The DARPA 100 Year Starship

[MANT!]

I do like the *First one needs to have a destination* aspect of the project..
once the destination is found, the political and financial backing would be easier.

Also taking the long term approach is far better than any "Get There Now" as total costs (though high) would be spread out over a much longer period of time, making budgeting much easier.

the matter of interstellar flight can take several tacks.. a new propellant source or crude use of power..

http://en.wikipedia.org/wiki/Project_Daedalus
http://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

http://en.wikipedia.org/wiki/Project_Longshot

as designs already exist for crude interstellar spacecraft, it only makes sense that a destination needs to be found first...

 

[John O.]

I agree, another aspect this symposium will certainly have to tackle is that we can't just rely on ideas that may be technologically sound but pragmagically inviable. A pulsed nuclear propulsion system would require too many nuclear detonations to ever work, unfortunately, unless somehow the political climate about it were to change drastically or some powerful and influential politician were to get it into his head to make it possible..

 

[sojourner]

Pulse nuclear will never be politically viable near earth. Once we branch out into the solar system though, it may catch on.

 

[John O.]

Pulse nuclear will never be politically viable near earth. Once we branch out into the solar system though, it may catch on.

Yeah but we would have to be so branched out that even testing could be done at a safe distance, if the political environment about nuclear detonations remains the way it is.

Actually I think the idea of even building warheads again, for any purpose, would be difficult to sell, in part because it involves rebuilding a lot of government infrastructure associated with nuclear arms construction and there'd be a hoopla over that.

 

[sojourner]

^well, I could see a scenario where the warheads are built off earth. I don't think nuclear pulse will ever be allowed near earth. period.

 

[Yminale]

Uhm you do all know that this is a PR (and possible recruitment) even. DARPA is not serious about building a starship (America probably won't be around in a 100 years)

 

[sojourner]

^Nope, didn't know that at all..

DARPA isn't building anything. If you read the site you'll see that it's just a study in how to develop a path to develop the technologies needed to eventually build a ship.

 

[STR]

Actually I think the idea of even building warheads again, for any purpose, would be difficult to sell, in part because it involves rebuilding a lot of government infrastructure associated with nuclear arms construction and there'd be a hoopla over that.

As far as I'm aware, they never really disassembled much of the warhead building infrastructure. You actually need a fair amount of infrastructure to maintain and refurbish existing warheads. In fact, it appears that they've recently begun replacing older structures with new ones, like the "Kansas City Plant" which makes electronic and mechanical components for warheads.

 

[STR]

DARPA isn't building anything. If you read the site you'll see that it's just a study in how to develop a path to develop the technologies needed to eventually build a ship.

Correct, it's a technology symposium - DARPA's just organizing it.

Yeah they've already had a deadline asking for "Requests for Information" in which they want people to submit ideas for how such a 100 yr organization might be built, funded, sustained, etc.

Also, I sent it on to my PhD advisor - he's given me the green light to submit our research abstract and present if it's selected, woot!

Are you allowed to tell the general public (schmucks like the rest of us on this board) a little bit about your proposal? I'm curious.

We take a helicon (which is a tube of plasma excited to extremely high ionization by a specifically tuned RF signal wound around a coil of electromagnets surrounding the tube), use it as a plasma source and inject that plasma into an IEC (which is an experimental fusion device). The motivation was that while fusion does not currently take place to any appreciable degree inside an IEC, it has a mode that's known to act as a plasma jet. In physics research they use what's called the 'star mode' of operation - and jet mode was always avoided because it destroys the internals of the IEC if you don't modify it to allow for the jet to exhaust. If you build a channel (as we have) to allow the jet to exhaust, then it can potentially produce thrust.

In the current evolution, it isn't a candidate for interstellar propulsion - but it is most definitely a candidate for satellite, trans-lunar injection and interplanetary propulsion. Isp is in the 4000-200,000 range depending on power levels and efficiencies we still have to work out. Nobody has modeled the electrostatic field in jet mode in an IEC before because it was of no interest, so that's a mystery right now as well. But at present the leading electric propulsion thruster is the Hall Effect Thruster and we think we can out-perform it - plus, the Hall thruster almost always has to use Xenon, which is becoming increasingly expensive and is absolutely not an option for interstellar travel because of the extremely large quantities it would require.

Actually just last week we got it to fire in jet mode briefly. There are still a lot of unknowns regarding the right conditions to fire in jet mode. Man it was a thing of beauty!

In the future, it may be possible to further develop the IEC concept such that you get fusion taking place and you get a much, much, MUCH hotter plasma coming out (i.e., higher velocity - higher thrust and ISP) in which case it is a candidate for interstellar propulsion.

Minus the fusion aspect, the helicon->IEC coupling is similar to VASIMIR but a lot mechanically simpler.

Here's a picture but this was just before we got it into jet mode. What you're seeing is a ball of argon plasma (the blue ball) inside a concentric electrostatic grid (the atom looking metal rings), with a hole to allow the plasma to escape the potential well in a specific direction. Unfortunately, it's not quite a jet there, it's diverging into a diffuse spray. As a jet it's a very narrow tight beam with what we believe may be shock patterns like you see in compressible flow.

Thanks! I was a bit confused until I realized you were talking about a Polywell. Interesting stuff. Do you need a self-sustaining fusion reaction to make this a viable space motor?

 

[John O.]

Actually I think the idea of even building warheads again, for any purpose, would be difficult to sell, in part because it involves rebuilding a lot of government infrastructure associated with nuclear arms construction and there'd be a hoopla over that.

As far as I'm aware, they never really disassembled much of the warhead building infrastructure. You actually need a fair amount of infrastructure to maintain and refurbish existing warheads. In fact, it appears that they've recently begun replacing older structures with new ones, like the "Kansas City Plant" which makes electronic and mechanical components for warheads.

Cool, I didn't know that. That's encouraging, actually.

I was actually thinking about also presenting on antimatter catalyzed thermonuclear pulsed propulsion on my own, I did some research on that a few years ago as well, but I doubted its political viability.

DARPA isn't building anything. If you read the site you'll see that it's just a study in how to develop a path to develop the technologies needed to eventually build a ship.

Correct, it's a technology symposium - DARPA's just organizing it.

Are you allowed to tell the general public (schmucks like the rest of us on this board) a little bit about your proposal? I'm curious.

We take a helicon (which is a tube of plasma excited to extremely high ionization by a specifically tuned RF signal wound around a coil of electromagnets surrounding the tube), use it as a plasma source and inject that plasma into an IEC (which is an experimental fusion device). The motivation was that while fusion does not currently take place to any appreciable degree inside an IEC, it has a mode that's known to act as a plasma jet. In physics research they use what's called the 'star mode' of operation - and jet mode was always avoided because it destroys the internals of the IEC if you don't modify it to allow for the jet to exhaust. If you build a channel (as we have) to allow the jet to exhaust, then it can potentially produce thrust.

In the current evolution, it isn't a candidate for interstellar propulsion - but it is most definitely a candidate for satellite, trans-lunar injection and interplanetary propulsion. Isp is in the 4000-200,000 range depending on power levels and efficiencies we still have to work out. Nobody has modeled the electrostatic field in jet mode in an IEC before because it was of no interest, so that's a mystery right now as well. But at present the leading electric propulsion thruster is the Hall Effect Thruster and we think we can out-perform it - plus, the Hall thruster almost always has to use Xenon, which is becoming increasingly expensive and is absolutely not an option for interstellar travel because of the extremely large quantities it would require.

Actually just last week we got it to fire in jet mode briefly. There are still a lot of unknowns regarding the right conditions to fire in jet mode. Man it was a thing of beauty!

In the future, it may be possible to further develop the IEC concept such that you get fusion taking place and you get a much, much, MUCH hotter plasma coming out (i.e., higher velocity - higher thrust and ISP) in which case it is a candidate for interstellar propulsion.

Minus the fusion aspect, the helicon->IEC coupling is similar to VASIMIR but a lot mechanically simpler.

Here's a picture but this was just before we got it into jet mode. What you're seeing is a ball of argon plasma (the blue ball) inside a concentric electrostatic grid (the atom looking metal rings), with a hole to allow the plasma to escape the potential well in a specific direction. Unfortunately, it's not quite a jet there, it's diverging into a diffuse spray. As a jet it's a very narrow tight beam with what we believe may be shock patterns like you see in compressible flow.

Thanks! I was a bit confused until I realized you were talking about a Polywell. Interesting stuff. Do you need a self-sustaining fusion reaction to make this a viable space motor?

We don't think so, no. Right now the math tells us that if the ions are coming out in a beam they will be highly energetic, enough to make it an extremely lucrative electric thruster to fill the gap between high-Isp Hall Thrusters and high thrust rocket motors. The "make or break" engineering problem right now is making sure it's in fact a neutral ion beam and not an electron beam. Electron beam = no appreciable thrust whatsoever (plus charge disparity issues). It may take some tweaking of the IEC to ensure it's a neutral ion beam.

 

[STR]

Thanks, just a couple more Q's. Really interesting stuff, though the engineering is beyond this MBA student.

Would you even be able to use the IEC as a fusion reactor while it's being used as a motor?

Also, regardless of power source, how many kW of power would you need to sustain the thing? I know enough that RF is a decently efficient way to heat things up, but I have no clue what it takes to get plasma temperatures.

 

[Ronald Held]

Our government cannot have steady spending for more than a few years, so 100 year plans will not work until the US( and world )can engage in long term projects.

 

[sojourner]

^Which is the whole point of the project. It's not "how to build a ship", it's "how to build a sustainable program on a long term basis".

 

[John O.]

^Which is the whole point of the project. It's not "how to build a ship", it's "how to build a sustainable program on a long term basis".

Exactly, I think it's a foregone conclusion that one of the goals of this symposium and future movements are to figure out how to make it self sustaining (think Men in Black funding itself through space technology patents, lol)

Thanks, just a couple more Q's. Really interesting stuff, though the engineering is beyond this MBA student.

Would you even be able to use the IEC as a fusion reactor while it's being used as a motor?

Also, regardless of power source, how many kW of power would you need to sustain the thing? I know enough that RF is a decently efficient way to heat things up, but I have no clue what it takes to get plasma temperatures.

1st Q - there's plenty of varying opinions on that. Some would argue quite ardently that in 30 years of trying, the IEC has not shown itself to be a promising potential environment for any significant amount of fusion to take place. Others disagree. I think the central point is that even if it never does, and the IEC functions as nothing more than an ion accelerator - in a sense, you could think of it as an electrostatic nozzle (versus the VASIMIR's magnetic nozzle), it still represents the potential for a very useful thruster compared to modern electric thrusters that are out there (Hall, Ion).

2nd Q - it's not so much an issue of needing a lot of power to sustain the engine - what you're talking about when ur talking about sustaining the engine is in fact just making sure the helicon ignites a plasma and the IEC fires too, which has more to do with striking the right pressure / gas flow rate balance. There are minimum values the voltage on the IEC grid to get ignition, and RF power to get a plasma, but they're low.

In other words, the engine doesn't have exceptionally high power requirements for missions like satellites - but if you wanted a big ole engine to get u to Mars, you are probably talking about needing anywhere from 2 kilowatts to... whatever you could generate. I mean as far as we can tell, it continues to scale upward without loss of efficiency in terms of power. I mean the point of increasing RF power is to get a higher plasma density (higher ionization fraction), but by the helicon's very nature it actually produces a very high ionization fraction (like .9) - hence recent (last 2 years) widespread interest in it as an ion source for propulsion systems, because that's much higher than previous ion production methods. In case it's not immediately clear, higher plasma density is desirable because in the IEC environment, only charged particles (ions) do you any good; neutral particles are useless. In academic discussions of modern electric thrusters this is not always made clear, but one of the major failings of electric propulsion systems to date has been a lack of an ability to generate a high ionization fraction, and the corresponding efficiency loss is termed "propellant utilization efficiency" which is often no higher than .6 or .7 in ion and hall thrusters, because the process of ionization is in fact, a somewhat difficult and high-energy process (conventionally). That's what's so cool about the helicon.

Now, power in space is potentially hard to come by, but solar arrays are really taking monumental steps forward. I did a really large photovoltaic report recently (some may remember I asked for PV specs on Juno and Phoenix) and Dawn produced about 2.5 kW for its ion engine; Juno's array will produce (launches in August 2011) about 15 kW in LEO and ~500 W at Jupiter. That is really pretty remarkable, and it's not simply a giant array - it's large but it also represents a couple of fundamental leaps forward for PV technology. It's kind of a rare island of prosperity in the space industry in that there are 2 high dollar sources of funding for PV use - both the growing international and domestic interest in clean energy technology (which is gradual but ever present), and secondly and probably a more significant short term boon for the tech, is the fact that every single satellite going up today - whether it's for telecom, military, academic, whatever - has to rely on solar for power, so there's a tremendous interest in the private sector to reduce costs and improve efficiencies. Lot of money going into it, which is going to help make some of these next-gen electric propulsion systems become more viable.

 

[RAMA]

DARPA isn't building anything. If you read the site you'll see that it's just a study in how to develop a path to develop the technologies needed to eventually build a ship.

Doesn't matter, its going to take 100 years of organizing, planning, testing and building to get such a starship going. Our problem on Earth is usually short-sightedness, the fact that there is even money involved now is a good sign to me.

RAMA

 

[RAMA]

Uhm you do all know that this is a PR (and possible recruitment) even. DARPA is not serious about building a starship (America probably won't be around in a 100 years)

Why? The US is is more stable than any nation on the planet. Its the most adaptable, diverse....these are good qualities to have, and ones that many supposed "empires" that did not last didn't have. Even if the world is more united in 100 years, I'd expect the US to be a strong component. The strange idea some people have that the US is at the end of its infleunce is one of the most ludicrous I've seen, and very likely just wishful thinking ifrom certain parts of the world.

RAMA

 

[sojourner]

DARPA isn't building anything. If you read the site you'll see that it's just a study in how to develop a path to develop the technologies needed to eventually build a ship.

Doesn't matter, its going to take 100 years of organizing, planning, testing and building to get such a starship going. Our problem on Earth is usually short-sightedness, the fact that there is even money involved now is a good sign to me.

RAMA

What "doesn't matter"? Did you respond to the wrong person here? Because you seem to be agreeing with my post. DARPA realizes it will take 100 years. That's what this study is about. Developing an organization that can last that long to achieve it's goal.

 

[RAMA]

DARPA isn't building anything. If you read the site you'll see that it's just a study in how to develop a path to develop the technologies needed to eventually build a ship.

Doesn't matter, its going to take 100 years of organizing, planning, testing and building to get such a starship going. Our problem on Earth is usually short-sightedness, the fact that there is even money involved now is a good sign to me.

RAMA

What "doesn't matter"? Did you respond to the wrong person here? Because you seem to be agreeing with my post. DARPA realizes it will take 100 years. That's what this study is about. Developing an organization that can last that long to achieve it's goal.

It doesn't matter they're not actually building the ship, as many people are reading into this. Yes we are agreeing...

 

[MANT!]

America probably won't be around in a 100 years

You sound like Al Qaeda's wishful thinking..

 

[John O.]

America probably won't be around in a 100 years

You sound like Al Qaeda's wishful thinking..

pft. If we're not around it won't have anything to do with al qaeda. Our social infrastructure is more fragile than people think. Stop paying cops & emergency services workers and see what happens.