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Arthur T Knackerbracket has found the following story:
A total of 14 companies have now entered the race to develop landers to deliver goodies to the Moon as NASA plans to send the first woman and the next man to our nearest rocky companion by 2024.
Five vendors joined the growing list on Monday, according to a media teleconference broadcast on NASA Live.
Some of the most recognizable names include Blue Origin and SpaceX, founded by tech billionaires Jeff Bezos and Elon Musk. Other lesser known corps include Ceres Robotics, geared towards AI and space robots, Tyvak Nano-Satellite Systems, focused on building tiny satellites and CubeSat products, both based in California, and the Sierra Nevada Corporation, an aerospace biz based in Nevada.
NASA regularly searches for companies to partner with for its spaceflights. None are more prestigious than crewed missions. The Commercial Lunar Payload Services (CLPS) initiative was set up for candidates to win prized contracts to help NASA with its goal of launching the first woman and man onto the Moon as part of its Artemis program.
“The CLPS initiative was designed to leverage the expertise and innovation of private industry to get to the Moon quickly,” said Thomas Zurbuchen, associate administrator of the Science Mission Directorate at NASA. “As we build a steady cadence of deliveries, we’ll expand our ability to do new science on the lunar surface, develop new technologies, and support human exploration objectives.”
“Buying rides to the Moon to conduct science investigations and test new technology systems, instead of owning the delivery systems, enables NASA to do much more, sooner and for less cost, while being one of many customers on our commercial partners’ landers,” Steve Clarke, deputy associate administrator for exploration in NASA’s Science Mission Directorate, added.
[...] The CLPS contracts have a total combined value of a $2.6bn. The 14 companies in the pool will be allowed to bid for contracts, and NASA will award them based on technical capabilities, price, and schedule.
Also covered at Ars Technica: One part of NASA seems serious about fostering aerospace innovation and Space News.
(Score: 2, Informative) by Anonymous Coward on Wednesday November 20 2019, @08:59AM (14 children)
Refueling in orbit is no more difficult than docking with the ISS. Exact same mechanics in play.
NASA had plans for a streamlined in orbit refueling system as far back as the 70s, and it was completely viable. Reason we never got there wasn't technical, it was political.
Really looking forward to the future since it's never looked brighter, but it's also kind of disappointing to imagine where we could have been if not for idiotic politics. Fortunately it's looking like space of the future will be driven by companies and not governments, , so I think there's very good reason to believe the future we're looking towards today is not like the future those in the 70s thought they were looking towards.
(Score: 2) by Immerman on Wednesday November 20 2019, @03:19PM (11 children)
Hopefully not much worse, but not quite *exactly* the same mechanics. Refueling adds the connecting of the cryogenic CH4 and O2 propellant tanks, then actively accelerating the linked ships in order to transfer hundreds of tons of propellant. A little more involved, and at a much larger scale. And scale matters - for starters it dramatically increases the residual forces involved at the moment of contact. Ideally you're propulsion system will bring you to a complete relative stop at the moment of contact - but that never happens.
(Score: 0) by Anonymous Coward on Wednesday November 20 2019, @04:45PM (6 children)
If I'm not misunderstanding you, you're implying they're planning to accelerate to get the fuel flowing? Why? I'd just assumed something simple and straight forward like a 'kinetic pump' (something like a giant syringe) would be more than enough?
(Score: 0) by Anonymous Coward on Wednesday November 20 2019, @08:01PM (2 children)
And how hard is it to pull a vacuum when you are in orbit?
(Score: 0) by Anonymous Coward on Wednesday November 20 2019, @10:36PM
Opening a valve.
(Score: 2) by Immerman on Thursday November 21 2019, @04:27PM
Easy, but what does it buy you? You're not trying to vent fuel into space, you're trying to move it from a mostly-empty tanker (89% of its fuel was required to get the last 11% into orbit), into a partially-full Starship. And the Starship's tanks have to remain at the same high pressure as the Tanker's, or the fuel will just boil away.
(Score: 2) by takyon on Wednesday November 20 2019, @10:27PM
https://www.engadget.com/2019/09/28/starship-refueling-spacex/ [engadget.com]
Some more discussion here: https://forum.nasaspaceflight.com/index.php?topic=48771.105 [nasaspaceflight.com] and I'm sure you can find a lot more in that thread.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by Immerman on Thursday November 21 2019, @02:36AM
Why? Presumably because in theory it's easier that way - all you need is to connect a length of pipe between the two tanks (which you'll need regardless), open the valves, and slowly accelerate towards the tanker using the maneuvering rockets you already have, and all the propellant naturally settles out of it into the ship being refueled. You don't actually need a pump to generate pressure, since the two tanks are already going to be at the same pressure anyway - the vapor pressure of methane at the ambient temperature.
In fact, if you used any other process you'd probably have to accelerate anyway, just to get the fuel to settle onto the pump or whatever instead of sloshing around at the far end of the tank in freefall. So really, anything else you do is just adding complexity.
(Score: 2) by Immerman on Thursday November 21 2019, @02:45AM
Oh, and there's all sorts of stuff inside the methane tank (namely, the oxygen tank, and two "mini-tanks" to reliably get the engines burning during re-entry, when the main tanks are down to the sloshing dregs.) which interferes with a syringe process. A cutaway: https://www.humanmars.net/2019/08/cutaway-diagram-of-spacex-starship.html [humanmars.net]
Even without that, you'd also have to compress the original two-tank volume down to a one-tank volume, which means doubling the pressure (or going very slowly).
(Score: 2) by Muad'Dave on Thursday November 21 2019, @01:56PM (1 child)
Why pump? Jettison the old tank and dock with the (identical) new tank.
(Score: 2) by Immerman on Thursday November 21 2019, @02:44PM
Because basically Starship is a fuel tank with some engines on one end, and a small cargo chamber at the other - essentially the tank *is* the spacecraft by, so you haven't gained much, and you've made your rocket considerably heavier and more expensive to be able swap out the tank.
Plus, you need a lot more fuel than that.
According to the plan, a fully fueled Starship will contain around 1,200,000kg of propellant, and can lift a payload of 150,000kg into low orbit, at which point its tanks will be close to empty. So, if you want to fully refuel in low orbit it's going to take eight launches to carry enough fresh fuel into orbit as payload. More if you're refueling in a high orbit, such as is the plan for a moon landing, Mars launch, or pretty much any other mission you'd need to refuel for. And you're going to want to move all those launches worth of fuel into a single tank before you depart.
(Score: 0) by Anonymous Coward on Thursday November 21 2019, @03:17PM (1 child)
Why would you have to do that? I hear that heating stuff to make it go from liquid to gas generates some pressure. If the tanks are both full there's no need to transfer any fuel. If one of the tanks is empty then it shouldn't be too hard to make stuff in full tank go into the empty tank when connected, especially in free-fall.
(Score: 2) by Immerman on Thursday November 21 2019, @04:21PM
Well, a quick breakdown of relevant points:
- The tanker's tank will be mostly empty when it reaches orbit. It takes 1,200,000kg of fuel to lift the 150,000kg of payload (more fuel) into orbit, so the tanker's tank will only be around 1/9th full when it starts transferring fuel to the other ship.
- Assuming you want to fully refuel the Starship, you're going to need at least eight refueling maneuvers of 150,000kg of fuel each - and after the first one the Starship will actually be carrying more fuel than the tanker.
- As long as there's even one drop of liquid fuel in each tank, both tanks will always be at roughly the same pressure, regardless of how full or empty they are: the vapor pressure of methane (or oxygen, depending) at the ambient temperature. Anything below that pressure and fuel will evaporate to increase the pressure, while anything above that pressure will cause fuel to condense (both are actually constantly happening, but the pressure causes a net phase transition in one direction or the other). You could heat the tanker to generate a pressure gradient, but the next issue presents some major problems.
- Without acceleration you're in freefall. And if your tanker has burned off 89% of its fuel getting there, the tanks will be filled mostly with vapor, and only 11% liquid - which means you've got a bunch of propellant droplets floating around at random inside the tank (well, probably mostly one big one as they merge). Just connect the tanks and increase the pressure in the tanker, and it'll mostly be vapor being transferred - you need to figure out how to transfer the liquid.
That last one is a big problem - transferring vapors is pointless, there's not enough mass there to do much good. You need to transfer the liquid, where almost all the mass is. So, what are your options?
1) You could have a robot hose in the tank chasing down the floating droplets.
2) You could put some sort of membrane in the tank and pressurize the space between the membrane and the tank wall to force everything out - but that means doubling the pressure as you force two tanks worth of fuel into one tank, and that membrane needs to operate repeatedly at cryogenic temperatures without cracking, and not get crumpled or otherwise stressed when the tank is being filled on Earth. Plus, the methane tank has several other tanks inside it*, which complicates things considerably
3) You could accelerate slightly, so that all the fuel settles down to the "bottom" of the tank where it's supposed to be, and your pumps or whatever can move it around.
(3) is the simplest option, requiring the least extra hardware (which all eats into payload capacity). And, once you're doing that, then you don't actually need pumps or anything else to transfer the fuel. Provided you put the the tank being refilled "below" the tanker, the liquid fuel will settle right out of the tanker and into the ship being refueled.
*the methane tank contains the oxygen tank(sort of - they have a shared hemi-spherical wall), and two smaller "reentry tanks" that are used during reentry when the fuel in the almost empty main tanks is sloshing around every which way, and wouldn't reliably reach the engines
(Score: 2, Informative) by Anonymous Coward on Wednesday November 20 2019, @04:31PM (1 child)
WAY further back than the 70's. It was a major mission design decision in the early 60's. Von Braun wanted to do a rendezvous mission for assembly/fueling before going to the moon, but the program decided to do it in one shot with a really big rocket.
Here is a paper [si.edu] that goes in detail. The paper abstract (in case you can't access it):
(Score: 0) by Anonymous Coward on Wednesday November 20 2019, @04:47PM
That is an awesome read. Thanks!