Starship offers much potential for large payload delivered to Lunar surface but it is not human rated yet which may take a few years
Editor's note: The column is originally published on The Space Review and is republished here with permission. Any edits have been made for clarity and style.
Eric Berger reported on December 4 that NASA may cancel the SLS with the chances of cancellation being 75-25. Under the new administration and DOGE, the chances of cancellation may have only increased. We have to then look at other options to put Americans on the Moon as soon as possible. Yes, those at the table, write the rules.
This method maybe the least costly, safest with margins and the quickest method to counter China.
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Griffin and Porter proffered an interesting and promising solution for returning Americans to the Moon more quickly than the present Artemis schedule. It describes sending Lander and Orion separately over a week to LLO (Low Lunar Orbit), docking there and landing 2 astronauts on Lunar surface using the Lander a la Apollo. This author feels that SLS is not a sustainable or cost-effective approach for boosters, hence here we intend to modify it by using Falcon Heavy instead of SLS as booster. The rest of the ideas, the maneuvers for human landing on Moon remain the same, except that the upper stages taken to Lunar surface offer another repurposing potential.
Starship offers much potential for large payload delivered to Lunar surface but it is not human rated yet which may take a few years. Another issue is a large refueling need (from 8-16-20 flights as per SpaceX-GAO-NASA numbers) which makes its reliability questionable at best as described in Griffin-Porter paper.
The reason, upon calculations, is the very high Dry Mass (DM) of Starship (the upper stage) at almost 100 t.
With Blue Origin's (BO) Blue Moon MK II Lunar lander in the 45 t range (wet mass) which can take 4 astronauts to Lunar surface from NRHO and hence from LLO, it also offers an enticing possibility of these two Space companies partnering for the sake of the country. Four flights of Falcon Heavy with its upper stages docked in LEO would give enough DeltaV for TLI and LOI. Blue Moon though rests on BO successfully developing solar powered LH2 refrigeration scheme to have the cryogenic propellants, especially the LH2 storage near 20K for the period mentioned by them - 30 days. Also there would be no need for a tug or refueling at NRHO.
China's Chang'e 4 landed on the Farside of the Moon in January 2019. Chang'e 5 did so in December 2020 and returned samples from Moon surface. Now, Chang'e 6 recently returned the samples from near the South pole, a very attractive site for any future habitation and in situ resource utilization, with possible indication of copious amounts of water-ice, a crucial element for any Lunar program. China will establish a permanent presence on Moon through the International Lunar Research Station (ILRS) shown here by 2030, with Taikonauts on Moon likely sooner than that. Would China stake a claim to the entire South Pole as some have mentioned? No, but they can and will do so for the most promising regions there.
Starship is a very promising possibility, though with two caveats. The Dry Mass of the Starship (the upper stage) is too large for Lunar missions while being necessary for the Mars mission - its primary intention. Its reusability for Artemis III mission is not of primary importance, neither is that of the Super Heavy booster. The problem here is the Dry Mass at nearly 100 t. This then, and hence, require 8-20 refueling tanker flights for the DeltaV requirements of Trans Lunar Injection (TLI), Lunar Orbit Insertion (LOI) and Landing. Refueling in LEO will require many test flights to increase the TRL to a satisfactory level, whereas, docking in LEO, as proposed herein, has been done since 1965, manual as well as automatic. If SpaceX were to develop a smaller version of the upper stage for Moon and CiSLunar, it would be appropriate to look at that option but at this stage, we need to look at other possibilities.
That option would be using Falcon Heavy instead - a proven vehicle with 8 of 8 successful flights under its belt. The computed numbers below prove that this is quite feasible with margins to spare. Although 3 docking in LEO would be required for the Orion, there is no refueling need and it is a much smaller number than the Starship HLS refueling estimates. If SpaceX designs an upper stage with much lower DM, it will change its potential for use as Lunar Lander which will significantly improve its potential as HLS. With China making big strides, the time also become of essence.
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Boil-off issue:
Since this proposal uses the upper stage (US) of Falcon Heavy using Merlin 1Dv, there would be no LH2 boil off issue either, unlike if were to use Centaur III or BE-7 as offered by Blue Origin for Blue Moon and the tug. There would be LOX boiloff issue but it is much less severe compared to LH2. Also there would be no need for separate LOI stage (Centaur III) as described in "Returning Humans to Moon" by Griffin and Porter. The docked upper stages of the F9H will do the work of TLI plus LOI.
Architecture (Lander):
Lander would have to be built by NASA a ka the Apollo 17 Lunar Module called Challenger which carried 2 astronauts to the surface from LLO. It had a mass of 16.5 t so the new one here is bookkept at 18 t wet mass including higher consumable for 6.5 day stay. This would require 1-2 years to have it ready. The Lander uses MMMH/N2O4 as propellants so there is no boil-off issue.
Lander first: The campaign would then start with first Falcon Heavy flight carrying the 18 t Lander to LEO and park it there. Two Upper Stages (US) of Falcon Heavy (F9H) dock in LEO after 2 flights of F9H over perhaps a total of 24 hrs (one day).
1. F9H LEO payload is 38/54/63 t depending on fully reusable (FR), partially reusable (PR - the side boosters do RTLS and can be reused with the core expended), and fully expendable (FE). This analysis picked PR option.
2. One of the US carries the Lander as payload (~18 t) whereas the second one would carry that much (54 t) extra propellant which will remain in it at LEO.
3. Thus the PF is increased to what is required (0.7 for Merlin1Dv engine) for TLI plus LOI (3200+900 m/s) for the combination
4. The US Dry Mass is 4.5 t for F9H. Let us allow for beefing up the tanks (as we may use them for habitats on Moon also - or may not but the allowance is made in this analysis) and landing legs, thus adding another 1.5 t to DM
7. PF of the combination thus is 0.75 which is sufficiently greater than needed for TLI+LOI (0.7)
8. The combination fires the two of the US Merlin 1Dv rockets to do TLI and LOI capture (any combination that makes sense can be allowed - TBD).
9. The propellant used up will be 70 t. Total left over propellant in LLO is 20.8 t which is more than enough for landing the stages on South Pole. This maneuver takes 3-5 days.
10. The side US's (6 t each) separate in LLO and each one lands on Moon using the landing legs using ~5 t propellant (PF for the landing is 0.44 for 2000 m/s DeltaV)
11. One could possibly postulate the use of US tanks (already beefed up and with windows) as potential habitats. They can be vented to Space first and also can be later fitted with Bigelow habitats
12. The Lander remains in LLO waiting for the Crew module (Orion) to arrive.
13. The same procedure is repeated from Earth for the Crew using Orion (28 t) after the Lander is safely in LLO but this time with Three F9H flights over 48 hours.
14. Note that the TLI capacity this way is higher than that of SLS Block 2 (Crew Variant) and it would be easier and cheaper to do than SLS.
15. The Lander and Orion dock in LLO and the two crew transfer to Lander (Artemis III plan). The Lander Descent Stage takes the crew to Lunar surface.
16. After the anticipated stay (1 week?) the Ascent Stage of the Lander takes the crew back to LLO where it docks with Orion and transfers the two crew to it. Orion performs TEI burn and heads to Earth with all 4 crew.
17. All remaining procedures would be same as what would have been done with SLS in Artemis III.
* 2 SLS =~ $2 B each (IG # which does not include Orion, Centaur III) =~ $4 B. (IG estimate for all included is ~$4 B each flight)
* Substantial cost savings to NASA - almost 85%
This Modus Operandi is ALSO suggested for our future. The combination/permutation with four degrees of freedom (# of flights, # docked v refueled, payload sizes, and DeltaV needed for different destinations in Solar System provide hundreds of possible solutions with already developed/built rockets and engines. No need to redevelop new rockets for new aims except in specific cases.
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