[HN Gopher] NASA's bet on Starship for the Moon
___________________________________________________________________
NASA's bet on Starship for the Moon
Author : alexrustic
Score : 143 points
Date : 2021-04-23 14:39 UTC (8 hours ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| Nomentatus wrote:
| This isn't a "bold bet", it's a backstop. It's what (little) the
| Senate will pay for right now. Their one choice. It helps ensure
| that NASA has at least one way to get large amounts of cargo onto
| the moon. No actual manned flight is included, and personally, I
| don't expect Starship to be man-rated soon, or - perhaps - ever.
| It's not needed for the most dangerous task, which is getting
| astronauts up to orbit, that's already possible via Dragon.
| Avoiding putting kerosene soot into the stratosphere is the only
| reason to prefer sending astronauts into orbit via Starship.
| skissane wrote:
| > It helps ensure that NASA has at least one way to get large
| amounts of cargo onto the moon. No actual manned flight is
| included, and personally, I don't expect Starship to be man-
| rated soon
|
| That's not true. SpaceX's bid includes at least two lunar
| landings - at least one uncrewed, and one crewed. (They may
| have to have more than one uncrewed landing if things
| unexpectedly go wrong with the first one.)
|
| For the crewed landing, Starship will launch from earth, be
| refuelled in LEO, then travel to lunar orbit and wait there. Up
| to 3 months later, Orion will launch on SLS with four
| astronauts and also travel to lunar orbit. Once in lunar orbit,
| Orion and Starship will rendezvous and dock, and two astronauts
| will transfer to Starship (the other two stay on Orion).
| Starship will land those two astronauts on the moon, and then
| re-dock with Orion, and the four astronauts will use Orion to
| return to earth. The Starship will be disposed of, probably by
| landing it again on the Moon's surface, where it will await
| possible future reuse by a lunar base. (Ideally it would be
| reused multiple times before disposal, but I don't think that's
| going to happen at first - how do you inspect/repair it in-
| between uses if it can't return to Earth?)
|
| Starship is not being crew-rated for launch and re-entry as
| part of this contract, although that is the long-term goal. It
| is only being crew-rated for in-space use and the lunar
| landing. Orion will be the vehicle used for crewed launch and
| re-entry for lunar missions initially. Once Starship is crew-
| rated for launch and re-entry, that may change.
| larrydag wrote:
| Does this mean that the Lunar Gateway project will be scrapped?
| https://www.nasa.gov/gateway
| Diederich wrote:
| It's mentioned in your link, but I'd like to call it out more
| clearly: NASA has also recently selected SpaceX to be the sole
| launch provider for the initial Lunar Gateway, and the sole
| launch provider for resupplying it as well.
| wmf wrote:
| The current official plan is for Starship to take astronauts
| from the Gateway to the surface of the moon and back. That plan
| is ridiculously complex and expensive when you could skip the
| Gateway and ride Starship all the way to the moon instead. At
| some point Starship will be ready and SLS and the Gateway will
| still not be ready and then NASA can decide to bypass the
| bullshit.
| mlindner wrote:
| The gateway is where international partners are currently
| hooked in. If NASA is to cancel the Gateway without
| absolutely destroying it's relationship with international
| partners, it would need a replacement mission (say Moon
| surface modules) to make up for it.
| skissane wrote:
| > The current official plan is for Starship to take
| astronauts from the Gateway to the surface of the moon and
| back.
|
| Even before announcing the choice of Starship for HLS, NASA
| was already talking about bypassing Gateway for the first
| crewed lunar landing (Artemis III) and only visiting it on
| later missions - https://spacenews.com/nasa-takes-gateway-
| off-the-critical-pa...
|
| They haven't completely decided yet though. They don't know
| when the bits will be ready. If come time for the first
| crewed landing, SLS+Orion and Starship are ready but Gateway
| isn't, they'll just do the landing without Gateway. On the
| other hand, if Gateway is already ready by then, they might
| consider using it. One advantage Gateway has, is it gives the
| two astronauts who stay-behind on Orion a bit more room. It
| would also give them something to do - testing out Gateway
| systems.
| dillondoyle wrote:
| I can't believe that I'm understanding this correctly? Just
| to be sure: NASA's plan is to fly the insanely expensive
| hasn't even launched into space yet SLS, onto some non-
| existing docking station, then SpaceX fly to the moon. Repeat
| back (does Starship have to dock again why can't it just go
| straight back into earth)?
|
| While Starship can go to from earth to moon with a refueling
| stop alone? Even if sticking to the space dock why not the
| WAYYYY cheaper Dragon which just worked today (using a
| recycled rocket)?
| lutorm wrote:
| _hasn 't even launched into space yet SLS_
|
| I'm no fan of SLS, but check your terminology here: You're
| talking about Starship in the present tense, but it hasn't
| launched _either_, so you can't say it "can" go to the moon
| etc either.
|
| Starship is awesome, but it's an insanely ambitious
| project. No one knows how long it'll take to get it right.
| avmich wrote:
| Raptor engines are, yes, cutting edge. Serious stuff.
|
| Starship itself?.. Being built with such technologies, so
| cheap (Elon mentioned that Boca Chica works are quite
| small percents of what SpaceX is doing in terms of
| money), so fast - and yet we already have a successful-
| ish landing from ~10 km height.
|
| Of course, we don't know for sure. But it surely doesn't
| seem too bad, especially now - and for some it was clear
| when SpaceX was just created.
| m4rtink wrote:
| Well, Starship has definitely reached bigger height than
| SLS so far (unless you count some of the reused Shuttle
| engines). ;-)
|
| Also considering the planned SLS "landing" mode they are
| also on par so far.
| syoc wrote:
| I am way out of my comfort zone discussing this, but I
| really like the idea of building oribiting infrastructure.
| Not sure why they are not using an earth-moon Lagrange
| point. I agree that it would probably be cheaper and more
| practical to go directly to the moon with a simpler
| refuling scheme. I do however also believe that some
| infrastructure is needed for further space travel and a
| larger more permanent off-earth presence.
|
| Starting new missions from outside a strong gravity field
| seems like such a huge advantage. I guess most people want
| a destination and not just a more long term established
| presence.
| Yizahi wrote:
| Only some orbits would intersect with L1 point, others
| will require immense fuel waste to get there and then
| change orbit to original target. Also there are no gas
| stations in space, for multiple reasons - there is no
| steady demand to fuel in space, it is at best sporadic
| and spiky, and in the mean time you'll need to keep up
| cryo fuel from boiling off; then it is hard to operate
| anything remotely, so Gateway gas station would be harder
| to operate than ISS in LEO; there is no need to place gas
| station farther than LEO because in space we don't need
| to bother with actual distances, but with gravity. Earth
| to Mars is 62 million kilometers, so speaking in
| analogies it would make sense to refuel at half of the
| distance, similar to the traveling by car from New York
| to San Francisco. But in reality it is not. Getting 300
| kilometers from Earth to LEO takes 9 km/s of delta V,
| getting the rest 62000000 kilometers from LEO to Mars
| takes 5-6 km/s of delta V. LEO is much more than half way
| to Mars already and there is literally zero point is
| refuelling anywhere else (excluding fuel generation in
| space possibility).
| Armisael16 wrote:
| > Starting new missions from outside a strong gravity
| field seems like such a huge advantage.
|
| You don't get to do this, period. All your crew and all
| your materials are ultimately coming from Earth (or, in
| some plans, are mined in-situ). You use considerably more
| resources getting to your waypoint than you save by
| leaving from there.
|
| Being farther out of the gravity well isn't entirely
| positive either; you're losing out on significant savings
| from the Oberth effect. Earth-Moon Lagrange points are
| well past the minimum-cost orbit.
| avmich wrote:
| > All your crew and all your materials are ultimately
| coming from Earth
|
| Wait till we start making LOX (and later, I think,
| metals) on the Moon from regolith. The process is old and
| tested on Earth, the missing part is actually
| experimenting with this on the Moon. And as soon as we
| have more or less robust Earth-Moon transportation, this
| will become important, as it will significantly simplify
| near Moon operations.
|
| Do you know NASA runs, right now, competitions for e.g.
| lunar ice extraction and purifying?
| ethbr0 wrote:
| > _All your crew and all your materials are ultimately
| coming from Earth_
|
| This is the key state differentiator.
|
| If you bring everything from Earth, it doesn't make
| sense. (So why are we doing it now?)
|
| But once you start procuring resources from outside
| gravity well, things look different.
| jandrese wrote:
| It makes sense if you want to use the rockets you already
| have instead of building the absolutely titanic rockets
| you would need to carry everything in one trip. There are
| metallurgical limits to just how big you can make the
| rockets as well.
|
| But this isn't necessarily advocating for a full time in-
| orbit refuelling station either. The plan might be to
| instead launch 2 or 3 rockets, 1 with the stuff and the
| others with fuel. They meet up in orbit and the fuel
| rockets refill the stuff rocket so it can go on to Mars
| or wherever, then they return to Earth for the next
| mission.
| Yizahi wrote:
| Exactly what do you plan to acquire/create outside of
| Earth, and from where to where do you plan to transfer it
| realistically? Except for fully autonomous human colonies
| which will mine stuff nearby and use, almost no transfer
| of resources in space makes sense, it is way too costly
| and there is no demand (even imaginary). Since there is
| no need for that, there is also no need for transfer
| stations (warehouses) anywhere, be it a planet orbit or
| Lagrange points.
| m4rtink wrote:
| Propelant depots, those make all the difference.
| zardo wrote:
| They make sense for an individual mission. Bring up fuel
| and leave it in the parking orbit. But the optimal
| parking orbits are going to be different for different
| destinations, vehicles, and times.
| sneak wrote:
| I imagine that we'd need hundreds or thousands of people
| in space to make such a base/fuel depot worth it - IIRC
| it's less fuel to use a transfer orbit than to go to L4
| or L1 and stop on the way.
|
| Such a thing might make sense once there are, say, 50 or
| 100 starships.
|
| For the foreseeable future, all missions will "start" in
| Earth's gravity well due to the fact that the o2 and ch4
| are all down here. It will be some years until we have
| significant fuel stores in space.
| avmich wrote:
| > does Starship have to dock again why can't it just go
| straight back into earth
|
| Because Moon-bound Starship will be quite different from
| Earth-bound - not enough to not call it Starship, but still
| - the Moon-bound will be optimized for less gravity
| (different legs?), no atmosphere (no wings), braking using
| engines in the middle of the body, not in the tail section,
| Moon-specific systems like ladder or elevator etc.
| m4rtink wrote:
| AFAIK lunar Starship still has Raptors in the tail that
| do most of the burns, the "belt" engines are only used
| for the final landing phase to reduce the ammount of
| regolith kicked up by the rocket plumes contact with the
| surface.
| kimundi wrote:
| Separating the "get to/from moon" vehicle from the "land
| on/start from moon) vehicle has indeed been the plan for
| many years now.
| jandrese wrote:
| I don't think the Lunar gateway is so useful for people going
| to/from the moon, but for future trips to Mars and back.
| Having a place to stop and refuel would greatly reduce the
| size of rocket you need to launch from Earth.
|
| The choice of having it in Earth orbit vs. Lunar orbit comes
| with some tradeoffs. It may make more sense to leave it in
| Earth orbit, but ultimately having it at all substantially
| changes the calculus on a Mars trip.
| avhon1 wrote:
| Unless the fuel is being produced on the Moon, it would be
| more efficient for Mars-bound spaceships to fuel up in LEO.
| All Earth-departing mass has to pass through LEO, so it's
| simpler to rendezvous there rather than enter, and then
| leave, Lunar orbit.
|
| If launches are cheap, then refueling in LEO makes a lot of
| sense. Historically, this has not been the case at all, but
| it's all part of SpaceX's model for Starship.
| inglor_cz wrote:
| Lunar gravity is actually weak enough to make a space
| elevator from conventional materials possible. Even Kevlar
| would suffice.
|
| If fuel for interplanetary missions is produced on the
| Moon, a space elevator would make a huge sense for
| refueling of the ships.
| jandrese wrote:
| Doesn't the moon rotate too slowly to make a space
| elevator work? IIRC you can't take up a ground-stationary
| orbit around the Moon because the Earth would constantly
| knock your satellite around with its big gravity well.
| inglor_cz wrote:
| I think this is where the Lagrange points L1 and L2 would
| help.
| zardo wrote:
| You can have a ground stationary satellite if you tether
| it to the moon. Though obviously the tether has to deal
| with that extra load.
|
| The best sites for permanent outposts are the poles
| though, it would be quite a drive from the equator.
| rblatz wrote:
| That was my take on this too. NASA is buying themselves a
| backup plan for further SLS delays.
| DennisP wrote:
| I thought that was crazy at first but the Orion capsule uses
| proven reentry tech. SpaceX hasn't landed Starship
| successfully yet and hasn't proven their reentry strategy,
| and coming back from the moon will be harder because they'll
| be coming in faster. I can't blame NASA for not committing
| their astronauts to it yet.
|
| But yeah, I think SpaceX will prove it all works and then
| NASA has the option to change the plan. In the meantime,
| officially keeping SLS keeps Congress happy.
| mlindner wrote:
| The Lunar Starship requires a functioning Starship capable
| of reentering in order to refuel the Lunar Starship before
| it heads to the moon (and it will need to eventually travel
| back to the Earth for refueling after some number of uses).
| m4rtink wrote:
| I don't think the lunar Starship is ever intended for
| returning to the Earth after it's launched - it has no
| flaps and no heat shield.
|
| It will either be discarded after use or refueled and
| reused fully in space.
| avhon1 wrote:
| Lunar Starship won't be (intentionally, excepting
| emergencies or retirement) returning to Earth's Surface,
| but the plan might involve it returning closer to Earth
| for refueling.
| wmf wrote:
| Starship can come back from the moon to LEO then the crew
| transfers into a Crew Dragon and lands.
| cwkoss wrote:
| Yeah, once you have a large ship out of earths gravity
| well, would be a waste to land it back on earth. Heck,
| even if it breaks, park it in a stable orbit so the next
| generation can salvage it for parts as needed.
| m4rtink wrote:
| PSA: Most orbits around Moon are not long term stable due
| to underground mass concentrations.
| cwkoss wrote:
| Neat! If you park a satellite at moon geosychronous orbit
| how unstable is it? Would it be lost in the order of
| months or decades?
|
| Does that also effect the Lagrange points for the moon?
| Do human currently have anything parked at earth moon
| lagrange points?
| jccooper wrote:
| It would need lunar or high elliptic refueling to do
| that. Which is possible, but more complicated.
| [deleted]
| simonh wrote:
| The Lunar Starship has enough dV to land on the moon and
| return to orbit, about 3.44 km/s but boosting from the
| moon to Earth and braking into Low Earth Orbit actually
| takes more dV than that, about 3.94 km/s. Unless they
| build in extra 0.5 km/s capacity or about an extra 20%,
| it flat out won't be able to do it.
| wmf wrote:
| Here's where I got the idea and some different
| calculations:
| https://caseyhandmer.wordpress.com/2021/03/26/lunar-
| starship...
| simonh wrote:
| The diagrams say "Crew transfer in LEO or direct entry of
| Starship" as if they're interchangeable options, but
| these are not equivalent. Returning from the Moon and
| braking into LEO takes just as much dV as transferring
| from LEO up to Lunar orbit. Per the diagram that's 3.94
| km/s as I said.
|
| Conversely landing on the moon and returning to Lunar
| orbit takes 1.72 km/s twice, which is again consistent
| with my numbers if we assume the payload mass is
| constant. That may not be the case of course but any
| cargo taken from the Lunar surface to Lunar orbit will
| also need to be brought back to Earth somehow.
| ArPDent wrote:
| currently the lunar version of Starship is not designed to
| land back on earth - it lacks both the TPS and aero
| surfaces required for entry & landing.
| [deleted]
| whatiknow2 wrote:
| Sounds a lot like Gateway is Kubernetes the space version..
| medium_burrito wrote:
| Basically, yes.
|
| Gateway is smaller, doesn't have two airlocks, etc. If you want
| to build a station in LLO, just build it from a few starship
| hulls.
|
| Also, the stupid polar orbit around the moon isn't necessary if
| you have moon starlink (no comm loss on dark side). This saves
| energy otherwise needed for inclination changes.
| actinium226 wrote:
| > Also, the stupid polar orbit around the moon isn't
| necessary if you have moon starlink (no comm loss on dark
| side). This saves energy otherwise needed for inclination
| changes.
|
| What? Gateway is planned to be in a Halo orbit at L1. Getting
| to the lunar poles is actually cheaper from L1 than directly
| getting there Apollo style, and the poles are of interest for
| exploration due to areas of permanent sunlight (for power)
| and permanent shade (for potential ice).
|
| Moon starlink? For comms you just need one or two satellites
| at L2. The Chinese already have one there. And it's not the
| dark side, it's the far side.
|
| Goram people being wrong on the internet making me correct
| them grumble grumble.
| Armisael16 wrote:
| > What? Gateway is planned to be in a Halo orbit at L1.
|
| Can you provide a source for this? I'm not seeing anything
| that says gateway is ever expected to even get particularly
| close to L1.
| T-A wrote:
| > Gateway is planned to be in a Halo orbit at L1
|
| https://en.wikipedia.org/wiki/Lunar_Gateway#Orbit_and_opera
| t...
| valuearb wrote:
| Getting to the lunar poles from Earth through Gateway is a
| diversion that takes more energy than going direct.
| zardo wrote:
| No, it doesn't really change anything about the gateway plan.
| It was always unnecessary technically, and necessary
| politically (to support a lunar landing mission).
| unchocked wrote:
| The lunar tollbooth? Hope so.
|
| https://spacenews.com/op-ed-lunar-gateway-or-moon-direct/
| 7e wrote:
| It's not so bold; they're going with the lowest bidder.
| njarboe wrote:
| NASA's "bold bet" is also an insurance policy on the fact that
| SpaceX might have just built this Moon landing Starship version
| on its own and get back to the moon first. Especially if it got a
| large private backer, like Yusaku Maezawa is backing the dearMoon
| project. NASA's relevancy would definitely take a hit if that
| happened, so funding it themselves is a good idea. I don't see
| the other two bids getting private funding to go forward without
| NASA support.
| yummypaint wrote:
| Going to the moon is not a good value proposition as far as
| science per dollar. SpaceX and other players only care about
| supporting science to the extent it makes them money. In my
| opinion NASA never had the budget for a moon mission anyway.
| Scrapping space telescopes and other far more useful
| instruments to pull a publicity stunt would be irresponsible.
| NASA is still the only party willing to support the less
| glamorous but more important work. This division of labor is
| good. Companies can do things that make good marketing material
| and NASA can continue managing the science that motivates the
| entire excercise in the first place.
| api wrote:
| It's not about science. Just like the ISS it's about
| engineering. It's about developing space infrastructure to
| enable both future science and future space
| migration/exploration.
| amelius wrote:
| > Scrapping space telescopes and other far more useful
| instruments
|
| A moon telescope is actually a very promising idea.
|
| https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_.
| ..
| spfzero wrote:
| I think if SpaceX only cared about things to the extent it
| makes them money, they would have picked a simpler business
| and made a lot more money by now.
|
| I agree with you about science-per-dollar, but I don't think
| that was ever the criteria for large projects like this (or
| ISS). Sometimes the payoff is in learning to do the next hard
| thing, building the next generation of tools, etc.
| misterkrabs wrote:
| I think if there's money to be made, there's a business
| that will pop up to fill that niche.
| adt2bt wrote:
| > SpaceX and other players only care about supporting science
| to the extent it makes them money.
|
| In some ways true, but it's hard for me to accept they're a
| cold, calculating money-grubber despite the common refrain
| that corporations only exist to make money. SpaceX will gain
| an absolute massive amount of public goodwill by bringing
| humans back to another celestial body after 50+ years. That
| goodwill pays off over the long term in money terms.
| skissane wrote:
| A corporation exists to do whatever its owners wish to do
| with it. It is only true that "corporations only exist to
| make money" when that's the sole or primary wish of their
| owners. Musk owns over 50% of SpaceX equity (and over 70%
| of voting rights), and it is pretty clear his primary
| motivation is not simply "make as much money as possible".
| On the contrary, I think his primary motivation with SpaceX
| is to try to make the science fiction stories he read as a
| kid come (partially) true, and to try to leave his mark on
| human history. Making money is just a means to that end,
| not the end-in-itself.
|
| (The remainder of SpaceX is owned by investment funds,
| Google, etc, whose motivation is much closer to just "make
| money".)
| bpodgursky wrote:
| The goal of NASA, or spaceflight at all, has never been to
| maximize science per dollar. That is a new invented
| benchmark.
|
| The goal was, and IMO still is, to put ourselves in space.
| Diederich wrote:
| Science/$ is something of a "new invented benchmark", but I
| think it's useful to a point.
|
| I fully agree that "put ourselves in space" was the prime
| driver for NASA up through Apollo, and has certainly played
| a role since, but NASA as a driver of scientific discovery
| has become, I think, the main NASA thing.
| mlindner wrote:
| "Science" isn't even a fungible unit, so you can't even
| say "science/$". Even a specific type of science, say
| "Earth Science", isn't even a fungible unit. So it
| doesn't make much sense to talk about "Science/$".
| [deleted]
| yummypaint wrote:
| This can be true when trying to compare science A against
| science B. However, there is no controversy when
| comparing a program designed to deliver an instrument
| package with one designed to build a brand.
|
| Also, there are frameworks for evaluating science output
| per dollar. This is what funding agencies do when
| creating and managing grants. There is alot of
| subjectivity involved which is why DOE program managers,
| for example, are pulled from practicing experts in the
| relevant field and tend not to serve very long in those
| positions before circulating back.
| mulmen wrote:
| NASA evolved from NACA, they have always been an
| aeronautical research group with a focus on practical
| application. They do way more than just (manned)
| (space)flight.
| pfdietz wrote:
| That depends on how much it costs to go to the Moon.
| [deleted]
| eloff wrote:
| Imagine in an alternate universe where they decided to back an
| SLS type program over SpaceX, perhaps due to corruption of some
| sort.
|
| In that case, there's probably better than 10-1 odds that
| SpaceX would have beat them there for a fraction of the price.
| They would have looked stupid and been the laughing stock of
| the country. Future budgets would have been seriously cut.
|
| They made the smart decision here to back SpaceX. Love or hate
| Elon Musk, his companies get results in an incredible fashion.
| So far everyone betting against them has got horribly burned.
| They are excellent examples of American ingenuity and
| enterprise.
| inglor_cz wrote:
| Well, this guy finally considers himself too old to run for
| re-election again:
|
| https://en.wikipedia.org/wiki/Richard_Shelby
|
| SLS had a big fan in him, and he used to punch above his
| weight in space matters.
| merpnderp wrote:
| They already look stupid for being part of SLS and having
| prominent admins say things like landing a rocket isn't that
| hard and NASA could have done it in the 80's if they'd wanted
| to, or the Space Shuttle which was a massive downgrade from
| the Saturn series.
| [deleted]
| toomuchredbull wrote:
| I hope as a test Musk launches a cyber truck to the moon and
| drives around. The ultimate flex.
| unchocked wrote:
| I suspect they will. Cybertruck's chassis and battery capacity
| will dominate every other lunar rover architecture, and a ton
| of NRE has already been spent making it a production vehicle.
| Lunarizing the platform will be cheap, and Starship has ample
| payload mass margins.
| walrus01 wrote:
| > All of this has led to criticisms that SLS is a jobs program.
| Indeed, it provides jobs in all 50 states and supports hundreds
| of small businesses
|
| They don't call it the "Senate Launch System" for no reason...
| ncmncm wrote:
| Last I read, it was in only 48 states. Strictly speaking they
| needed only 26. It will be very hard to kill SLS even with
| SpaceX able to provide launch capacity at <0.3% of the price.
|
| Betting here they will actually launch one SLS, or even two,
| but not crewed.
| mattkevan wrote:
| Dunno why it's called the Senate Launch System when Senate
| Lunch System is right there.
| sschueller wrote:
| To me this seems extremely risky. There are so many things that
| still need to be solved on Starship such as in LEO refueling.
|
| I hope NASA knows what they are doing.
| spaetzleesser wrote:
| I hope they will go back to pushing the limits more again.
| Since the Space Shuttle and now the SLS they got stuck in a rut
| and iterated very slowly. It's unbelievable how long the SLS,
| which basically repeats what has been done 50 years ago, is
| taking and how much it costs. Better put that money into
| several programs that have a chance of failing but will also
| deliver new technology.
| unchocked wrote:
| Yup. Break the tyranny of mission assurance.
| spfzero wrote:
| Much more need to be solved for the other two options, so the
| choice seems logical. Whether the best option is a good enough
| option, is a different question.
| 2OEH8eoCRo0 wrote:
| I had it the other way around. I was worried about SpaceX
| overselling their actual capabilities until NASA gave them the
| contract.
| bryanlarsen wrote:
| Dynetics also required refueling and the National Team required
| assembly in NHRO. SpaceX was seen as less risky than the other
| two because their refueling was in low Earth orbit and was done
| prior to human launch.
| mlindner wrote:
| NASA rated SpaceX's approach equal or better in technical areas
| and management areas than the competitors, and it was the
| cheapest.
| themgt wrote:
| Worth noting orbital refueling _may_ not actually be that
| difficult, it was strongly rumored that Senate Launch System
| backers put the kibosh on refueling because it would jeopardize
| the SLS jobs program if it worked:
|
| _" We had released a series of papers showing how a
| depot/refueling architecture would enable a human exploration
| program using existing (at the time) commercial rockets,"
| Sowers tweeted on Wednesday. "Boeing became furious and tried
| to get me fired. Kudos to my CEO for protecting me. But we were
| banned from even saying the 'd' word out loud. Sad part is that
| ULA did a lot of pathfinding work in that area and could have
| owned the refueling/depot market, enriching Boeing (and
| Lockheed) in the process. But it was shut down because it
| threatened SLS."_
|
| https://arstechnica.com/science/2019/08/rocket-scientist-say...
| thaeli wrote:
| It _is_ very risky, but the source selection statement lays out
| in great detail how both other bids were much worse.
| toomuchtodo wrote:
| SpaceX needs to solve this to go to Mars, NASA is simply paying
| them to learn (similar to how full fare launches allowed them
| to learn to reuse the first stage and keep it for themselves).
| HPsquared wrote:
| I don't want to sound too cavalier, but launching and landing
| are objectively hard - need a combination of power and finesse.
| Isn't refuelling just connecting a pipe and an ullage motor?
| the-dude wrote:
| For example, the internet is just a bunch of pipes. How hard
| can it be?
| HPsquared wrote:
| The propellant depot is just a big truck, not a series of
| tubes.
| ceejayoz wrote:
| https://en.wikipedia.org/wiki/Propellant_depot#Engineering_d.
| .. has a pretty good list of concerns.
| JulianMorrison wrote:
| Starship's idea of (1) you send the fuel up in another
| Starship and (2) you refuel by bumping uglies and then
| accelerating in a direction that makes the fuel simply fall
| into the empty vehicle, together solves a lot of problems
| that imply a static depot.
| bpodgursky wrote:
| There would be many other core unsolved technical challenges if
| they had gone with a traditional system like the SLS. For
| example:
|
| - Standing it upright
|
| - Fueling it
|
| - Launching
|
| - Building it
|
| End of the day, Starship is a new and not-fully-proven design,
| but (parts of it) _have_ launched, and NASA knows that SpaceX
| is committed to the vision either way. Much better than a
| contractor design which exists only on paper and only to win a
| bid.
| avmich wrote:
| Orbital refueling is done for decades; e.g. Progresses supplied
| Soviet space stations with fuel to maintain the orbit.
|
| What's trickier is orbital refueling of cryogenic liquids -
| LOX, liquid methane. It still looks easier than refueling with
| LH2, and ULA did a lot of work with that (search for
| "propellant depot"). Active cooling might be required; humanity
| had experience storing cryogenics in space for long time (e.g.
| Buran, which used LOX for RCS, was able to store it for a month
| on orbit), but we still might want a better solution (the one
| which actively turns vapors back into the liquid phase using
| onboard energy and radiators).
|
| Yet there is little which seems too complex in the refueling
| idea.
| m4rtink wrote:
| IIRC ULA had a plan to run an internal combustion engine off
| the hydrogen/oxygen boil off, providing power for stage
| systems and or cooling/recondenser in their ACCESS upper
| stage concept.
|
| Of course ideally you don't want to loose any propelants to
| boil off but it still seems like a nice idea.
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