> There are still major risks with the Starship program
To expand on this: I think it's reasonable to assume that the stack will reach orbit just fine and be a functional rocket.
The big risks are related to recovery. Starship will require in-orbit refueling to go to the moon, so (rapid) reusability is somewhat of a hard requirement.
Superheavy (the first stage) is huge and will land directly on the launch tower instead of using landing legs - to reduce turnaround times. This is innovative and completely unproven. And a RUD would at the very least put the launch tower out of commission for a while.
Starship (the second stage) will also have to survive the high velocity reentry in a good condition and nail the crazy landing maneuver. SpaceX heat shield tiles and the general aerodynamic and thermal properties of the rocket are an unknown for now.
Musk recently said that Starship will probably require "many test flight" to achieve successful reentry and landing.
On top there have been quite a few reliability issues with their new Raptor engine, which need to be ironed out.
I'm sure SpaceX will figure it out, but there are a lot of risks lurking in the development program.
All this makes the choice to go for SpaceX more impressive for the usually so cautious NASA.
But the payoff would be enormous. If the re-usability works out, Starship can completely change the game for the launch market and lift capability.
Many of these risks don't apply to the lunar variant. The lunar variant won't be launching people from earth and won't be returning to earth. No re-entry, no landing flip, etc.
As far as descent, it will do final touchdown with smaller engines higher up to avoid kicking up rocks. During landing, I think pretty much any one of the 6 raptor engines can be used to abort.
Why do you think they would need to do those launches in quick succession? If the lunar lander starship is parked in orbit without a crew it can be refuelled over any convenient period of time. Once it's fuelled just send up the crew in a dragon capsule and off you go. The dragon would probably make a good lifeboat if you brought it along for the ride somehow.
Also it does not need to be the same tanker to do the resupply. The plan is to make 2 starships per week. There should be plenty available to continue refuelling missions if one is not available.
Wikipedia[1] cites a 2010 study that gives a boiloff rate of 0.1% per day for hydrolox. Not sure if it would be less for pure LOX. Methane would remain stable so I wonder if there's a way you could balance the fuel load so that you can deliver only methane on some of the trips and then all the LOX in one trip to avoid having it hang around in orbit.
Oxygen is the vast majority of the propellant mass, I'm afraid. Methalox is CH4+2O2->CO2+2H2O, so you need 4 Oxygen atoms for every Carbon atom (with Hydrogen being a rounding error).
As long as the crewed starship is fuelled in orbit not too long after the last tanker ship launched, then the amount of boiloff will be negligible.
I suspect Spacex will develop cooling systems to re-liquefy any gaseous propellants as this will be more of a concern for the ~6 month mission to Mars.
Dragon is 4.4 meters (14.4 feet) tall and 3.66 meters (12 feet) in diameter. Starship fairing payload envelope is 22m tall and 8m in diameter. More than 3 dragons would comfortably fit inside.
I think the idea is that the fueled-up Starship in LEO would have already have most the payload inside since it launched. The only thing it would be lacking is the astronauts, so they can come in a much smaller vehicle.
That said, this contract has astronauts boarding Starship in lunar orbit, not Earth orbit.
In my opinion the way to think about SuperHeavy+Starship is a scaled up stainless steel Falcon 9. Currently Falcon 9's first stage booster (usually) lands and is quickly/cheaply refurbished/reused, while the second stage is completely thrown away except for partially successful attempts at fairing recovery. They've used this partially reusable system to do a large number of launches quite cost effectively.
In SH+SS, the "Starship" part is the second stage, with the revolutionary goal that it can deliver a payload to orbit and then skydive back to earth and propulsively land itself. That has major risks and is unlikely to succeed the first number of attempts, with the loss of the stage and the 6 raptor engines.
The "Superheavy" portion is very much equivalent to a scaled-up F9 booster, and the risks to landing it should be much lower (Elon's crazy catch ideas notwithstanding).
tl;dr I think Starship system can mostly work if it's partially reusable to a similar extent as F9. Losing a half-dozen second stages to do a full orbital refueling for a Moon or Mars mission should still be a fraction of the cost of a single SLS launch, and they can continue working on full reusability while performing missions and cashing checks.
> Superheavy (the first stage) is huge and will land directly on the launch tower instead of using landing legs - to reduce turnaround times. This is innovative and completely unproven. And a RUD would at the very least put the launch tower out of commission for a while.
I strongly suspect that they will be building many identical launch towers, it's pretty much their modus operandi and it makes sense. They've already had two Starships queued up at the launch pad for testing. Once they further improve the factory they'll probably need to build out more pads so they can keep the launch cadence up and free up space in the high bay. They're going to need to perfect that process if they are serious about eventually doing thousands of flights per year and sending hundreds of ships to Mars per conjunction. That's going to need a lot of Starships, a lot of launch pads, and probably several factories.
Well, they’ve got their two oil rigs, Phobos and Deimos, which I believe are to be the launch/catch facilities, so that’s two for starters. I don’t know if they’ll be doing it on land at all, or if the intent is to launch from one and catch with the other, allowing more downrange capability. We’ll see - it’s a blast (boom boom (boom boom!)) watching their development process.
SpaceX is asking the EPA for permission to build a second orbital pad and tower in Boca Chica, and I'd assume that we might hear something soon about the mothballed 39A Starship launch mount
> Starship will require in-orbit refueling to go to the moon, so (rapid) reusability is somewhat of a hard requirement.
Is it though? The lunar starship itself doesn't depend on reusability. If SpaceX cannot get reusability down, they'll have to expend a few boosters and tankers to get it working. That'll cost them their profit, but it would fulfil the contract.
Second stage tanker build costs are estimated at around $30M. Expending a dozen would thus cost $360M, about 15% of the contract. I highly doubt that SpaceX set their profit margin lower than 15%.
I'm getting very nervous about manned propulsive landings. I know it's been done before, e.g. the LEM, but that at least had an abort option available and the flip manoeuvre seems to introduce a lot of unpredictability into the process. I wouldn't be surprised if they take up a Crew Dragon with them in a cargo bay to bring the crew back down separately for the first manned flights, until they've demonstrated a strong track record of successful propulsive landings.
As for Lunar Starship, it's massively overengineered for the Artemis requirements, capable of taking 100 tons to the Lunar surface. That's great for later missions to set up a base, but even then you'd likely need a crew version just for shuttling people back and forth. So I wouldn't be surprised to see the first version of that to be somewhat scaled down from the concept art. That should massively reduce the number of refuelling missions needed for the early Artemis flights.
> I'm getting very nervous about manned propulsive landings.
Humans will land on earth in Orion capsule not Starship. So there will only be a tanker that has to do the flip.
On the moon, there is no flip.
The Appollo didn't have a abort option is parts of the flight, unless I am misinformed.
> So I wouldn't be surprised to see the first version of that to be somewhat scaled down from the concept art.
The problem is then about how you do the integration. All the tooling and processes are designed for one size of Starship, to change the whole design just to make it smaller is unlikely to be an efficient thing to do.
Instead they could just fly part of it empty and take far less then the full 100t to the moon, rather then design a smaller version.
If a LEM landing became untenable they could abort to Lunar orbit by launching the crew capsule. You know how after landing on the moon the way they got back to Lunar orbit was by launching the crew capsule, using the lower stage of the LEM as a launch platform? They could actually do that in flight. You're right of course though, I forgot that for Artemis they wont be landing people on Earth in Starship.
All they need to do to make a lighter Lunar starship is make it shorter. Just miss out some fuel tank and payload section segments. No need to make significant changes to the functional parts, it would just be stubbier.
I didn't know they could actually do the accent in flight. Do you have a source about that? Apollo is seriously insane, they thought of everything and pulled it off.
the next morning after the first such delivery would feel like a new era because with Starships it will be just like a regular shipping line, less than $1B per 100ton cargo to the Moon taking just several days. The Moon will become more reachable than Philippines were at the time of Manilla Galleons (which would be more like the Mars flights).
I agree, Crew Dragon (and maybe Orion and Boeing Starliner) are going to be the people-carriers of choice for Earth launch and re-entry for at least the next decade.
I think people are really vastly underestimating how fast things are moving. I think you're completely wrong and Crew Dragon will be relegated to only fulling a remaining portion of a NASA contract after less than 5 years. Everyone else (private astronauts) will fly on Starship.
Yeah, I really can't help but wonder if SpaceX is going to go after the long distance travel market. Starship can do suborbital hops without Superheavy.
Only comparatively short ones, with limited payload. Getting to a ballistic trajectory from one side of the planet to the other takes almost as much dV as going to orbit.
To expand on this: I think it's reasonable to assume that the stack will reach orbit just fine and be a functional rocket.
The big risks are related to recovery. Starship will require in-orbit refueling to go to the moon, so (rapid) reusability is somewhat of a hard requirement.
Superheavy (the first stage) is huge and will land directly on the launch tower instead of using landing legs - to reduce turnaround times. This is innovative and completely unproven. And a RUD would at the very least put the launch tower out of commission for a while.
Starship (the second stage) will also have to survive the high velocity reentry in a good condition and nail the crazy landing maneuver. SpaceX heat shield tiles and the general aerodynamic and thermal properties of the rocket are an unknown for now.
Musk recently said that Starship will probably require "many test flight" to achieve successful reentry and landing.
On top there have been quite a few reliability issues with their new Raptor engine, which need to be ironed out.
I'm sure SpaceX will figure it out, but there are a lot of risks lurking in the development program.
All this makes the choice to go for SpaceX more impressive for the usually so cautious NASA.
But the payoff would be enormous. If the re-usability works out, Starship can completely change the game for the launch market and lift capability.