Actually it doesn't save them anything, in fact using densified propellant where it's not actually needed to get sufficient performance for the mission (i.e a ISS launch) will cost more in fuel as SpaceX always fully fuels the rocket even if all that fuel is not needed (provides margin in case of issues and for landing the rocket)
Arguably it'd be riskier to use non densified propellants for these missions as then they'd be using different procedures than the cargo missions they launch regularly and will have less experience with it and opportunities to find and fix any issues on a cargo mission before it affects a manned one.
SpaceX has been using supercooled propellants (and "load-and-go") for every launch since early 2016, including NASA cargo launches. It's been used over thirty times by now. Whatever additional assurance that NASA's advisory board wants, another few launches are unlikely to provide it.
Depends on the procedure they ultimately decided to use for the prep. Originally the the shuttle main engines had to be taken apart, with every part inspected before the next launch. If they have to do something like that there's not much point.
But if they can get it to point where it's a matter of gassing it up for the next flight, that's a huge savings. Fuel is a few hundred grand for a rocket that costs sixty million dollars. It's nothing, basically.
NASA isn't stupid, they know that if SpaceX manages to get rocket reusability they'll save a lot of money which would otherwise be spent on rocket launches.
I've also heard that fuel is not the main cost contributor to a rocket launch. In fact, it is a really insignificant portion of the cost. It is the vessel that contains giant amounts of fuel that is costly. Hence reusability from SpaceX makes sense and so does launching the rocket from high altitude to avoid building the first stage all together.
SpaceX just launched a shuttle into orbit that had a 1 second window for launch. They had zero extra fuel on board. It had 2 passengers and room for 2 more.
It's not ridiculous at all to think that they'd fuel a supply ship with exactly the fuel it needed and not more, and that that supply ship might have some empty space in it, especially if it were very, very large.
SpaceX’s BFR plans to overcome the propellant problem for getting to Mars by refueling in orbit. I am surprised the article didn't mention the refueling possibility. Maybe NASA didn't want to admit they are making a mistake putting all their cash into the SLS.
Also, the economic implications of the equation don't matter so much when you have a reusable rocket, and the BFR is supposed to be able to reuse both stages.
If running out of stored hydraulic pressure is the only problem they had, that's good. That's easy to fix, although it means some weight penalty.
What SpaceX did was a low-cost test. They were paid for a shipment to the ISS, which was successful. The test of the booster recovery system didn't cost them a launch. They didn't expend a booster just for this.
Access to orbit is a requirement for our current level of technological civilization.
SpaceX's launch capability is not only much greater than that of competitors (including states), they're using methane fuel and do not use solid fuel boosters.
For context, ESA's Ariane 5 uses solid fuel boosters (ammonium perchlorate, aluminum, hydroxyl-terminated polybutadiene) and a liquid fuel second stage (monomethylhydrazine, nitrogen tetroxide). NASA's SLS uses solid fuel boosters of the same composition and Ariane 5's. So does JAXA's H3.
If, as a species, we're going to be launching things into orbit, doing so using the SpaceX's tech is significantly cleaner than what we're using today. That's true even before considering reuse.
Yes, the article lists a few reasons, none of them convincing. Specifically:
> You have to get the propellant into space. This is going to take a large number of flights (~15) at a pace that has not been done before for a vehicle of that size (a launch every six days)
SpaceX has done 2 Falcon 9 launches in 1 day, and they would have done 3 if the third one had not have been scrubbed [1]. I really don't think that launching Starship is going to be any different, especially as it was specifically designed for reuse, unlike Falcon 9.
> You need to launch at pace because otherwise the propellant will boil off, which is another issue - you need to shade or insulate the propellant for a much longer period of time in much harsher conditions
First part is same argument as above. Second part (shading) - again, I don't see why it is harder than other hard things. Just add more insulation. Possibly do some passive or active cooling.
> There is no gravity: whereas on earth the propellant separates relatively cleanly into liquid and gas this isn't the case in space
Very similar problem to how you feed liquid propellant into a rocket engine when it relights in zero gravity. You use a small ullage thruster for this.
There's no real reason to stop using SpaceX and ULA unless they're going to start sending MUCH more to the ISS than those rockets can handle. SLS is really expensive per launch.
That's a good point, but then it is an odd thing for them to care about the fuel savings vs. their claim of not needing the first stage and allowing for single stage to orbit with a plane type launcher, which is a far bigger deal in terms of cost savings.
E.g. consider that Musk a few years ago estimated the fuel and oxidizer costs for a Falcon 9 v1 at ca $200k per launch, with a list price for the launches at $54m to $59.5m. Cutting the cost of the rockets themselves on the other hand, whether by reuse or making them smaller/cheaper will matter much more.
I guess whether eliminating the first stage entirely vs. reuse will matter much will depend on how many times recovered stages can be reused and how much it will cost to prepare them for reuse, as the potential fuel savings are basically rounding errors.
Reusable SpaceX rockets have 30% small payload compared to non-reusable ones, as they have to carry extra fuel for landing.
Catching the rocket instead of landing it could be significantly more efficient as you wouldn't have to carry much more weight except for the parachute.
It seems to me there is a reasonably low cost solution to demonstrate safety: SpaceX should load and unload the fuel multiple times for its human-qualification spaceflights. If SpaceX is correctly confident fuel loading is safe, the extra handling won't result in incidents. This would be a fairly minor expense given nothing is consumed or destroyed -- just handling costs and incidental losses due to evaporation and so on.
SpaceX has built part of their business around the idea that it's worth trading a moderate amount of payload for re-usability as long as they can still reach the orbit their customers care about and it was considered an extremely risky bet before they made it routine.
It doesn't make fuel cheap, let alone very cheap.
Actually another significant part of SpaceX business is modern engineering and modern mean of production. They used to launch without recoverability for some high orbit payloads and they were competitively priced for that too.
If you want to send up more propellant, you need to send up even more propellant to get the propellant you want up to space. Which means you have no room left for your actual payload.
Back in 2013, before SpaceX had recovered any rockets at all, Elon Musk talked about how the way they were going to get reusable rockets was by making the rocket and the reusability more efficient: https://youtu.be/vDwzmJpI4io?t=26m30s
True. Another thing that I keep thinking is that currently the first stages of the rockets are not reusable. Even if they have to build a new starship per flight, they can just reuse the boosters and still be miles ahead of anyone else, with a Saturn V sized rocket ready to launch.
Plus they can expand the real state in the ISS much cheaper by just docking and leaving it there.
There's a reason we don't throw away a 747 after one flight.
Fuel is only a couple percent of the cost of a rocket launch. Rockets are expensive, and on the Falcon 9 the first stage is 80% of the cost of the rocket.
In the early days of SpaceX I saw claims that expendables were more economical because you could build them cheaper, but then SpaceX went and build reusable rockets that are also cheap; their rockets cost less than competitors even without reuse.
They're getting government business because they charge the government less than their competitors charge. The subsidy argument doesn't make sense unless it's only the commercial launches that are cheap.
There are a lot of vested interests in this industry that are strongly incentivized to say reusable rockets are no big deal. I think they'll continue to say that until the BFR flies and SpaceX drops their rates to levels far below what disposables could ever achieve.
Yeah, and with much higher required dv and more required stages this would be a huge problem. But we only need two stages to orbit when launching from Earth, so it's really not that big of a deal, and it turns out that optimizing for reusability ends up being a lot cheaper than optimizing for minimum fuel use. For example, it only costs $200k for a fuel load of Falcon 9 fuel. If you got rid of reusability you'd need less fuel and could save tens of thousands of dollars ... but at the cost of needing to build a new $54M spacecraft with each launch. Clearly that trade-off isn't worth it.
Arguably it'd be riskier to use non densified propellants for these missions as then they'd be using different procedures than the cargo missions they launch regularly and will have less experience with it and opportunities to find and fix any issues on a cargo mission before it affects a manned one.
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