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They somewhat apply because the lunar variant still needs to be fueled up in LEO with ~ 6 additional launches , all in relatively quick succession. This seems
by the_duke 6y ago
They somewhat apply because the lunar variant still needs to be fueled up in LEO with ~ 6 additional launches , all in relatively quick succession.
This seems unfeasible without rapid reuse actually working.
- russdill 6y agoTrue enough, they can't be throwing away tankers for each refuel.
- garmaine 6y agoAt the price NASA is willing to pay, they can. The tankers are only a few million dollars in raw materials.
- themgt 6y agoIn 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.
- jacquesm 6y agoFairing recovery has been abandoned.
- andrewcchen 6y agoFairing recovery is not abandoned, they decided to fish them out of the water after a soft landing instead of catching them with a net.
- jacquesm 6y agoAh yes, right you are, it is the catching that they have abandoned. Thank you for the correction.
- pharke 6y agoWhy 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.
- NortySpock 6y agoThey may have solved the LOX boiloff problem, but perhaps not.
- cookingrobot 6y agoEven if they need to refuel quickly, why not launch 6 starships for that mission? They’re planning to build lots of them aren’t they?
- jsmcgd 6y agoAs 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.
- pharke 6y agoWikipedia[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. [1] https://en.wikipedia.org/wiki/Propellant_depot#Feasibility_of_propellant_depots https://en.wikipedia.org/wiki/Propellant_depot#Feasibility_o...
- laverya 6y agoOxygen 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).