

Launch a Water-Propelled Satellite into Deep Space - mrchucklepants
http://www.kickstarter.com/projects/longmier/cat-launch-a-water-propelled-satellite-into-deep-s

======
Gravityloss
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](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 surrounds the liner and launches a plasma wave known as a
"helicon." Then the plasma is launched out of the liner with magnetic fields
from extremely powerful permanent magnets, pushing the satellite in the
opposite direction. Unlike conventional rockets, almost any gas can be used as
propellant for the CAT - even water vapor! "

Some ion engines use electrostatics (charged grids) for accelerating the ions.
Maybe here it's just their random movement?

Here's the noble gas helicon double layer thruster, I don't know how related
the CAT is related to this:
[http://physics.anu.edu.au/prl/sp3/hdlt/how_does_it_work.php](http://physics.anu.edu.au/prl/sp3/hdlt/how_does_it_work.php)

~~~
ars
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.

~~~
jeremyjh
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.

~~~
j-g-faustus
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](http://pepl.engin.umich.edu/thrusters/CAT.html)

~~~
DrStalker
They could do a little comparison of existing technologies:

Chemical rockets - put fuel and oxidizer together, burn them, resulting gas is
shoved out the back and pushes the rocket forward.

NERVA - reaction mass is heated by a nuclear heat source, resulting gas is
shoved out the back and pushes the rocket forward.

Ion thruster: reaction mass (such as xenon) is charged electrically using a
grid and the resulting ions are shoved out the back and pushes the rocket
forward.

CAT: reaction mass (such as water) is charged electrically using a glass
bottle thingy and the resulting plasma is shoved out the back and pushes the
rocket forward.

Shove that in an infographic and you can get the basic concept across to
someone who knows high-school physics and sound convincing to people that
don't even have that level of background knowledge.

[http://en.wikipedia.org/wiki/NERVA](http://en.wikipedia.org/wiki/NERVA)
[http://en.wikipedia.org/wiki/Ion_thruster](http://en.wikipedia.org/wiki/Ion_thruster)

------
noonespecial
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.

~~~
Wingman4l7
True, but their original goal was 4x this amount.

~~~
guiambros
I just attended a meet-up this evening with Slava Rubin, Indiegogo's CEO, and
that was one of the topics he covered during his talk. The psychology of
crowdsourced projects is fascinating.

Basically the analogy is that if you want to raise 100, you set your goal to
50, and will probably end up with 120. Now if you set your goal to 100, you
may end up with 20 and a failed campaign. Same project, same pitch, same
perks.

Of course this is not exact science, but you got the idea. The special advice
is to figure out the number that you _need_ (versus what you _want_ ), and
make sure you can cross the 1/3 of the funding early on.

Lots of things come into play: initial inertia, exposure, acceleration as you
get closer to your goal, resistance around 1/3, etc.

~~~
noonespecial
"People only back winners." If people think that there's no way they'll ever
reach that ambitious goal, they won't contribute, so there will be no way
they'll ever reach that ambitious goal.

~~~
andrewfong
The irony is that Kickstarter's design ensures you won't lose any money
backing a loser. In theory, backing a loser should be a risk-free proposition,
but folks clearly don't see it that way.

~~~
ramblerman
If you define a loser as a kickstarter that doesn't reach 100% funding, you're
right

The OP you're responding to though defined a loser as someone who has
unattainable goals in the eyes of the people. In which case you can certainly
lose your money.

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alanctgardner2
> 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 with the other commenters in asking
why this needs money from outside the traditional channels. It's the kind of
long-winded and technical writeup I would expect from a grant proposal, not a
Kickstarter.

~~~
maaku
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.

------
sherjilozair
I don't understand. $50K being asked by professors and PhD students? They
certainly enjoy funds orders of magnitude more. $50K is like two YC startups'
seed money.

Why do they want it? Can't they self-fund it? Or do they just want other
people to share the glory? Isn't the equipment shown in the video worth as
much, or probably more?

~~~
notahacker
$50k is also a rounding error in the budgets of national space agencies and
private sector players in the space industry, many of whom might be interested
in a magical and revolutionary propulsion technology that could - if possible
to extend to larger satellites - dramatically increase the design life of
existing satellites and reduce the risk of failing to attain the desired
orbit.

~~~
robotresearcher
The piles of money at NASA, DOE, etc. are already allocated to things. They
employ a lot of people on strategic projects. There is extreme competition for
the small fraction that is available for new bids at any one time.

------
ThomPete
Off-topic

I have seen even Nasa uses Spaaaaaace as a word.

Anyone have an explanation?

~~~
iharris
Portal 2 reference:

[http://www.youtube.com/watch?v=xeKMS62GrTI](http://www.youtube.com/watch?v=xeKMS62GrTI)

Edit: It's clear that _someone_ in NASA is a Portal fan - they sent a laser-
etched image of Wheatley up with an HTV-3 resupply craft:

[http://www.escapistmagazine.com/news/view/118637-NASA-
Sends-...](http://www.escapistmagazine.com/news/view/118637-NASA-Sends-
Wheatley-Into-Spaaaace)

~~~
ThomPete
Their menu items on the left are even spelled that way.

[http://www.nasa.gov/content/blue-origin-test-fires-new-
rocke...](http://www.nasa.gov/content/blue-origin-test-fires-new-rocket-
engine/index.html#.Up46yWRDue0)

~~~
quarterto
Yeah, I'm pretty sure you're running a
[http://xkcd.com/1288/](http://xkcd.com/1288/) browser extension.

~~~
ThomPete
!!!!

Doh haha you are totally right. Completely forgot about it.

Thanks.

------
zellyn
I'm interested in this as a cheap way of providing time-limited encryption:
[https://news.ycombinator.com/item?id=6511690](https://news.ycombinator.com/item?id=6511690)

------
outworlder
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'.

~~~
acjacobson
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.

~~~
gus_massa
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.

~~~
XorNot
The other benefit is that you can find more water in space - it's harder to
find argon and harder still to put it in a usable form.

They're almost certainly thinking of what you could with ion thrusters, the
sun (or plutonium) and some of the icy bodies in the outer solar system.

------
embro
Just gave what I could! Hope this help!

SCIENCE!!!!!

------
vastinfest
This is a very cool idea indeed.

I looked over their Kickstarter and link to CAT engine itself, but only got
confused. How are they going to change direction of the craft itself (I'm not
sure what's the proper "space" terminilogy for "turning left or right is")? Or
that is not needed?

~~~
XorNot
In space you can just spin a gyroscope faster or slower to rotate. No wind-
resistance means you don't need a particularly heavy gyroscope to do it even.

------
Wingman4l7
It's worth noting that 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-...](http://www.kickstarter.com/projects/longmier/cat-a-thruster-for-
interplanetary-cubesats)

------
Taylorious
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?

~~~
Wingman4l7
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-...](http://www.kickstarter.com/projects/longmier/cat-a-thruster-for-
interplanetary-cubesats)

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-...](http://www.kickstarter.com/projects/longmier/cat-a-thruster-for-
interplanetary-cubesats/posts/561108)

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

~~~
tlarkworthy
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)

------
tocomment
Would something like this be able to work within the atmosphere?

~~~
InclinedPlane
In a word: no. It generates a very minute amount of thrust. That's ok in the
freefall of space because acceleration running 24/7 adds up fairly quickly.
But these thrusters won't have a thrust to weight ratio higher than 1 so they
can't feasibly be used for in atmospheric flight.

~~~
tocomment
But couldn't a version be built on the same principles that has higher thrust?

~~~
Pinckney
Ion thrusters have atrocious thrust to weight ratios. You can slap more ion
thrusters on, but that adds mass linearly. You can't scale up voltage much, or
you get current arcing across the acceleration region, and you can't add more
ions, because they'll interfere with each other. As far as I'm aware, there
aren't any designs that have thrust-weight ratios anywhere near 1.

(For perspective on just how much this would need to scale up, the CAT
thruster developes 2mN thrust [0.00045 lbf] on a spacecraft that weighs 2.5kg
[5lbs] without fuel.)

In any case, if you're flying in atmosphere, you can probably extract your
propellant directly (or just use propellers). The whole point of ion engines
is that they're fantastically efficient. This is important when you need to
carry all of your reaction mass along with you (and your mass ratio scales up
exponentially as a function of delta-V), but not important when you're flying
through atmosphere (and surrounded by reaction mass).

------
nayshins
Sending my name to deep space... FOR SCIENCE!

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nullcode000
Backed. Thanks for sharing the project.

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

~~~
dnautics
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.

------
el_shayan
Why does it feel so much like a scam?

~~~
DrStalker
Because they don't explain the technology very well.

It looks similar to an ion thruster which is a technology already in use in
space for situations you have plenty of power from solar panels, a long way to
go to get somewhere, and your biggest concern is saving on weight by not
carrying much fuel.

I don't see any fundamental reason it can't work, just questions as to how
well it will work and if it will be better than existing technology.

------
ape4
Only $50K ?

