Launch a Water-Propelled Satellite into Deep Space | Hacker News Reader

Launch a Water-Propelled Satellite into Deep Space

kickstarter.com

145 pointsmrchucklepants61 comments

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 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

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

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/Ion_thruster

Upon reading the entire page, it looks legit. But when the page first loaded, I read "propelled by water" and immediately thought "Uh... aren't normal rockets also propelled by water?" I just think the kickstarter page could have been a little more upfront about the plasma part.

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

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.

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.

"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.

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.

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.

I think part of the problem is that deciding to be a backer has a mental cost (decisions are painful). If a project has a very low chance of success, perhaps the cost of the process of decision making outweighs the small chance of a potential gain.

I'm trying to figure out how to hack this psychology. I'm starting at 1/10 what I NEED, and running it into a phase II. That way we can declare an initial victory to capture the 'people like to back a winner' and then leverage the donor network to go the whole way.

Keep in mind the psychology cuts both ways. While people don't want to back a loser, I can imagine some people (particularly geeks and alpha types) would avoid backing what they feel that has "jumped the shark".

Using my initial analogy, if you need 100, setting your goal to 5 may not be the wisest move, as you may face resistance when you get to multiple times your goal. After you get to, say, 55, you'll be already 1000% over your target, but still largely behind your real need.

It's like the sharing psychology - what matters is if it will make you look good. You don't share with your friends on FB that YouTube video with 50 million views. You'll feel like the last person on earth to discover it.

I'd bet the same happens on crowdfunding projects.

Sounds like a really interesting talk -- do you know if it was recorded & posted anywhere?

Yes, the talks were recorded, but sadly it takes a few weeks (sometimes months) to be posted online.

Keep an eye on Hardwired NYC @ http://hardwirednyc.com/videos/

> 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.

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.

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?

Why do people think funding science is easy?

"They certainly enjoy funds orders of magnitude more."

Certainly? If they had the money already they wouldn't be asking for it. Perhaps they have had this proposal declined once or twice by the agencies. Science is very competitive and the majority of proposals are not successful: 10% acceptance rates are not unusual. It's also highly winner-take-all since winning funding tends to generate output which tends to attract more funding.

"$50K is like two YC startups' seed money."

Which is loaned in expectation of a return. Science funding is a gift in the hope of a long term strategic advantage. The government doesn't just hand out $50K to Prof. Doe on request. Besides, $50K would barely support one PhD student-year with 50% overhead and tuition.

Researcher profs spend a large proportion of their time on grant writing and only the best are successful, and while it does come in large chunks when it comes (in the US), the expected value of each application is not high. It's much easier for the currently in-vogue fields than others. It's also hugely easier if you have a little industrial funding, as there are many matching programs. This means getting the attention of the industrial players, if there are any in your field. Very time consuming!

$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.

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.

"While we have obtained some external funding, this mission may never happen without your help."

I suppose I get it, but I thought Kickstarter campaigns required a deliverable end result as a result of contributions?

What do you mean by deliverable? "There will be a camera for science" is an end result.

He means a link between, you donate, they make product. You donate, they achieve X with your money. This one reads more like, "We have vague plans and lots of money but we need more, please contribute to our slush fund".

As best I can tell, the direct impact of the kickstarter funds will be paying for a camera to put on a launch vehicle to watch the CAT engine, but it's not very clear.

You said it better than I could. Exactly this.

Off-topic

I have seen even Nasa uses Spaaaaaace as a word.

Anyone have an explanation?

Portal 2 reference:

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-...

I'm not sure, but I suspect that the Portal 2 reference might itself be a reference to the recurring Muppet Show sketch "Pigs in Space" (pronounced Piiigs innn Spaaace).

https://www.youtube.com/watch?v=tYjbkRktqIE

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

http://www.nasa.gov/content/blue-origin-test-fires-new-rocke...

Yeah, I'm pretty sure you're running a http://xkcd.com/1288/ browser extension.

!!!!

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

Thanks.

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

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.

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.

Xenon is actually pretty expensive.

http://boards.straightdope.com/sdmb/showthread.php?t=581982

Just gave what I could! Hope this help!

SCIENCE!!!!!

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?

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.

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-...

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-...

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)

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

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.

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

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).

Space is the only place where these engines are of any practical use; a combination of endless solar power, no friction, not having to stay up in the air by constantly fighting gravity and huge distances to travel means an engine with a tiny amount of thrust that can run for long periods of tiny with a tiny amount of fuel is useful.

On earth you're likely not even going to be able to overcome friction and start moving.

It will require correspondingly more power, and then the mass of power supply will be a problem.

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

Backed. Thanks for sharing the project.

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.

Why does it feel so much like a scam?

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.

Only $50K ?

Reply on news.ycombinator.com