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Science and Technology "Somewhere, something incredible is waiting to be known." - Carl Sagan.

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Old June 29 2011, 08:13 PM   #31
STR
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Re: The DARPA 100 Year Starship

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.
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Old June 29 2011, 08:57 PM   #32
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Re: The DARPA 100 Year Starship

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.
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Old June 29 2011, 10:50 PM   #33
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Re: The DARPA 100 Year Starship

^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".
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Old June 30 2011, 01:58 AM   #34
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Re: The DARPA 100 Year Starship

sojourner wrote: View Post
^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)


STR wrote: View Post
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.
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Old July 9 2011, 12:46 PM   #35
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Re: The DARPA 100 Year Starship

sojourner wrote: View Post
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.

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Old July 9 2011, 12:50 PM   #36
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Re: The DARPA 100 Year Starship

Yminale wrote: View Post
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.

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Old July 9 2011, 08:46 PM   #37
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Re: The DARPA 100 Year Starship

RAMA wrote: View Post
sojourner wrote: View Post
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.
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Old July 10 2011, 03:39 AM   #38
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Re: The DARPA 100 Year Starship

sojourner wrote: View Post
RAMA wrote: View Post
sojourner wrote: View Post
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...
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Old July 12 2011, 04:36 AM   #39
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Re: The DARPA 100 Year Starship

America probably won't be around in a 100 years
You sound like Al Qaeda's wishful thinking..
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Old July 12 2011, 11:51 PM   #40
John O.
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Re: The DARPA 100 Year Starship

MANT! wrote: View Post
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.
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Old July 12 2011, 11:57 PM   #41
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Re: The DARPA 100 Year Starship

Heck, stop the trains for a week and see what happens.
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Old July 13 2011, 01:33 AM   #42
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Re: The DARPA 100 Year Starship

sojourner wrote: View Post
Heck, stop the trains for a week and see what happens.
California has had many budget issues over the years, until the budget is passed, many state workers (including law enforcement) were provided with I.O.U.s instead of actual paychecks..some banks didn't honor the IOUs..so those workers effectively didn't get paid... Yet, the system didn't collapse..and riots didn't happen..folks just protested and told the elected representatives to do their jobs...


The infrastructure isn't as "fragile" as folks think it is...

without a natural disaster to eliminate governmental control, the system works very well...
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Old July 13 2011, 05:33 AM   #43
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Re: The DARPA 100 Year Starship

^Stop the trains for a week and people starve.
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Old July 13 2011, 11:40 AM   #44
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Re: The DARPA 100 Year Starship

NOT unless you can stop the trucks...
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Old July 13 2011, 06:24 PM   #45
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Re: The DARPA 100 Year Starship

The trains feed the distribution centers where the trucks load up.
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