goff mentions some Paul Spudis doubt here:
https://forum.nasaspaceflight.com/index.php?topic=39559.msg1612453#msg1612453
« Last Edit: 10/19/2017 10:08 pm by KelvinZero »

Offline oldAtlas_Eguy

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Re: ITS for the Moon
« Reply #76 on: 10/20/2017 04:43 pm »
Some dispute about whether the CO results are trustworthy, apparently. We just have to go and look. It is definitely possible though. It is frustrating that such huge HSF architectures are being finalised without this basic information verified. This is not a SpaceX criticism.

Jon Goff mentions some Paul Spudis doubt here:
https://forum.nasaspaceflight.com/index.php?topic=39559.msg1612453#msg1612453
But primarily any significant source of carbon found would enable the creation of methane when combined with water and other O2 from oxides. Unfortunately most of the surface, dark craters, and lava tubes have never been explored or tested for specific makeup of the contents. So we know our understanding from Apollo was not the whole picture of the Lunar resources. But we do not know what the resources extent or makeup is at this point, only educated guesses at what it could be.

Because BFR will not depend at least initially on any Lunar resources this will enable the ability to explore and develop resources which could then lower the costs of the transport to and from the Lunar surface. a bootstraping event which because of the massive transportation flow to the Moon there would be great incentive for others to develop capabilities on the Moon that would allow by selling products (propellant in some form) to the transporters that enables them to lower prices and increase volume which increases total revenue which increase profits. This is the essence of the bootstrap but in this case for a commercial services industry based on the development of Lunar resources. Growth of bases and capabilities would grow at an exponential rate which at first  would hardly be noticeable but at 10 20 years after BFR first landing on the Moon would be showing significant Lunar industry growth increases which itself would be doing at an increasing rate.

Offline speedevil

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Re: ITS for the Moon
« Reply #77 on: 11/19/2017 05:03 pm »
But primarily any significant source of carbon found would enable the creation of methane when combined with water and other O2 from oxides.
I now wonder at what velocity you can hard-land coal on the moon, and have it remain in the general area at moderate concentration.
(I would be astonished if this was actually worthwhile)

Offline Bynaus

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Re: ITS for the Moon
« Reply #78 on: 11/19/2017 07:07 pm »
There's plenty of carbon in comets (e.g., measured in comas), up to 4% carbon in chondritic meteorites, and there are even some "ultracarbonaceous" interplanetary dust particles which are 80% C. Strong heating upon impact will primarily make CO and CO2 (depending on availability), which are then both easily trapped at the polar cold traps. There is every reason to expect large deposits of carbon in the polar craters. The LCROSS results fit in well with this expectation. Still, it needs to be confirmed on-site.
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Offline lamontagne

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Re: ITS for the Moon
« Reply #79 on: 11/19/2017 09:09 pm »
How about this paper

https://www.hou.usra.edu/meetings/lpsc2016/pdf/1415.pdf

Proposing, I think, large amounts of meteorite impact carbon?  Doesn't quite seem convincing but it's an interesting possibility.

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