Water based propulsion for deep space efforts

[Carl White]

https://techcrunch.com/2018/07/21/prope ... r-liftoff/

First product has a specific impulse of 150 to 180, later products higher as the supplied power increases. The chief benefit seems to be cost.

EDIT: more information on the website of the company ("Momentus"):

http://momentus.space

[paperburn1]

I think they are looking at water being everywhere for fuel in the asteroides and luna. Earth orbit to cis-lunar space (the region between the Earth and the Moon, including a variety of locations such as Lagrange points, geostationary orbit, and more) The main advantages besides cheap fuel from everywhere is Real payload fractions with this system,you can haul more stuff, looks like all you need is an insulated water tank and the motor, none of the problems with cryogenic storage of propellant pumps and the need for a heavy duty rocket. The ISP of 180 is not that much lower than one proposed solution of using aluminum and oxygen for your ferry fuel, an ISP only a third higher. you should be able to get water from the moon just by baking the ore and no extensive processing required. cracking water into hydrogen and oxygen for the launch to lunar orbit would most likely be used to get to lunar orbit. But transfer would easy be acomplished with solar panels and this power plant.
Water from melted lunar ice could be used directly as a propellant. A steam rocket, with energy supplied by some external means such as a solar collector or nuclear reactor, would develop between 100 and 230 seconds of specific impulse (Isp) using the water directly as propellant.
This system is proposing similar numbers
****
USING LUNAR ICE
Anthony C. Zuppero, Bruce G. Schnitzler*, Thomas K. Larson
Idaho National Engineering And Environmental Laboratory (INEEL)
*****
The issue is whether to use the water directly, or to split and convert it into cryofuels. Landis5 and Zuppero6 examined this issue where propellant is abundant and the space transportation system is only limited by the total energy the system can give to the propellant. They showed that the optimum payload delivered per ton of launched hardware is greatest when the rocket exhaust velocity is about 2/3 the mission velocity. Since the mission velocity to escape the lunar gravity is about 2600 m/s, the optimum exhaust velocity is about 1730 m/s. This would imply a rocket specific impulse of about 175 seconds. A steam rocket with mixed mean outlet temperature of about 800 Kelvin would provide this performance.
http://neofuel.com/moonicerocket/


sorry about babbling but the idea has promise.

[hanelyp]

Performance using water as propellant is directly related to how you're heating the water. With solid core fission the ISP isn't so great, it's hard to deal with the hotter reactors and corrosive effect of water. With solar heated water you might get some very good ISP, at not so great thrust because of collector mirror size difficulties.

[ladajo]

The irony in all this is that space propulsion is easy. The real problem is we have no patience for moving about in terms of cosmic scales.

[Diogenes]

https://techcrunch.com/2018/07/21/prope ... r-liftoff/

First product has a specific impulse of 150 to 180, later products higher as the supplied power increases. The chief benefit seems to be cost.

EDIT: more information on the website of the company ("Momentus"):

http://momentus.space

Seems like I read a Heinlein story or two using water as reaction mass.

[paperburn1]

Destination Moon , the also made a movie about it
Water powered nuclear rocket

[Tom Ligon]

https://techcrunch.com/2018/07/21/prope ... r-liftoff/

First product has a specific impulse of 150 to 180, later products higher as the supplied power increases. The chief benefit seems to be cost.

EDIT: more information on the website of the company ("Momentus"):

http://momentus.space

What a waste of water! I can see an Isp that low for maneuvering thrusters, maybe.

Need I point out that the SSMEs used water as the primary reaction mass, and developed an Isp of 460 seconds. Well, yeah, they ran hydrogen rich. But electrolysis of water at the in-situ extraction site, via solar, nuclear, or what have you, should more than double the performance suggested above.

Many of RWB's designs used water as the reaction mass, and his worst performance was around 1200 seconds, for Cis-Lunar missions.

But I'll bet Larry Niven would get a kick out of it. Have any of you read The Integral Trees?

[krenshala]

The Integral Trees and The Smoke Ring were two of my first Niven books. Very nice, especially with the way the denizens moved around in the environment. Of course, Footfall holds a special place in my heart due to the use of a real Orion spacecraft (even if it does point out why we never went far with the design).

[Carl White]

The owner of the company replied to a comment attached to the article:

If the specific impulse is as they say, 150 to 180, then this is completely worthless technology. Chemical rockets get a specific impulse of up to 400, I think they meant either 1500 or 15,000. GET YOUR FACTS RIGHT PEOPLE

Hey CJ,

Zeal is a small thruster for an attitude control. It doesn’t have high ISP, because it shouldn’t, it should be small and with low power consumption. And Zeal is not plasma thruster, it is resistive electrothermal thruster, chamber temperature are limited with metal properties.

For larger systems, like Ardoride, or Fervoride we don’t have such limitations, because we are heating not with resistive element, but with plasma discharge, so ISP is to 1000 sec, 3 times higher then for chemical propulsion.

MK

So as Tom Ligon observed, the initial product isn't meant for propelling a spacecraft from A to B.

[paperburn1]

What a waste of water! I can see an Isp that low for maneuvering thrusters, maybe.

But I'll bet Larry Niven would get a kick out of it. Have any of you read The Integral Trees?

Yes in a higher gravity environment it really doesn't make any sense not to crack the water into hydrogen and oxygen. But in a low gravity environment like the moon or lower the advantages I think would be coming from the fact that you would need minimal infrastructure to launch from the surface of the moon or smaller planets/asteroids. Basically all you have to do is feed up a big can water to 1500°F and pull the cork out of the nozzle. The temperatures are within the range of being handled by the materials we have solar mirrors could achieve those temperatures, and the pressures from heating the water up so hot by my understanding about 3000/3500 psi are containable by alloys we currently manufacture. So I think there is a very useful opportunity for a moon base Alpha situation where you have to haul a large amount of infrastructure to set up and maintain vice some Mylar solar mirrors and maybe a few solar panels to run some resistive heaters.

I don't know – just kind of my bootstrap thoughts on it keeps his away from the nuclear problem of people freaking out about something that's actually nothing at least until we can develop a Polywell reactor. I really don't have any great hopes of the current administration funding such an endeavor but I guess we'll just wait and see.

[Tom Ligon]

The owner of the company replied to a comment attached to the article:

Hey CJ,

Zeal is a small thruster for an attitude control. It doesn’t have high ISP, because it shouldn’t, it should be small and with low power consumption. And Zeal is not plasma thruster, it is resistive electrothermal thruster, chamber temperature are limited with metal properties.

For larger systems, like Ardoride, or Fervoride we don’t have such limitations, because we are heating not with resistive element, but with plasma discharge, so ISP is to 1000 sec, 3 times higher then for chemical propulsion.

MK

Hah! In that case, they stole my idea. I've had electrically heated steam jets for attitude control on my Sunfire Ion Jet since ... dunno, then 1980's? Of course, steam propulsion is not exactly my idea. Hero of Alexandria probably gets the ultimate credit.

[alexjrgreen]

Hah! In that case, they stole my idea. I've had electrically heated steam jets for attitude control on my Sunfire Ion Jet since ... dunno, then 1980's?

Did you ever write the end of that story?

[Tom Ligon]

Did you ever write the end of that story?

The novel in which I first developed the craft has never been finished, but I've used the Sunfire in two published stories, "The Devil and the Deep Black Void", and "The Gardener."

As I said, I can't really claim the invention. There are a couple of thousand years of prior art. It'll work.

[KitemanSA]

Yes, I am reprising a VERY old thread, but…
Seems to me that O2 would be a better fuel. O2 is in EVERYTHING, water not so much. Indeed, we would use the H2 from water to get the O2 out of lots of things.
Just a thought!

[usesbiggerwords]

As I said, I can't really claim the invention. There are a couple of thousand years of prior art. It'll work.

What? You're telling me boiling water isn't new tech? Say it ain't so, Tom.

/sarc, obviously