The plan for SpaceX’s first demo in-orbit refueling mission of Starship
Link here The details come from a presentation at a public meeting by Amit Kshatriya, Deputy Associate Administrator of NASA’s Moon to Mars program, with this the key takeaway:
Kshatriya then expanded the discussion beyond the next few Starship flights and talked about the required technologies for a fuel depot in orbit and the in-orbit capabilities needed to transfer fuel. “We need an instance of the ship that is essentially long, has the endurance to stay in orbit long enough for the sequence to work.
“So, we need a ship that has at least three to four weeks of endurance in orbit. That endurance is gained through augmented power system capability, augmented battery capacity, full insulation of the cryogenic systems, vacuum jacketing of all the lines, et cetera, to make sure that the cryogens that are being stored or are meant to be stored don’t boil off.”
The challenges of a cryogenic ship in orbit include the need to prevent boil-off from the stack. To facilitate the journey to the Moon’s surface, Starship will have to be refueled. For this, the company plans to refuel a depot in low-Earth orbit (LEO), which would be resupplied by several tanker Starships. The HLS Starship would then dock with this depot before departing for the Moon.
To prove this system will require a Starship test flight that lasts several weeks in orbit, to prove the capability needed for a lunar mission. It will also require a refueling mission that will require several Starship/Superheavy launches, one to put the fuel depot into orbit, several more to fuel that depot, and a final launch of Starship for its refueling and endurance test.
According to the update, SpaceX is still aiming to be ready of the upcoming fourth Superheavy/Starship demo orbital flight in the first two weeks. The NASA official claimed it would occur no later than the end of May. I see that as a confirmation that NASA really doesn’t expect the FAA to issue a launch permit when SpaceX is ready, and that the permit might not arrive in time for a May launch. This statement is meant to soften the blow when the launch finally gets delayed into June, or later.
Whether the many required later Starship launches as described above can get FAA approval quick enough to prove out this system soon enough to meet NASA’s 2026 present target date for its manned lunar landing seems very unlikely. Moreover, even if it does it will be a major challenge for SpaceX to meet this schedule.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
Link here The details come from a presentation at a public meeting by Amit Kshatriya, Deputy Associate Administrator of NASA’s Moon to Mars program, with this the key takeaway:
Kshatriya then expanded the discussion beyond the next few Starship flights and talked about the required technologies for a fuel depot in orbit and the in-orbit capabilities needed to transfer fuel. “We need an instance of the ship that is essentially long, has the endurance to stay in orbit long enough for the sequence to work.
“So, we need a ship that has at least three to four weeks of endurance in orbit. That endurance is gained through augmented power system capability, augmented battery capacity, full insulation of the cryogenic systems, vacuum jacketing of all the lines, et cetera, to make sure that the cryogens that are being stored or are meant to be stored don’t boil off.”
The challenges of a cryogenic ship in orbit include the need to prevent boil-off from the stack. To facilitate the journey to the Moon’s surface, Starship will have to be refueled. For this, the company plans to refuel a depot in low-Earth orbit (LEO), which would be resupplied by several tanker Starships. The HLS Starship would then dock with this depot before departing for the Moon.
To prove this system will require a Starship test flight that lasts several weeks in orbit, to prove the capability needed for a lunar mission. It will also require a refueling mission that will require several Starship/Superheavy launches, one to put the fuel depot into orbit, several more to fuel that depot, and a final launch of Starship for its refueling and endurance test.
According to the update, SpaceX is still aiming to be ready of the upcoming fourth Superheavy/Starship demo orbital flight in the first two weeks. The NASA official claimed it would occur no later than the end of May. I see that as a confirmation that NASA really doesn’t expect the FAA to issue a launch permit when SpaceX is ready, and that the permit might not arrive in time for a May launch. This statement is meant to soften the blow when the launch finally gets delayed into June, or later.
Whether the many required later Starship launches as described above can get FAA approval quick enough to prove out this system soon enough to meet NASA’s 2026 present target date for its manned lunar landing seems very unlikely. Moreover, even if it does it will be a major challenge for SpaceX to meet this schedule.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
I am interested in the evolution of the “propellant economy” for inner solar system exploration. Initially it seems that propellant (fuel and oxidizer) is assumed to be provided from Earth, lofted into LEO by tankers and transferred to some sort of depot. Lunar-bound or Mars-bound ships would take on propellant from these depots.
The next step might be establishing depots in Lunar orbit, allowing maximization of payloads to and from the Lunar surface., and overall flexibility of operations.
But sustaining Lunar orbit depots from the surface of the Earth would be an expensive proposition, and sooner or later it would seem that in situ propellant production on the Moon’s surface would become very desirable.
I have not seen any detailed discussions of in situ propellant production on the Moon, only general statements that it is possible. It seems obvious that this capability is critical, given the shallow depth of the Moon’s gravity well compared to that of the Earth.
Not that many years ago, I recall that SpaceX seemed to regard the Moon (and especially the Lunar Gateway) as a distraction from its plans to colonize Mars. I wonder if that attitude has changed, not just because of HLS’s critical role in the return to the Moon, but because of the ultimate reality of needing to fill-up hundreds of thirsty Starships!
I think Space X said it would take something like 10 to 12 refuel flights to give the moon mission a full tank of fuel.
But they do not say of that is just using the left over fuel in the second stage or of they will be launching tanker ships with no cargo area and larger fuel tanks.
Really need a shield from the Sun. Perhaps something like the used by the James Webb telescope?
Ray,
It seems unlikely that there will be a single propellant economy for the entire inner solar system. I think there will be at least three.
One will be Earth-based and will deliver propellants to LEO depots that serve Earth-orbiting infrastructure of various kinds as well as vehicles looking to refill prior to departures for destinations in deep space. Such deliveries will, I expect, mostly be made by Starship tankers. These will initially provide LNG and lox for outbound Starships heading Moon- and Mars-ward. But I suspect SpaceX will be paid to develop – or at least launch – depots for other propellants wanted by other players and probably also modified tankers to haul them to orbit in quantity and at minimum cost. Hydrogen is one such possibility. Argon for electric thrusters is another. Even nitrous oxide and ethane may be in the mix at some point.
The second inner solar system propellant economy will be Moon-based. Exactly what it will be will depend on what is actually found in those shadowed polar craters. If water ice proves abundant there, hydrolox propellant will be straightforwardly possible. Water or not, though, it seems a lot of some hydrogen-oxygen compound is there so hydrolox still seems a good bet. Lunar smelting operations will produce huge amounts of oxygen as a byproduct and oxygen dominates the total mass of both hydrolox and methalox propellant mixes.
Making methane on the Moon requires carbon in addition to hydrogen and the Moon – at least the Earth-facing half – has proven to be quite carbon-poor. Perhaps that will prove less true of the lunar Farside. It may also prove to be the case that lunar carbon is concentrated around ancient impact sites of carbonaceous chondrite asteroids.
Given that there is likely to be a permanent imbalance of mass going to and coming from the Moon under propulsive power – people and freight will both require being propulsively landed, but only the freight will stay – perhaps a lunar methalox economy will be based on sending captured carbonaceous chondrite NEOs to lunar orbit and doing the methane synthesis there using oxygen and hydrogen sourced from the lunar surface. Bulk commodities such as these will most likely be launched, in quantity, using SpinLaunch technology which requires no propellant.
The third inner solar system propellant economy will be centered on Mars. Mars can easily be the source of vast quantities of methalox, hydrolox and argon propellants. Mars’s low gravity and thin atmosphere make Spin Launch technology a decent fit there as well, even if not as good a fit as on the Moon. Optimum sites for such facilities would likely be the peaks of one of more of Mars’s giant extinct volcanoes.
SpaceX has definitely gotten the lunar bug in recent years – while continuing to be as Mars-crazy as ever. There is a lot of expensive Starship-related infrastructure that it simply makes no sense to have idle during most of the 26 months between Mars Starship armada departures. Said infrastructure can be kept continuously busy supporting traffic to and from the Moon between major Mars pushes.
pzatchok,
The number of Starship tankers needed to refill a Moon-bound Starship has yet to be precisely determined, even by SpaceX. This is true not least because the type of mission to be performed by the Moon-bound Starship is also a variable that will affect the number of tanker-loads of propellant required for LEO refilling. A Dear Moon-class Starship looking to do a space tourism loop-around of the Moon on a free-return trajectory should need less propellant than would, say, the same ship carrying lunar surface-bound passengers to a lunar orbit rendezvous with an HLS lander. This mission profile, in turn, should require less propellant than a newly minted HLS lander bound for the lunar surface with enough propellant reserve to get back up to lunar orbit.
There is also the matter of Starship evolution to consider. Tankers based on Starship Version 3 technology should be able to haul twice or more the propellant load uphill as tankers based on Starship Version 2. Version 2-based tankers will most likely be what gasses up the LEO depot(s) used for early Artemis missions.
Dick, thanks for your insightful comments. My intention was certainly not to propose that there would be a single inner-solar system propellant economy, but rather to highlight the simplistic fixation to date on a refilling capability driven from the surface of the Earth, which is at the bottom of a very deep gravity hole! Every time a skeptic hyperventilates about the number of launches it will take to tank up a Starship, they make this assumption.
We need to constantly remind ourselves of the simple fact that once you are in orbit around the Earth, or even better in the neighborhood of the Moon, you have emerged from a deep hole, and have the inner Solar System spread out before you, at least metaphorically.
Even if Starship never finds a way to re-enter…the SH/SS infrastructure just made assembly of the craft from the old MARS ONE CREW MANUAL a lot more doable.
Rick Sternbach was working on a mock-up of the lander…
Ray Van Dune,
Here is a possible economic look, based upon Dick Eagleson‘s three-prong “propellant economy.” I base it upon this linked delta-v chart, which shows how deep the gravity wells are for various planets (note that Earth and Venus have atmospheres that require additional delta-v than gravity alone):
http://i.imgur.com/SqdzxzF.png
Better efficiencies are likely possible, but the basic economy would have expenses that look similar to the delta-vs needed to get around the solar system or around the Earth-Moon system. My analysis assumes that the relative delta-vs represents relative costs, the variable costs, and that the fixed costs of developing rockets and infrastructure eventually become second-order effects on these economies.
Earth-based:
This one is expensive, as the delta-v is 9.4 km/s just to get from the Earth’s surface to low Earth orbit (LEO). I suspect that this economy will not last too many decades, because other sources would take less delta-v to provide propellants to LEO. Delta-v from the Moon to LEO is 5.67 or less, if aerobraking can be performed without boiling off too much propellant, but no less than 2.55.
Moon-based:
Getting to the high lunar orbit from the Earth is quite expensive, so I expect that this economy will be quite strong, assuming there really is water on the Moon for use as propellants. Getting propellant to lunar escape velocity is 2.55 km/s, and an additional 0.09 to attain the rest of Earth escape velocity. This is significantly better than 12.61 for escape velocity from Earth’s surface.
Getting to L4 or L5 is similar to the escape velocities from both the Earth and the Moon. Moon-based propellant economy wins over Earth-based.
Spin Launch or mass driver technologies may make lunar orbit a more desirable re-tanking waypoint, saving propellant with the reduced number of reaction-propelled launches, using electricity instead of propellants, and presumably using less structural mass per ton of launched material.
Centered on Mars:
This analysis suggests that propellants from the surface of Mars may be more expensive than sending them from the Moon. From the lunar surface to Mars capture is 3.72 km/s, but it is 3.8 just to get from Mars to low Martian orbit. Propellants for low Mars orbit may be more efficient coming from Mars than from the Moon, so there is some amount of probable propellant economy at Mars, but this likely is not a good re-tanking port for travel around the solar system.
SpinLaunch or mass driver technologies may make Mars a more desirable re-tanking waypoint.
Another possible source of propellants could be the Asteroid Belt. At less than 3 km/s to Mars capture, a Mars centered economy may eventually get some of its propellants from the asteroids. Asteroids may be the waypoint to the outer planets and could be a source for the cis-lunar economy, especially if water turns out to be scarce on the Moon.
SpinLaunch or mass driver technologies may make the Asteroid Belt a more desirable propellant source.
The outer rings of Saturn probably won’t be a re-tanking stop for interstellar travel. It takes too much just to get back out, and it would take some amount more to get there in the first place. However, it might be worth looking into the outer moons.