22 thoughts on “NASA Has Selected Its Lunar Lander”

  1. I’m still awaiting the decree from NASA’s Director Nominate Bill Nelson that the Starship lunar lander must launch from atop the SLS….

  2. I have some doubts and would need to see more engineering numbers. Starship doesn’t have a high enough delta V to get go from LEO to the moon and back to LEO without aerobraking at the end, and even then it’s not going to have much margin, so payloads would be pretty small. Last year I shifted the refueling point to a GTO orbit and the payloads were huge, but the required refueling as problem because Starship doesn’t have a significant fuel payload to GTO. It’s GTO payload is about on par with a Falcon 9, due to it’s low mass ratio upon reaching low Earth orbit.

    A big driver of the numbers is trying to get a Starship off the lunar surface and back to LEO, which takes a mass ratio of about 2 with aerobraking on return, and about 4.5 to 5 without aerobraking. It has to aerobrake because Starship doesn’t have enough delta V to do the full round trip on propulsion alone. Staging the missions at a much higher orbit would solve the problem but, as I said, shifts the burden to the refueling missions.

    Using a Starship as a one-way lunar deliver of course avoids the issues and allows huge payloads, which could include a smaller and lighter return craft.

    But going through all the complexities of the possible modes, architectures, and comparing the payloads, launch requirements, and the financials would take quite a while, and require information that isn’t readily available.

    But Starships capabilities and costs make it light years ahead of any competition, so even a horribly non-optimal Starship solution is going to beat a highly optimized alternative architecture that uses RS-25’s or RL-10’s.

    1. Using a Starship as a one-way lunar deliver[er] of course avoids the issues and allows huge payloads, which could include a smaller and lighter return craft.

      Like a Crew Dragon knock-off with a beefier heat shield and with a vacuum Raptor in an extended Service Module you push out the nose of a Starship for the return leg? Leaving behind the Starship as a base module? I suppose that could be done.

      Staging the missions at a much higher orbit would solve the problem but, as I said, shifts the burden to the refueling missions.

      Like at GTO? Is it possible to do a highly eccentric Molyna type orbit in the cis-lunar plane for tankers? Would there be any benefit of that?

      1. The orbital mechanics is easy. The problems are centered on launch sites vs. land overflights. LSS and the tankers can fly out of Starbase (Boca Chica) and KSC (there’s a stub of a Starship/SuperHeavy pad there already) and fly through the Van Allens because they’re crewless. And remember the lunar orbital plane as seen from the earth ranges between +/- 28deg to +/- 18deg over a period of 9.3 years.

    2. Starship doesn’t have a high enough delta V to get go from LEO to the moon and back to LEO without aerobraking at the end…

      Is that the plan? Why go back into LEO? Why not just come all the way back to the surface of the earth?

      1. Lunar StarShip isn’t designed for Earth entry or landing. Once launched, it is restricted to vacuum. That’s where you can pick up a lot of weight savings vs. a stock StarShip. These savings may be more than offset by the bank of high-mounted engines necessary to take off and land without making a new crater, however.

        I still think it’s an open question as to whether StarShip will be the be-all-and-end-all spaceship. It is optimized for EarthLEO (with help from SuperHeavy to go up) and MarsLMO (by itself). It is designed to deal with their gravity, and their atmospheres. It is absolutely not the optimal design for long-distance/high-dV travel in outer space.

        Elon, when asked, has appeared willing to absorb the costs and inefficiencies of this leg of the journey, because StarShip is so darn useful–even *necessary*–to dealing with takeoffs and landings in atmosphere and “high” gravity, and because focusing on the singular design at this stage greatly reduces program risks. However, in the long run, if sufficient propellant can be manufactured on Mars, I have to question whether it would make more sense to establish a fleet of Mars-optimized ships, a fleet of Earth-optimized ships, a fleet of Moon-optimized ships, and a fleet of space-optimized ships (or even two: one for passengers, and one for bulk cargo/fuel between LEO and LLO or LMO). They’d have to figure out how to transfer the cargo efficiently from one ship to the next, but I suspect that is very solvable given the current state of robotics (see: Canadarm).

        1. Hrm. Should have paid closer attention to the preview. Double-ended arrows between Earth-LEO and Earth-LMO got recognized as HTML tags (Me smart. Me no dumb).

        2. “I have to question whether it would make more sense to establish a fleet of Mars-optimized ships, a fleet of Earth-optimized ships, a fleet of Moon-optimized ships, and a fleet of space-optimized ships”

          Isn’t that what they are doing with Super Heavy being the constant?

          1. Not yet. So far, SpaceX has announced the passenger/cargo base variant, the deployable-cargo variant (the “chomper”), the tanker variant… and now Lunar StarShip, which might turn out to be less of a variant and more of a Moon-optimized new design. None of them, however, are optimized for space travel per se; the first three are optimized for Earth launch and landing, and while not highly-optimized for Mars, are more than adequate for the job. What they’re not optimized for, however, is interplanetary flight; they’re far heavier than a ship optimized for deep space would be (because it would never leave vacuum).

    3. Another scenario to look at:
      A Starship lander and tanker are both fueled in LEO. The tanker parks in lunar orbit to meet and transfer fuel to the lander for the return trip. Lunar Orbit Rendezvous can save a lot of propellant over carrying all you need for the return trip down to the surface.

    4. I keep seeing this reference to refueling in “a GTO orbit,” and wonder whether the author actually means “GEO.” I can’t fathom the architecture of rendezvous in a geosynchronous transfer orbit, say 300 x 42,164 km, at some weird inclination. GEO is much better defined:
      42,164 km radius, zero degrees inclination. It does, however, require more delta V to get there from, say, the Cape, than is required to go from the Cape to the Moon.

      Please elaborate…

      1. I don’t think you want to diving through the Van Allen belts twice on every orbit. So I would vote against 300 x 42,164 km.

      2. I think GTO is being misused as a stand in for highly eccentric earth orbit (HEEO). The tanker and LSS would proceed to whatever HEEO in tandem and start the refueling as soon as the propulsion terminated. So no multiple orbits, it would take place during the ascent to apogee.

        It’s also important for people to remember where the Moon is. It doesn’t orbit over the equator, but just off the plane of the ecliptic, with the earth tipping up and down underneath with its obliquity (so the Moon behaves like it’s in a separate solar orbit, not like a satellite orbiting earth). The Apollo missions were timed so they could head for the Moon while bipassing the worst of the Van Allen belts (going over them, in most cases).

  3. “He believes an important step for NASA would be to commit to not just “visiting” the Moon but staying. “Having a policy in place that says the United States is committed to human permanence on the Moon would give commercial companies the confidence to invest,” he said.”
    Well, I am against this as general idea, as I think Mars exploration is quite important. I think not just important in terms of Mars, but important for the Moon and Earth. Or Mars allows fastest route to humans becoming a spacefaring civilization.
    Granted I don’t know if human settlements on Mars “going to work” {and don’t know if lunar water is mineable- which also tie in becoming spacefaring civ, and whether Mars could have human settlements be viable within short period of time [decades]. Or what critical is price of electrical power in space- how soon can it get to say, $1 per kw hour. {or only hundred times more expensive than earth electrical costs.
    But anyone, there certainly a possibility NASA could remain focused on the Moon, but I think within 5 years of landing on Moon, NASA should doing major levels of exploration of Mars.
    Or NASA should have a focus of doing as much Mars exploration which will “create an environment” in which Musk effort of settlements of Mars are not inhibited {or people will die settling Mars, and let’s do thing so have less people dying}.
    Or starship is really about Musk starting settlements on Mars.
    I think might better for Musk to focus a bit more on Moon- perhaps get more distracted with lunar potential. But getting settlement on Mars as soon as possible is pretty important.

    1. Why not both?

      Musk can have some of his people focus on lunar stuff with NASA while also keeping his focus on Mars. Maybe Musk will be ready for Mars at the same time NASA is and depending how things play out, NASA might be able to devote effort to both destinations.

      For SpaceX, I think the danger is how diversification of products could increase their operating costs and prevent them from offering prices low enough to make Mars an option for non-state customers. But then again, maybe we need someone(s) else to pick up the slack. SpaceX can’t do everything.

      1. –wodun
        May 6, 2021 At 4:54 PM
        Why not both?

        Musk can have some of his people focus on lunar stuff with NASA while also keeping his focus on Mars.–

        Well, if Musk focuses on making Lunar swimming pool, that would be good.
        I don’t think it has to cost a lot the money to mine 2000 tons of lunar water.
        So low pressure dome, and water at 5 C, and very deep pool.
        So 10 meter deep on Earth 1 atm, 10 meter on Moon, 1/6th atm.
        If have the dome hold as much as 1/2 psi, then water can be 20 C.
        Making 2000 tons rocket fuel would require a lot energy.

  4. NASA was spinning its wheels and still would be if Musk didn’t decide to push forward on his own ambitions.

    It will be neat to see how things develop over the next few years.

  5. The idea that LSS will go from LEO to the lunar surface and back to LEO comes entirely from nonsensical speculations on the NSF fora. The actual “plan” is to launch LSS to LEO uncrewed, refuel there and then fly to NRHO, pick up a crew, land on the Moon, then fly back to NRHO. That’s all. The $2.89bln buys two test flights, one crewless, the other crewed. There’s no particular expectation for what will happen to the two LSS vehicles after that. NASA will be putting the next phase (regular crew and cargo deliveries to the lunar surface from NRHO) out for bids.

    It’s an open question whether it’s cheaper to refuel and resupply a used LSS in NRHO or simply use a new one every time. The actual cost of a new Starship (e.g., outfitted as a tanker or satellite LV) is guesstimated at around $30mln apiece. Crew ships will obviously cost a bunch more, but maybe not so much it won’t be economical to simply throw them out after one use (and SpaceX owns them afterward, so…).

    The questions revolve around how much it will cost to refuel and reprovision an LSS in NRHO. It will take at least two standard Starship flights (one freighter and one tanker) to manage it, with each of those requiring some number (5 – 7?) LEO tanker launches per mission. That would be maybe 14 (+2 Starships) tanker flights per reuse, vs. 7 (+1 LSS) tanker flights per expendable mission. We won’t find out the details for a while yet.

      1. I need to start looking after myself better, as I sure do want to see what happens over the next several years. I’m 70, but my Dad lived to be 87. This is like waking up to find yourself 70 years old in 1960. Poor Willy Ley died on June 24, 1969, aged 62…

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