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Launch a Water-Propelled Satellite into Deep Space

kickstarter.com

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Re: Launch a Water-Propelled Satellite into Deep Space

#31

Post by dnautics »

ars wrote: post #22
Gravityloss wrote: post #2

They sure write a lot but for someone more technologically oriented, the water plasma engine or CAT is most interesting. http://pepl.engin.umich.edu/thrusters/CAT.html "First, from a propellant tank, our fuel propellant will be injected from its storage tank into the plasma liner, a quartz chamber that distributes the gas and contains the plasma. The gas is turned into a plasma by a radio frequency antenna that surro…

So basically the water is reaction mass, and it's actually powered by solar cells? They should write that WAY more prominently on the kickstarter page, as is it feels like a scam.

I felt that way a little bit, but since I already knew the physics (and heard of a similar system that uses a microprinted array of spikes (conductive spikes naturally create a charge separation when pumped to a voltage) I wasn't put off by it.

They're going to reach their goal, so it might be a moot point

Re: Launch a Water-Propelled Satellite into Deep Space

#32

Post by j-g-faustus »

jeremyjh wrote: post #25
ars wrote: post #22

Earlier quoted context omitted.

So basically the water is reaction mass, and it's actually powered by solar cells? They should write that WAY more prominently on the kickstarter page, as is it feels like a scam.

In the second sentence of the kickstarter page it says "a new rocket propulsion system powered by the Sun and propelled by water". I think that is pretty clear.

Clear for people in the know, I guess.

But suppose I had a Kickstarter for a car on the same premises: "A revolutionary car powered by sunlight and water - fill up with water every now and then, and it will run forever". No further details. Would you buy?

I think it's a very small percentage of the world that would know off the bat why "sun and water" could work for a spacecraft, but not for a car.

I think some more detail on the physics behind it, aimed slightly below say Physics 101 level, would help to convince more people to contribute. It makes it simpler to distinguish this from "crystals can change your life" or "lose X pounds of weight in Y days" style marketing, which promise the moon but don't explain how their miracle is supposed to work.

They do give an explanation in their link[0], but I think having a summarized version on the Kickstarter page itself would help donations. (To be clear, this is a comment on the marketing, not on the physics or feasability.)

[0] http://pepl.engin.umich.edu/thrusters/CAT.html

Re: Launch a Water-Propelled Satellite into Deep Space

#33

Post by gus_massa »

acjacobson wrote: post #29
outworlder wrote: post #24

I am unsure what is the relevance of water in this project. It is not like the noble gases used in other engines (including ion) are difficult to find or too expensive. Unless there's the long-term goal of collecting water in order to 'refuel' the craft. Which is unlikely, as they are too tiny to afford thee extra machinery. I'm thinking it's just a matter of reducing for the 'fuel tanks'.

While I am no expert in chemistry he mentioned that one of the benefits of using water was the fact that it is in a liquid state and thus you could effectively store more energy within a finite amount of space. At least one of the noble gases (argon) does not compress down to a liquefied state, so perhaps that applies to the others? Large compression tanks are also quite heavy, so perhaps that is a consideration too.

The page is not very clear. The energy comes from the solar cells. They are using the water to store mass, no energy. It’s (probably) easier to store a lot of mass of water as a liquid than a lot of mass of Xenon because you must compress it a lot.

The idea is that to accelerate in one direction, you must push something in the opposite direction. They will convert the water into plasma (imagine very hot ionized water vapor) and push it using the energy from the solar cells.

It’s different from a normal rocket, because in a normal rocket the energy and the mass come both from the fuel and oxidizer.

Re: Launch a Water-Propelled Satellite into Deep Space

#34

Post by maaku »

alanctgardner2 wrote: post #19

> CAT is currently at NASA Technology Readiness Level (TRL) 3, meaning we are in the midst of performing experiments to probe its feasibility, thanks to private sponsorship Clicking on the link, 3 is a really far way from actually flying. Like, they haven't successfully demonstrated this in a lab yet. For reference, there are 9 stages, the final one being "it's in space". It seems like an interesting idea, but I'm wi…

TRL 9 is "we have nothing more to learn about it."

"It's in space" would be TRL 6. I think this is the appropriate level at which to be running this kind of kickstarter.

Re: Launch a Water-Propelled Satellite into Deep Space

#35

Post by Wingman4l7 »

Taylorious wrote: post #18

Why only 50k? That's peanuts for researchers. U of M is one of the top universities in the US, they couldn't get a major grant for this? Could it be that the technology is not as promising/proven as they would like it to appear?

Well, they tried raising $200,000 back in July and only got to the ~$68,000 mark: http://www.kickstarter.com/projects/longmier/cat-a-thruster-...

In an update after they failed to reach their funding goal they stated:[1]

"[...] we attracted a lot of attention from a few government and commercial partners. Some of these groups intend to fund this research and we are looking into these options. We are also considering re-listing the kickstarter campaign with a few tweaks, a lower funding goal, and some revised rewards."

[1]: http://www.kickstarter.com/projects/longmier/cat-a-thruster-...

Re: Launch a Water-Propelled Satellite into Deep Space

#36

Post by Wingman4l7 »

noonespecial wrote: post #3

I'd just like to point out that their first kickstarter didn't make even half its goal. We all talk about how we wish more money was devoted to research like this. Skip your latte today and toss them a fiver.

True, but their original goal was 4x this amount.

Re: Launch a Water-Propelled Satellite into Deep Space

#38

Post by dnautics »

tocomment wrote: post #27

So wouldn't this build up a charge over time if its giving off electrons or am I misunderstanding?

usually for ion propulsion systems you throw off positive ions and also include a rear-facing electron gun. Don't know the exact details, but if it's throwing off neutral waters, with some proportion of charged waters, those charged waters will find their way back to satellite via coulomb forces, but the uncharged water propulsive component will still make a difference.

Re: Launch a Water-Propelled Satellite into Deep Space

#40

Post by tlarkworthy »

mcross wrote: post #39

Perhaps this is a dumb question, but wouldn't the water freeze?

low pressure lowers the boiling point. Water is space will spontaneously boil (i.e. its molecules will separate and drift apart in a vacuum, because there is no background material to hold them together anymore)
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