Replacing SLS/Orion using Starship HLS and Crew Dragon (AI data allowed)

[Roy_H]

Anyway:
3,000*200km means passing through the inner belt peak twice each orbit. For long RPOD operations it looks like it might be better to go to something like 7,000*4,000km orbit. The extra delta-v cost of doing this might not be worth it if RPOD operations don't take long and you have sufficient shielding.

No, I believe we have arrived at the sweet spot. The higher orbit just means more fuel tankers and I just don't think the radiation issue is that important.

This mission profile uses almost the same equipment that SpaceX is building for Artemis as they are planning on adding a tanker to refuel at Gateway. The only changes I have added are the lifeboat part of the tanker and the 50 tons of PE radiation shielding on the HLS and 10 tons of PE shielding on the Lifeboat Tanker. In my searches about NASA for MLI, I think I read that this was planned for HLS, so I assumed it is planned for the tanker as well. In any case the addition of 50 tons of PE may seem extravagant as the existing plan is to build a radiation shelter where the astronauts can huddle during the worst parts of the mission. But I figured that if it could be accommodated in the mass budget, what the hell, why not give the astronauts the freedom to go about their work at all times and live in an environment where their total exposure will be less. This makes the several orbits in the HEEO through the Van Allan Belt of minimal concern.

Another thing that I only realized lately is that I have assumed that the astronauts and payload to moon's surface would all be in one ship. Now I understand that the Artemis plan is for HLS to carry astronauts and a separate cargo version of HLS to deliver 1 ton payload. Splitting up these functions would allow a somewhat lower HEEO orbit, but not enough to make any difference in terms of radiation exposure. So the mission as I have described would be much cheaper than sending two different ships to the moon.

So how realistic is a goal of say only 1 orbit, about 2.5 hours, in HEEO to re-fuel? The Starship Tanker could be timed to arrive at the HEEO orbit at the same time, or even before the HLS does. The Lifeboat Tanker could stay for a 2nd orbit. It would just arrive at LLO a few hours later.

I want to thank all those who have contributed to this interesting thread, even those from the original thread where I got some ideas from. I believe we have arrived at a very desirable and doable plan for supporting a moon base. What are the chances of SpaceX actually reading this thread and giving it serious consideration?

[Roy_H]

I think all this could be done under the existing Artemis contract.
The initial HLS could be scrapped as intended in the demo mission.
The second one used to fulfill Artemis III contract, as it does not require the 100t payload and the detour to NRHO would consume less fuel than saved by no payload.
This would allow the HLS and LT to return to LEO as planned and the HLS could be re-supplied, refurbished if necessary in LEO and sent back to NHRO for Artemis IV.

My whole point is that the modifications and additional costs such as adding the lifeboat part to the tanker could be done within the existing Artemis contract budget by eliminating the building of a 3rd HLS and fulfill all the Artemis contract goals.

[crandles57]

New updated mission profile diagram attached.

I think you want to launch HEEO depot, 4 tankers, refuel HEEO depot, send HEEO depot and lifeboat depot to the 3000*200 orbit and refuel the lifeboat tanker (and maybe send lifeboat depot onwards to get it out of the way) before launching astronauts in dragon. This is to save time in VAB for astronauts by the fuel depot being there ready and waiting to refuel them as fast as possible.

It would be cheaper and easier to apply MLI and solar panels to body of lunar ships if this can survive launch.

~150 km circular orbit might be better for tanker to depot fuelling than 200km.

It is just confusing not using the depot terminology that others are using.

[Roy_H]

Not much change here. Just thought I would consolidate some things spread out over several posts and correct an error in calculation. Yes, I depend too much on Grok, just have to make sure my questions are worded properly. Turns out the Lifeboat Depot can be a little smaller, and I included the option of a larger Lifeboat Depot (LD) to reduce time astronauts spend in Van Allan Belt.

Mission Objectives:

1, Most fuel efficient - no detour to NHRO, minimum fuel for Lunar landing and accent.

2. Deliver 100 tons payload to Lunar surface.

3. Provide radiation protection for astronauts to NASA recommendation.

4. Make all hardware re-useable, hardware is expensive, fuel is cheap.

5. Provide lifeboat alternative if prop transfer at LLO fails. HLS and Depot tanker can dock nose-to-nose. Failing that EVA transfer could be possible.

Depot tanker has Orion sized crew quarters in nose as lifeboat for emergency. HLS and lifeboats have PE radiation shielding (for entire living area, not just shelter) to minimum NASA guideline. I don't know enough about space craft construction, but I assume crew quarters have double hull. I envision this to be 14 cm apart and filled with Poly Ethelene This would also provide extra protection to small debris that might punch through the outer hull. I have allotted 50 tons PE on HLS and 10 tons on Lifeboat Depot, LD.

HLS and LD each have 3 gimbaled vac Raptors, no sea level Raptors. I do not know the dry mass, so these calculations are based on a dry mass for HLS of 120 tons + 50 tons PE for a total of 170 tons. The LD is 95 tons + 10 tons for crew quarters and 10 tones for PE. I believe these estimates to be very conservative.

Edit: Another assumption. Fuel is kept at 95°K to 100°K, CH4 at 1 Bar, O2 at 6 Bar. Both liquid under this condition.

Initial HLS launch includes 100 ton payload. Subsequent missions would have HLS payload delivered by Starship in 200km circular orbit.

Two variations on LD, the minimal one would have 1,240 ton capacity for fuel and require a fuel too-op for HLS and LD on return to HEEO. A larger 1,535 ton version would allow returning ships to avoid HEEO and go directly to a 500km circular orbit.

Mission Profile:

1. launch HLS, Lifeboat Depot, and cargo Starship to 200km LEO.

2. Robotics are used to remove supplies from Starship and assemble solar panels, radiator, and MLI shielding on HLS and Lifeboat Depot.

3. LD and HLS are fully fueled by 20 Starship Tankers. Assuming 150t fuel delivered per flight. 16 flights for filling at 200km LEO and an ST with 3 more ST flights adding fuel to it would fly to HEEO to top off HLS and LD. The larger Depot option would require 2 more flights for LEO fills and 1 more for HEEO fill.

4. Top up ST flies to 3,000km x 200km HEEO and waits for LD and HLS.

5. Dragon delivers astronauts to HLS. Dragon performs EDL to Earth.

6. LD flies to HEEO and spends two obits there being topped up by the waiting ST. They would mate at Apogee spend the portion through Perigee loading the fuel, and undock at Apogee.

7. LD performs TLI to LLO at 100km altitude. Polar orbit.

8. HLS flies to HEEO and performs same fuel top up orbit. The value in this sequence is to minimize time astronauts spend in Van Allan Belt, and be assured that LD is successfully on the way.

9. HLS performs TLI to LLO at 100km altitude. Polar orbit.

10. LD adds 62 tons fuel to HLS in LLO.

11. HLS performs Moon landing remains for about 2 weeks and unloads 100t cargo.

12. HLS returns to LLO and receives 205 tons fuel to HEEO or 363 tons fuel for return to 500km LEO.
 
13. LD and HLS return to HEEO.

14. One more Starship Tanker meets HLS and LD adding fuel to enable them to go to 500km circular orbit and later to 200km circular.

15. HLS and LD descend to 500km circular orbit.

16. Astronauts transfer to Dragon for EDL to Earth.

17. Lifeboat Depot and HLS remain in orbit for future missions. When required they will return to 200km altitude for fuel and cargo for next mission.

[crandles57]

Found this re SpaceX's suggestion for Final Tanking Orbit 'FTO'.

https://danielmarin.naukas.com/files/2024/12/Technical-Annex.pdf

Medium-Earth Orbit/High-Earth Orbit/Final Tanking Orbit. 
Missions beyond LEO will also require space station operations in medium-Earth orbit (“MEO”) to high-Earth orbit (“HEO”).  For example, crewed lunar missions will include a secondary propellant transfer in MEO/HEO, the Final Tanking Orbit (“FTO”).  Operations in MEO/HEO will occur in an elliptical orbit of 281 km x 34,534 km and an altitude tolerance of +116,000/-24,000 km apogee and +/- 100 km perigee, with inclination between 28 and 33 degrees (+/- 2 degrees). 

So it seems SpaceX isn't considering less than 181*10000 km as the FTO.

[Roy_H]

So it seems SpaceX isn't considering less than 181*10000 km as the FTO.

No, I wouldn't take that as a limit. It is good to see that they are considering taking the HLS back to Earth orbit for re-use instead of leaving it in NHRO and re-suppling there. If they go through the same optimizing process I did, they will come to the same conclusion.

Namely don't take any more fuel to Moon's surface then you have to. Have a depot in LLO to re-fuel for home trip.
It's just foolish to take the fuel required to return to any orbit around Earth, in this case their MEO to the moon surface and back to LLO.

Once you have made that decision, going to the 200km x 3,000km orbit I recommend results in the accompanying Depot to be about the same size as HLS. If you choose a higher orbit such as they have the accompanying tanker gets smaller, until at their 34,534km orbit, it is not needed at all. But it becomes much more difficult and costly to re-supply and re-fuel in that high orbit. You want to do as much of that in 200km circular as possible. Choosing a lower HEEO such as 200km x 2,000km results in a larger accompanying Depot, with no advantage until you choose an orbit below the Van Allan Belt at which point as my earlier attempts show, require either a monster Depot or two Depots. What I have arrived at is the sweet spot. I think they will too.

[crandles57]

So it seems SpaceX isn't considering less than 181*10000 km as the FTO.

No, I wouldn't take that as a limit. It is good to see that they are considering taking the HLS back to Earth orbit for re-use instead of leaving it in NHRO and re-suppling there. If they go through the same optimizing process I did, they will come to the same conclusion.

Namely don't take any more fuel to Moon's surface then you have to. Have a depot in LLO to re-fuel for home trip.
It's just foolish to take the fuel required to return to any orbit around Earth, in this case their MEO to the moon surface and back to LLO.

Once you have made that decision, going to the 200km x 3,000km orbit I recommend results in the accompanying Depot to be about the same size as HLS. If you choose a higher orbit such as they have the accompanying tanker gets smaller, until at their 34,534km orbit, it is not needed at all. But it becomes much more difficult and costly to re-supply and re-fuel in that high orbit. You want to do as much of that in 200km circular as possible. Choosing a lower HEEO such as 200km x 2,000km results in a larger accompanying Depot, with no advantage until you choose an orbit below the Van Allan Belt at which point as my earlier attempts show, require either a monster Depot or two Depots. What I have arrived at is the sweet spot. I think they will too.

Isn't the problem with LLO that you get lots of reflected radiation off the moon and a small sunshade is unlikely to cope unless it completely surrounds vehicle so boil off is a big problem? Hence suggested use of NRHO to get the prop store further from the moon?

200*3000 km means you pass slowly through the inner VAB peak at about 2000km. Using 200*10000 means you pass more quickly through those high risk altitudes. The orbit also takes longer which gives you more time to complete RPOD for astronaut transfer allowing fewer orbits and hence passes through inner belt peak before TLI.

[Robotbeat]

Note SpaceX will doubtless want margin for initial crewed missions and to avoid an additional tanking event before bringing crew home.
I agree in the long term it makes sense as an optimization. But in the near term, tanker launches are relatively cheap.

[Roy_H]

Isn't the problem with LLO that you get lots of reflected radiation off the moon and a small sunshade is unlikely to cope unless it completely surrounds vehicle so boil off is a big problem? Hence suggested use of NRHO to get the prop store further from the moon?

200*3000 km means you pass slowly through the inner VAB peak at about 2000km. Using 200*10000 means you pass more quickly through those high risk altitudes. The orbit also takes longer which gives you more time to complete RPOD for astronaut transfer allowing fewer orbits and hence passes through inner belt peak before TLI.

The sun shade does completely surround the cylindrical part of the rocket in both cases. There is the addition of the solar cells and active cooling. Assuming that the landing spot chosen, the solar cells will not be in shadow and the expectation is zero boil off for both HLS and LD. Since boil off is not a problem the slight savings going to NHRO is irrelevant.

I agree on the statement about the higher HEEO where the HLS passes quickly through Van Allan Belt. However, the 3,000km orbit only goes into the lower belt whereas the higher orbit goes through both belts. Astronauts have to go through the VABs to get to the moon and back so we are arguing about increased amount. How many orbits will the HLS spend in the higher 34,500km elliptical orbit? In my plan, I think it can be down to 4, 2 going and 2 returning.

However, I grant that it is a fair argument. In my plan I have added a significant amount of radiation shielding, and we don't know how much SpaceX is planning on. If the shielding is minimal, then I agree the higher orbit will be better for the astronauts at the expense of more difficult fuel transfer to that higher orbit. Unfortunately they don't go into details, but I would expect that fueling could be done in a single orbit and then the HLS could go to an LEO circular such as my 500km choice. This would result in much lower time in the Van Allan Belts.

I am very pleased that SpaceX is considering an option to bring the HLS back to LEO for re-use no matter how it is done.

[Roy_H]

Note SpaceX will doubtless want margin for initial crewed missions and to avoid an additional tanking event before bringing crew home.
I agree in the long term it makes sense as an optimization. But in the near term, tanker launches are relatively cheap.

I am not sure I understand your argument. Any mission that includes bringing the HLS back to Earth orbit will require re-fueling. How is this "margin" to be accomplished? The standard fuel margin is 5% and that has been accounted for in my proposal.

[Roy_H]

I did another quick estimate of fuel requirements for another variation and will qualify this as a rough estimate as I did not give Grok all the finer details. However. in this one I specified that HLS would be fully fueled in a 800km circular orbit (below Van Alan Belt), and LD fully fueled in 4000km x 200km orbit (no astronauts so no radiation problem). As before HLS has two fuel transfers in LLO, before and after moon landing. This time the HLS returns directly to 500km circular orbit and LD returns to 4000km x 200km for additional fuel to return to 500km circular. This requires the LD to be about 1350 ton capacity. I did not ask for how many ST flights required.

This plan retained my requirement of 50 tons PE shielding and 100 ton payload to Moon surface. It has the benefit that HLS does not have to spend any extra orbits in Van Allan Belt. Astronauts would board the HLS at 200km orbit as before from Dragon. I think it is best to plan on Dragon performing EDL and being re-launched to pick up crew on return. That way the Dragon can be launched to match whatever orbit timing and inclination the HLS returns to at 500km.

[crandles57]

The orbital period for a satellite in a 200 x 10000 km altitude Earth orbit is approximately 3.4 hours.
The orbital period for a satellite in a 200 x 3000 km altitude Earth orbit is approximately 1.84 hours.

Are those periods correct?

I am not sure 3.4 hours is enough for elliptical orbit insertion burn, POD for docking, hatch opening, astronaut transfer, hatch closing, detach dragon, and TLI burn at perigee. However, 1.84 hour period seems likely to involve a few orbits?

>"How is this "margin" to be accomplished?"
If you fully refuel in 200*10000 then you need less from there to moon than if you are in 200*3000 km orbit. Yes it does take more tanker launches to get fully fuelled in 200*10000 orbit than in 200*3000 km orbit. Maybe this is a price worth paying early on for extra fuel safety margin and reduced radiation dose for astronauts during transfer time (or in refuelling time if the astronauts are transferred at lower altitude) is also a factor in favour? Probably also reduces refuelling time and launches for way back down if not eliminating it?

>"However, the 3,000km orbit only goes into the lower belt whereas the higher orbit goes through both belts"
200*10000 doesn't go though the higher belt but I accept that 200*~30k km does go through both.

[Roy_H]

I am not sure 3.4 hours is enough for elliptical orbit insertion burn, POD for docking, hatch opening, astronaut transfer, hatch closing, detach dragon, and TLI burn at perigee. However, 1.84 hour period seems likely to involve a few orbits?

>"How is this "margin" to be accomplished?"
If you fully refuel in 200*10000 then you need less from there to moon than if you are in 200*3000 km orbit.

Your link makes no mention of a 200*10000 km orbit, only 281km * 34,534km. Also it only mentions refueling, no mention of astronauts transferring from Dragon. That orbit is 10 hours and 8 minutes. Lots of time to refuel, so I would expect one orbit going up and one coming back. HLS has lots of lift capacity to include extra shielding. You do not want to send Dragon through the Van Alan Belt if it can be avoided. Also the inner belt is far more dangerous than the outer belt.

I agree that there are many trade-off scenarios and the one suggested in your link makes me believe that orbit is only for refueling, not astronaut transfer, and probably does not require refueling in LLO. Too many unknowns.

[crandles57]

Your link makes no mention of a 200*10000 km orbit, only 281km * 34,534km. Also it only mentions refueling, no mention of astronauts transferring from Dragon. That orbit is 10 hours and 8 minutes. Lots of time to refuel, so I would expect one orbit going up and one coming back. HLS has lots of lift capacity to include extra shielding. You do not want to send Dragon through the Van Alan Belt if it can be avoided. Also the inner belt is far more dangerous than the outer belt.

I agree that there are many trade-off scenarios and the one suggested in your link makes me believe that orbit is only for refueling, not astronaut transfer, and probably does not require refueling in LLO. Too many unknowns.

Found the document shown at
https://danielmarin.naukas.com/files/2024/12/Technical-Annex.pdf

Medium-Earth Orbit/High-Earth Orbit/Final Tanking Orbit. 
Missions beyond LEO will also require space station operations in medium-Earth orbit (“MEO”) to high-Earth orbit (“HEO”).  For example, crewed lunar missions will include a secondary propellant transfer in MEO/HEO, the Final Tanking Orbit (“FTO”).  Operations in MEO/HEO will occur in an elliptical orbit of 281 km x 34,534 km and an altitude tolerance of +116,000/-24,000 km apogee and +/- 100 km perigee, with inclination between 28 and 33 degrees (+/- 2 degrees). 

34534-24000=10534 but I rounded this down to 10000km apogee. So it sort of does mention it, admittedly only as an extreme of the range.

I think you are trying to do more mass than they are. This possibly makes your lower elliptical refuelling orbit seem strange but perhaps it is explained because they are building in more fuel safety margin and less mass for first few attempts to avoid refuelling in LLO and on return journey?

[Roy_H]

34534-24000=10534 but I rounded this down to 10000km apogee. So it sort of does mention it, admittedly only as an extreme of the range.

I think you are trying to do more mass than they are. This possibly makes your lower elliptical refuelling orbit seem strange but perhaps it is explained because they are building in more fuel safety margin and less mass for first few attempts to avoid refueling in LLO and on return journey?

Absolutely true. I have taken the highest possible mass (worst case condition) quite deliberately as anything less will require less fuel, and I expect they are not. But all I think this shows is that they are considering refueling in some high orbit (huge range possible) and we cannot make many conclusions on what mass, or how much fuel.

I suspect that my latest variation will require more fuel, but I should probably go to the effort to find out. I do find it interesting that SpaceX does consider at least one extra pass through the Van Allan Belts acceptable as a price to bring HLS back to LEO. Although initial mission will be crewless, follow on will be crewed.

[Twark_Main]

So what's the cost per seat (and per ton) again?

[DanClemmensen]

I suspect that my latest variation will require more fuel, but I should probably go to the effort to find out. I do find it interesting that SpaceX does consider at least one extra pass through the Van Allan Belts acceptable as a price to bring HLS back to LEO. Although initial mission will be crewless, follow on will be crewed.

I'm sorry, but I do not recall seeing any mission of this type described by SpaceX. We have a lot of speculation here on our forums which include such a mission, but the NASA HLS contract NextSTEP appendix H, Option A, and the extension to Option B) do not require a return of an HLS to LEO. If you have it, please provide a reference to a SpaceX proposal to return HLS to LEO.

[Roy_H]

I guess I need to clarify that this is not an official SpaceX plan, only a possibility.
Ok, again according to Grok.
LD has to be only 705 ton fuel capacity.
LD gets filled at 200km orbit, 5 ST flights.
LD burns to 10,000km x 200km orbit and gets topped off with 4 more ST flights (one gets partially filled from 3 more at 200km orbit then it flies to 10,000km x 200 km orbit to top off LD).
LD performs TLI to LLO
HLS is filled at 200km orbit, 8 ST flights.
Dragon meets HLS and astronauts transfer. Dragon performs EDL.
HLS flies to 800km circular orbit (below Van Allan Belt)
One more ST flight to top off HLS.
HLS performs TLI to LLO and gets fuel from LD to perform lunar landing payload drop off and return to LLO.
HLS gets more fuel from LD.
HLS returns to 500km circular Earth orbit.
LD returns to 5,000km x 200km HEEO
one more ST flight to LD adds fuel to return to 500km circular and later to 200km circular.
Dragon flies to HLS to return astronauts to Earth.

So this plan actually reduces the number of ST flights to 19 while the astronauts only have to pass through the Van Alan Belts once each direction.

One more Starship flight to 200km orbit is required outside of this basic flight plan. To deliver up to 100 ton payload or on initial flight to deliver add-ons to HLS and LD, namely MLI and active cooling solar panels and radiators. Of course this only has to be done once and the initial payload will be less than 100t leaving room for add-ons.

One less ST flight to 200km orbit is required on initial mission as HLS and LD arrive with residuals in their tanks.

[Roy_H]

I suspect that my latest variation will require more fuel, but I should probably go to the effort to find out. I do find it interesting that SpaceX does consider at least one extra pass through the Van Allan Belts acceptable as a price to bring HLS back to LEO. Although initial mission will be crewless, follow on will be crewed.

I'm sorry, but I do not recall seeing any mission of this type described by SpaceX. We have a lot of speculation here on our forums which include such a mission, but the NASA HLS contract NextSTEP appendix H, Option A, and the extension to Option B) do not require a return of an HLS to LEO. If you have it, please provide a reference to a SpaceX proposal to return HLS to LEO.

I'm sorry if I implied that this was in planning stages. This is just my speculation based on SpaceX requesting permission to fly HLS to Medium Earth Orbit for re-fueling.

[DanClemmensen]

I suspect that my latest variation will require more fuel, but I should probably go to the effort to find out. I do find it interesting that SpaceX does consider at least one extra pass through the Van Allan Belts acceptable as a price to bring HLS back to LEO. Although initial mission will be crewless, follow on will be crewed.

I'm sorry, but I do not recall seeing any mission of this type described by SpaceX. We have a lot of speculation here on our forums which include such a mission, but the NASA HLS contract NextSTEP appendix H, Option A, and the extension to Option B) do not require a return of an HLS to LEO. If you have it, please provide a reference to a SpaceX proposal to return HLS to LEO.

I'm sorry if I implied that this was in planning stages. This is just my speculation based on SpaceX requesting permission to fly HLS to Medium Earth Orbit for re-fueling.

OK, but please try to be more precise in your wording. I know that I am probably guilty of this same problem of miss-attributing stuff, but I try to avoid it. In this case you specifically asserted that "SpaceX does consider at least one extra pass through the Van Allan Belts acceptable".  In this era of AI, it is particularly important to avoid making unsupported assertions that  may be propagated.