Zubrin claims VASIMR is a hoax

The efficiency may be high but, when you must go some-where in a hurry, you want sustained high thrust rather than an ion-engine's 'whisper'...

Zubrin has a point. Nuclear power, and shielding, just isn't economical for space flight. A different power source would make the Vasimir system practical, with a small MHD power take off. Chang-Diaz has done good work, Zubrin has done good work. Let us reserve "Hoax" for the cold fusion fraudsters, and return to the more correct "impractical as currently proposed" to describe this important work.

I agree with both of the previous comments.

Mars in 39 days isn't going to happen with any current tech.

I would like to point out one idea that 'could' hold promise, IF someone figures out how to do it. Beamed power would kill two birds with one stone, supplying power and eliminating the above concerne about power to weight ratio of the power supply and fuel. You could station any number of different power generators at Lagrange points along whatever path you choose to reach Mars. Size and efficiency cease to matter that way. Solar panels with onboard kinetic storage could collect and store power for months prior to when the energy is needed to be beamed to the spacecraft. As unlikely as it may seem, due to how logistically complicated it would be, beamed power may be more likely than interplanetary shuttles with conventional on-board power supplies.

Solar panels actually have slightly better power-weight ratios than any proposed nukes with detailed designs, at least in the inner solar system, including Mars. 1kW/kg is quite feasible. The supporting structure need only deal with a few % of 1 gravity at most, usually far less. An array of a couple hundred meters on a side massing less than 20 tons should give over 20MW, which is I think a more likely needed figure than Zubrin's claimed 200MW. For larger powers, a mostly solar-thermal approach (with some PV) using film concentrators and liquid-droplet radiators might be lighter and more effective

When pontificating against ideas he doesn't like, Zubrin likes to run the numbers on strawman designs, bad implementations, then claim he proved their impossibility.

Zubrin has a point. Nuclear power, and shielding, just isn't economical for space flight.

Yep, the Pioneers, Voyagers, Galileo and Cassini have failed so badly because of all that nasty nu-cu-lar power.

On the 39 days to Mars claim, Zubrin says VASIMR would need to couple with a nuclear reactor system with a power of 200,000 kilowatts and a power-to-mass ratio of 1,000 watts per kilogram, while the largest space nuclear reactor ever built, the Soviet Topaz, had a power of 10 kilowatts and a power-to-mass ratio of 10 watts per kilogram.

What about SAFE-400? 100 kWe at 1200 kg, that makes it almost 0,1 kW/kg. We have hardly scratched the surface of what is possible with nuclear in space, and I dont think any other energy source will have the energy density to get us further than Mars and/or count travel time in weeks instead of years than nuclear (fission or possibly fusion).

http://en.wikiped...n_Engine

I would like to point out a couple things to a few of you guys to clear up this situation.
1)Solar power is fine to an extent, but it would be difficult to get enough solar power for that kind of need. Plus, it becomes less and less feasable as you go out. Very few, if any, spacecraft past the asteroid belt have used solar power.
2) It's ridiculously ludicrous to compare the nuclear power plant needed with current spacecraft nuclear plants. They all use radioactive decay generators, rather than a full nuclear heat reactor, like this would require.
3) Shielding on the nuclear reactor? Are you stupid? The only part that would need to be shielded would be a small cross section between the reactor and the crew cabin - the rest of the radiation is fine just going off into space. But consider that they will already need to have shielding in place for space radiation...

As for Vasimir...it seems like it is valid. However, if he's right and it can't sustain power, then too bad :(

3) Shielding on the nuclear reactor?

Also, there will be lots of fuel, and possibly quite long distance between the crew and the reactor. I would be more concerned about the mass of the radiators than the shielding, tough. That may prove to be a problem, may it not?

From what I've read, it would be a fairly massive reactor in space terms. it's accounted for in the spacecraft designs, however it is a bit of a lift for a rocket. Plus, people are pretty nervous about ANY nuclear reactor going into space, much less a Full Size one.

Perhaps a fuel efficient thorium design would be a good compromise, but it doesn't fully alleviate either of the two issues I just stated above.

None of which employ nuclear reactors.

"Yep, the Pioneers, Voyagers, Galileo and Cassini have failed so badly because of all that nasty nu-cu-lar power." - ShootisTard

"1,000 W/kg Solar Concentrator Arrays for Far-Term Space Missions" by Mark J. O'Neill of ENTECH, Inc., Presented at the Space Technology & Applications International Forum (STAIF 2004) Albuquerque February 2004, published by the American Institute of Physics
http://slasr.com/...IF04.pdf

Hundreds of watts/kg now, detailed designs for 1000W/kg by 2022.

The power available in Mars orbit would be 36% to 52% of that near-earth, which is good enough.

None of which employ nuclear reactors.

"Yep, the Pioneers, Voyagers, Galileo and Cassini have failed so badly because of all that nasty nu-cu-lar power." - ShootisTard

But he didn't say nuclear reactor. He said nuclear power. Which all of them use. Please vendicar, reading. comprehension. skills.

The numbers Zubrin is using might come from the following report from MIT. Here are some quotes:

To go to Mars and beyond,100-400 kW thrusters are needed

Note that he said thrusters, not kW of electric power.

Currently,there is no way to fulfill an electric ion thrusters power requirements in space.
Solar cell arrays are heavy and would not receive enough sunlight in deep space. A small
nuclear fission reactor (less than 1 MW) would meet this power requirement, but reactor thermal energy needs to be processed by power converters to create electric power

That's where the problem starts.

A helium Brayton cycle for terrestrial power plants
achieved 43% efficiency at 1073 K [8]. By comparison,to days best coal power plants are
35-40% efficient

but that isn't what you need for space

Heat cycles in space present a major difficulty. Since there is no matter in space,ra diation
is the sole option for releasing thermal energy

continued:
So, you end up needing a much larger and more complicated system than just the basic need for 100-400 kW of thrust. There is efficiency loss from the reactor to the generator. Then there is additional loss from the generator to the engine. You must produce much more power at the reactor than you end up with at the thrust nozle. The waste power which is lost between the reactor and the thrust nozle must be radiated somehow or the whole thing melts. He goes on to explain that the idea is feasable, but will require substantial research into system components such as an ideal gas turbine which operates at a much higher temperature than what we currently have. Here's a link to the MIT paper I quoted:
http://web.mit.ed...ianr.pdf

So, in regard to the above mentioned SAFE-400, yes, that could work, but you would need more than one of them, in addition to several high temperature generators which do not exist yet, as well as some kind of heat radiator that is not too massive, which also doesn't exist yet. The level of mechanical complication and the number of moving parts in such a system would make the whole thing EXTREMELY risky. Any nation to attempt such a venture would need to be prepared for tragic failures and human loss in the process. I don't think the US would tollerate it currently, though that is a shame. Volunteers would line the streets regardless of risk. Then there's still the risk of launching highly enriched nuclear fuel into orbit, where you would need to assemble the ship prior to starting the journey to Mars. The overall cost would require a major multinational commitment over many years with a high risk of failure.

It's easier to just use chemical rockets.

All good reasons to colonize the moon. Available volunteers, plenty of turf for uranium processing, no atmosphere to pollute or lower the efficiency of photo-voltaics, water available for reaction-mass, lower escape velocity, and probably enough uranium to mine and process.
Moon first. Then Mars and beyond.

Moon or Mars are possible and have been since the sixties. The fact that we have been stuck in LEO for so long is depressing.

The VASIMR plasma rocket is an awesome concept, but I think it will work better just in deep space. I believe during launch would be better phase-shift plasma turbine using atmospheric gases as propellant. www.youtube.com/w...xPghXTCg

So, in regard to the above mentioned SAFE-400, yes, that could work, but you would need more than one of them, in addition to several high temperature generators which do not exist yet, as well as some kind of heat radiator that is not too massive, which also doesn't exist yet. The level of mechanical complication and the number of moving parts in such a system would make the whole thing

Heres looking ahead to efficient solid state thermoelectric materials... and high temp superconductors. Soon enough.

The VASIMR plasma rocket is an awesome concept, but I think it will work better just in deep space. I believe during launch would be better phase-shift plasma turbine using atmospheric gases as propellant. http://www.youtub...xPghXTCg

No electric/ion/plasma thruster has the power to launch anything. Their advantage is that they are efficient. They have no where near the power needed to overcome the earth's gravity. They are meant for space travel only.

"But he didn't say nuclear reactor. He said nuclear power. " - That Guy

If you know of a way of getting substantial amounts of power from nuclear reactions without using a nuclear reactor, tell us about it....

Thanks, Zubrin, for publicly questioning VASIMR.

In my opinion, government science has been seriously compromised by those who are willing to report anything that grant officer wants in exchange for grant funds.

I suspect that is the basis for the entire scandal about CO2-induced global warming.

Perhaps budget negotiations in Washington DC will restore sanity to government science.

Eisenhower warned of this potential problem in his farewell address on 17 Jan 1961:

www.youtube.com/w...ld5PR4ts

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo

"But he didn't say nuclear reactor. He said nuclear power. " - That Guy

If you know of a way of getting substantial amounts of power from nuclear reactions without using a nuclear reactor, tell us about it....

Vasimir will require a nuclear reactor. shootist was just saying that nuclear power has been used before. I was pointing out that what he said was correct.

Voyager and the other craft that use nuclear power currently use radioisotope thermoelectric generators. They use a direct electric conversion of the heat put off by radioactive decay through the use of thermocouples.

Antimatter propulsion

http://www.coloss...sics.pdf

If I've violated the rules for posting, sorry.

One more link on NLS propulsion

http://citeseerx....type=pdf

No electric/ion/plasma thruster has the power to launch anything. Their advantage is that they are efficient. They have no where near the power needed to overcome the earth's gravity. They are meant for space travel only.

There is the Magnetoplasmadynamic (MPD) Thruster that can be powerful enough to launch spacecraft, but it has a problem with degradation of cathodes. Hence, the Phase-shift Turbine can be equally powerful without problems.

Hoax is a too big word for vasimir, rather it seems that we have two fathers wanting to have trip to mars recognised as their own brainchild? What we really could use in space is a breakthrough in aneutric fusion, because that would do away with much shielding and dramatically improves the power to mass ratio, giving some oompf to the ion whisper

All these oil lobby folks and their love for chemical rockets...you can hear the audible 'ka-ching' of their mental cash registers salivating at the prospect of such an advocate of exploration trying to pick such an improbable winner of the mars ship propulsion contest. Chemical propulsion...preposterous...and expensive. The Chinese will pick a more practical approach, nuclear; and will not quail at building it. As for so called 'protest about the environment'...need I mention Tian-an-Men? They will not shrink from that either!.. a necessary action if we are to progress into space as a species. Diaz's invention does work and will work better. Of course a mirror fusion device would be nice, and generate power directly from electromagnetohydrodynamics via travelling wave superconducting coil assisted power recovery.

Try this one for size: Relativistic Phase Displacement Space Drive ... Go ahead, search for it on the big bad net. You WILL find it. Scary, huh!? and recent too. Guy does his math; who knows may have something. Neat video showing space warp possibilities on dnatube or something. Author IS given credit there.

You could station any number of different power generators at Lagrange points along whatever path you choose to reach Mars.

The problem is: Lagrange points aren't on that path.

Solar panels actually have slightly better power-weight ratios than any proposed nukes with detailed designs, at least in the inner solar system, including Mars.

Solar constant for Mars is less than half than what it is on Earth.

Yep, the Pioneers, Voyagers, Galileo and Cassini have failed so badly because of all that nasty nu-cu-lar power.

To be fair: these probes took a godly amount of time to get anywhere and didn't use the nuclear power for movement. A largish spacecraft (with humans aboard) that wants to use nuclear power in the megawatt range to get anywhere in an appreciable amount of time will probably need susbstantial shielding (albeit only in direction of the living quarters)

... What we really could use in space is a breakthrough in aneutric fusion, because that would do away with much shielding and dramatically improves the power to mass ratio, giving some oompf to the ion whisper

I suppose it could be:
1) Phase-shift Turbine to take off;
2) Chemical rocket aligned with Turbine to get into space; and
3) VASIMR to run away into deep space;
all that powered by clean and dense source of energy, He3 or p-B11 aneutronic fusion reaction.

The problem is: Lagrange points aren't on that path

Which path? Huh? The choices are nearly infinite. The L2 lagrange point is just outside earth's position, so you'll ALWAYS start near that one, unless YOU don't think you live on Earth? Then, depending on whether you are taking a leading or trailing trajectory, you will ALWAYS pass nearby either the L4 or L5 point. Then, if you decide that you want to loop around the Sun, you can also pass near the L3 lagrange. Your statement is complete incorrect.

Perhaps budget negotiations in Washington DC will restore sanity to government science.

Oh, would that be those brilliant political negotiators who begin their negotiation of budget shortfalls nearing the possibility of US default (becomming another Greece) with the statement "ANY tax increases AT ALL are OFF THE TABLE!"

Yeah, they should be able to solve things, Definitely. Perhaps you should go begging in Bejing for your Mars project funding?

So what RF frequency does a Plasma thruster like to operate with anyway? Why not simply microwave beam the power to the spacecraft at that frequency from the moon, or some high earth orbit solar power station which can see Mars continuously? A large array of microwave receiver antenna wouldn't weigh that much.

Beams tend to diverge over distance. The losses would be atrocious.

To get a very rough idea how much power we are talking about look at the amount of power used to send out messages from Mars and the amount of power received by dishes here on Earth (I just found the numbers for the Mariner probe (1965). Couldn't find exact numbers for more current craft). The difference then was 20 orders of magnitude(!)

If we (naively) use the same figure for power transmissions then we'd need to send out 100 quintillion Watts here to receive 1 Watt of power on Mars. That's about 100 million times what we currently produce on Earth (total).

So you see: Even if we shave a few orders of magnitude off that through more efficient transmission modes we're still far, far, FAR in the realm of fantasy when talking about 'beamed power' over interplanetary distances.

Which path? Huh? The choices are nearly infinite. The L2 lagrange point is just outside earth's position, so you'll ALWAYS start near that one, unless YOU don't think you live on Earth? Then, depending on whether you are taking a

Look at the wikipedia site on lagrangian points. The only relevant points for the 'beaming stations' you are proposing are the 5 Lagrangian points of Earth/Sun and Mars/Sun system. The former all about as far away to the Sun as Earth is and the latter are about as far away from the Sun as Mars is. But you always have the need to get from Earth orbit to Mars orbit. So no matter which path you choose The space between earth orbit and Mars orbit must always be traversed.

Even IF there were any stable points to put beaming stations at: I'd say it's easier to get one craft to Mars and back instead of putting a number of huge power plants into space and then having a slightly smaller craft travel the distance.

The thing that Zubrin is not focusing on is the fact that when we go to Mars we're going to want to get there more often and quicker so eventually tech like VASIMR is going to need developed anyway.

One trip to Mars every two years might be satisfying for the first trip but it's much too drawn out.

IMO the hydrogen fusion at nickel could make such engines feasible.

What Zubrin fails to understand is that his "Mars Direct" approach is both unaffordable and unstainable. The VASIMR and/or Ion drives powered by Concentrated Solar Power (CSP) is the only way to move out into the solar system in an affordable manner. The 12.5 concentration of the SLA simply want cut it, you need CSP at 1,000 suns. This can be done with a little commitment and funding. CSP at 1,000 suns combined with the VASIMR/Ion can take you anywhere in the solar system you want to go very cost effectively. You can even make it better by using wireless power transmission (WPT)and reduce the mass of your spaceships by a factor or 40 by removing the power system mass and replacing it with a low mass rectenna. This is the future of in-space transportation, so if you are not working on it you are working on the wrong technology. Zubrin is too in love with his on bad concepts to see the path forward.

But you always have the need to get from Earth orbit to Mars orbit. So no matter which path you choose The space between earth orbit and Mars orbit must always be traversed

The idea is not to completely replace the onboard fuel of the spacecraft. The power beaming ideas they are toying with would be more like an assist at the start (and maybe the end) of the journey. You would still have some kind of ion engine or something on the spacecraft, but you could significantly reduce the feul you would need. Clearly, such a system would only make sense if you planned regular trips, rather than a one shot deal. DARPA is already investigating an orbital system to beam power down to Earth, so the technology is already somewhat researched. A moon based linear accelerator launch assist might also be used for non-human spacecraft.

Beams tend to diverge over distance. The losses would be atrocious.

I always like to do a little research before I spout, you know to avoid looking silly. Why wouldnt anybody do this I wonder?

Obviously somebody thinks its feasible. Many variations. R&D is ongoing.

"A beam could also be used to provide impulse by directly "pushing" on the sail.

One example of this would be using a solar sail to reflect a laser beam. This concept, called a laser-pushed lightsail, was analyzed by physicist Robert L. Forward in 1989 as a method of Interstellar travel that would avoid extremely high mass ratios by not carrying fuel. His work elaborated on a proposal initially made by Marx. Further analysis of the concept was done by Landis, Mallove and Matloff, Andrews and others." -etc.
http://en.wikiped...opulsion

Well, instead of citing the cites from wikipedia I went and read some of them. I'll give you some excerpts from Landis to show you how ludicrous these designs are for even a SMALL probe (no humans aboard that)

Mileikowsky (1994), for
example, calculates the cost of a 1000 kg interstellar flyby probe
traveling at 0.3 times the speed of light. Analyzing the laser-pushed
lightsail propulsion system proposed by Forward (1984), 65,000 GW must be
supplied to the laser for 900 hours. At a capital cost of $2/W, the
electrical generation facility capital cost comes to 130 trillion (1.3
10^14) dollars.

Sounds a tad expensive.

Antimatter [Forward 1991] and particle-beam-pushed propulsion
[Landis 1989, Andrews 1993] systems, as analyzed by Mileikowsky, are even
higher in expense.

Oops.

In order to achieve the low divergence required,
the laser is focussed by a lens...the structure [lens],
although a third the diameter of the moon,...

Oh my. Yep. Realistic.

Not.

Then Landis goes on and tries to bring these costs/numbers down to several trillion dollars ... with highly speculative engineering solutions like, and I quote:

self-reproducing factories to produce solar cells

. He does manage to get the lens down to a diameter of just over 700km. Still a tad bit outside our possibilities just yet.

His work reads better than most science fiction - I have to give him that.

Then we run up against another fundamental problem: How do you brake a craft that is pushed by a lightsail? How do you reaccelerate it for the trip home? How do you immunize a flimsy light sail against microdebris?

And why the heck don't we spend a thousandth of that cost for some tech we already have to get humans there instead of a small cannister full of instruments?

I'm all for neat, new technology - but only the type that is even remotely realistic/sensible.

But I must admit, I did not do research on whether others thought this was feasible because I have taken laser lessons at Uni while getting my electrical engineering degree (those lessons having been in about 1998 or 99). There's some really basic physics involved in the divergence of a laser beam.

New metamaterials could actually improve that somewhat but they'd make for a slightly smaller, but MUCH heavier lens.

Your credentials are noteworthy. The paper you cite however
http://www.aleph....aser.txt

-is talking about interstellar distances, not inner system distances, which is what we were talking about, isn't it? I used the Forward article to indicate that the possibility had been explored.

For a mars trip your mirrors would be much smaller and your power needs much less, would they not? And additional options like capture/conversion for powered maneuvering and braking would make sense.

And it looks like their 1995 power gen $$ were for earth-based supply, not orbital. Am I missing something here auntialias?

For a mars trip your mirrors would be much smaller and your power needs much less, would they not?

I don't know about the 'much' since we were also talking about:
- manned flight
- with the ability to stop/land
- with return capability

and not
- a 1000kg probe
- one shot flyby (or at best orbital insertion - which is all that solar sails are good for ... at best)

How do you brake with a solar sail?

Even if you reduce the needed materials by a factor of 10 it's still ridiculously expensive and you'd need to put an enormous amount of material into earth orbit first instead of just doing it the conventional way.

And it looks like their 1995 power gen $$ were for earth-based supply, not orbital.

Yes. He notes that to set up 1W production capacity is about 2$ on earth. He also notes that to get the same production capacity in space costs about 1000$ which makes the problem even worse.

How do you brake with a solar sail?

Even if you reduce the needed materials by a factor of 10 it's still ridiculously expensive and you'd need to put an enormous amount of material into earth orbit first instead of just doing it the conventional way.

I think the article mentions that the sails can be made of voltaic material to capture and convert the beam? And as gswift mentioned these platforms will already be serving to transmit power to the surface. They will pay for themselves.

While at PPL I remember a post doc was working on a paper that described using a pellet stream. These pellets would be filled with fusion fuel for capture and use.

And as gswift mentioned these platforms will already be serving to transmit power to the surface. They will pay for themselves.

Hardly. Current power plants do not pay for themselves 500 times over (which is how good space based power plants would need to do to just break even with ground based counterparts - let alone be cost effective). We're already facing a multi trillion investment in converting from fossil/nuclear to alternative energy sources. If we do this with space based solar we'd be in the quadrillion range.

PV material gives you the ability to convert the beam to electricity. It does not give you the ability to magically shift about the impulse of the photons. For that you need another type of drive.

I remember a post doc was working on a paper that described using a pellet stream. These pellets would be filled with fusion fuel for capture and use.

This seems marginally more workable. But the fuel for fusion plants is actually very little compared to the weight of the fusion reactor.

From here: http://www.ccfe.a...aspx#Day

A large power station generating 1,500 megawatts of electricity would consume approximately 600 grammes of tritium and 400 grammes of deuterium each day.

With just over 3 and a half tonnes of fuel you could keep going for a decade. (For comparison: A craft the size of the space shuttle weighs about 100 tonnes - and for a 10 year journey you'd likely want to travel insomething substantially bigger)

Interesting article
Oliver, this isnt about global warming. You go off topic so do i.
Dr. Oliver Manuel Sr., Professor Emeritus of Chemistry and former chair of the UMR Chemistry Department, was arrested Tuesday, May 30 in his office at UMR for two felony counts of rape, four counts of sodomy, and one count of attempted sodomy. The crimes allegedly occurred from 1967 to 1990 at various locations in Phelps County. Some of the acts allegedly occurred on University property.

500 times over (which is how good space based power plants would need to do to just break even with ground based counterparts - let alone be cost effective).

Would you mind crunching the numbers including robotic self-assembly and nanotech please? Thanks.

Your conceptionism seems to be stuck in the past. Although you do use the 'metamaterials' buzzword so you do have the idea at least that things can and will change. They will be cheaper and better for the most part.

Or we can wait for the japan and california projects can provide some numbers.

For that you need another type of drive.

Correct.

With just over 3 and a half tonnes of fuel you could keep going for a decade.

With current tech. And factoring in the momentum gained from the pellets.
cont

We're already facing a multi trillion investment in converting from fossil/nuclear to alternative energy sources. If we do this with space based solar we'd be in the quadrillion range.

I dont think anyone would be considering putting ALL energy production in orbit -? Orbital stations can certainly augment future power production, and they can certainly serve double duty for interplanetary shuttle propulsion if this proves feasible. The wiki article mentions:

'A microwave beam could be used to send power to a rectenna"

-or even:

"A variation, developed by brothers James Benford and Gregory Benford [excellent scifi author], is to use thermal desorption of propellant trapped in the material of a very large microwave-sail. This produces a very high acceleration compared to microwave pushed sails alone."

-You know I bet if we looked we could find more recent proposals for interplanetary travel using these variations. You think?

Would you mind crunching the numbers including robotic self-assembly and nanotech please? Thanks.

Ah, sorry. I was under the impression we were talking about workable technology available now (i.e. something that could get us to Mars in teh next 2 decades) - not some pipe dream yet to be developed. If we're talking future developments then I'll drop out of this discussion...including stuff that may be developed in the futire one can argue anything.

They will be cheaper and better for the most part.

Sure, but having been a scientist I know how long it takes for stuff that is a lab prototype (like what is reported on physorg) to reach any kind of serious application - especially for space based ventures. We're talking 10-15 years minimum.

I dont think anyone would be considering putting ALL energy production in orbit -?

Well, the article also mentions the need for 65000GW of power for the 1000kg probe (that's roughly 5 times the world consumption today). This doesn't leave a lot of room for being optimistic about 'only putting a little bit in space'. We're talking serious power needs, here. And currently we aren't even able to put a 1GW reactor into orbit unless we do it over a few decades - let alone a good fraction of those 65TW. The numbers are, for the moment and the foreseeable future, just way too big to take this seriously.

You know I bet if we looked we could find more recent proposals for interplanetary travel using these variations. You think?

No.

For the simple reason: The numbers just don't add up when compared to simple chemical rockets (at least for the trip to Mars).

As I said: I love nifty tech. It piques a sense of aestehtics in me. But this...well...its just unworkable.

I find Zubrin's comment interesting in the face of a 2007 Reuters report that VASIMR had fired for 4 hours, not a few seconds. This was no doubt at less than today's 200kw output, but still....

http://www.reuter...p;rpc=22

What are the idiots doing?

Now this Chang, a scientist of Chinese origin will go back to China. Bu-bye American superiority, hello Chinese supremacy!

Stupid idiots attacking Ching, I mean Chang.

Perhaps it's destiny that China take supremacy and become a free and democratic country in the very near future.

"Now this Chang, a scientist of Chinese origin will go back to China. Bu-bye American superiority, hello Chinese supremacy!"

Hate to burst your bubble HTK, but Franklin Chang-Diaz was born in San Jose, Costa Rica (and has never lived in China!): http://en.wikiped...ang-Diaz

Personally, I don't understand why anyone would voluntarily live out their lives in the isolation and confinement required of manned space exploration.

However, if we're going to settle space, the logical place to start is the moon. And the logical method is to first send robitic systems capable of building a sustainable infrastructure, before the first human arrives.

With only a couple of seconds lag in comunications between the earth and moon, you could (on a relatively large scale) virtually colonize and develop it with remotes, safely operated by humans on Earth.

Paying for it though... there's the rub. The investment isn't likely to pay off in spades, now is it? How do you justify the expense?

Ah, sorry. I was under the impression we were talking about workable technology available now (i.e. something that could get us to Mars in teh next 2 decades)

Your vasimr vessel should be ready about the same time these are, with mods:
http://inhabitat....0-homes/

-I think teh vessel pictured at the beginning of teh article above probably represents teh result of -what- 30 years of R&D? Second gen solar power stations should be online by then, dont you think doctor?.

Well, the article also mentions the need for 65000GW of power for the 1000kg probe (that's roughly 5 times the world consumption today).

-For INTERSTELLAR travel. "...the VASIMR powered spacecraft heading to Mars." -is the topic. I must say for a Scientist you do seem to be very selective in your interpretationisms. Doctor.

For the simple reason: The numbers just don't add up when compared to simple chemical rockets (at least for the trip to Mars)

:) -Well- Heres a serious study already underway for launching spacecraft to orbit:

"Instead of explosive chemical reactions onboard a rocket, the new concept, called beamed thermal propulsion, involves propelling a rocket by shining laser light or microwaves at it from the ground. The technology would make possible a reusable single-stage rocket that has two to five times more payload space than conventional rockets, which would cut the cost of sending payloads into low-Earth orbit.

"NASA is now conducting a study to examine the possibility of using beamed energy propulsion for space launches. The study is expected to conclude by March 2011."

'But - this is not interplanetory excursionisms!' -says the good doctor. NASA says of this:

"But the technology could in the future be used to send missions to the Moon or to other planets..."

Link for the above;
http://www.space....ogy.html

"...laser relay stations in space. Powering missions over interplanetary distance would require even bigger lasers and telescopes, as well as different propulsion techniques using propellants easier to store than liquid hydrogen.

"Sending a spacecraft to a moon of Jupiter, for instance, would require a laser that gives billions of watts of power. "You'd have to have another couple generations of space-based telescopes to do something like that," Kare says."

'Billions' Hmmm lets see...

"PowerSat Corp. has filed a provisional patent for two technologies called BrightStar and Solar Power Orbital Transfer, that are expected make the transmission of space solar power more cost-effective by reducing the price for launch and operation of systems as large as 2,500 megawatts by about $1 billion."

Hardly. Current power plants do not pay for themselves 500 times over

Your numbers are shocking but unsubstantiated. Heres an orbital station in the works:

"Later hopes are to launch a $100 million, low-earth-orbit project by 2015 and then partner with a utility or government agency on a utility-scale project of 2.5 gigawatts, at a cost of $4-to-$5 billion, between 2019 and 2021. This is cheaper than nukes or clean coal."

"That makes the first of PowerSats breakthroughs of cost cutting technologies is called BrightStar important. It reduces the single big, array-carrying satellite into a cluster of hundreds of small satellites that work together with wireless electronic connectivity to broadcast a single beam to the earth receiving station, called a "rectenna."

-So many others. I enjoy fiddling with your myopia anitaliens. Its funny how you keep confusing interSTELLAR with interPLANETARY. Why is that?? Odd for a scientist to do that.

Benfords study:

"Only in the last few years have beam-riding sails fully emerged as a valuable addition to conventional solar sails. Robert Forwards prescient 1985 paper led to work by James Benford. and Richard Dickenson, in 1995. Under the leadership of Henry Harris and Neville Marzwell, JPL began experiments in beam-riding sails in 2000...

"One may ask why a simple chemical rocket kick-stage could not be used, rather than a beam. Although at a seeming disadvantage to sails, (which require no overhead mass for engines, nozzle or propellants) a comparison of the relative merits of both approaches must proceed using the equivalent Isp of the arrangement, as well as cost. Liquid boosters are expensive and have a lower payload mass ratio. High impulse solid rockets exceed the structural strength of a deployed sail with concentrated points of thrust. Microwave powers ~ kW/cm2 can give sails exhaust velocities at > 5 m/ssec, competitive with chemical rockets."
cont

http://www.physic...ails.pdf

"Laboratory sail flights can test acceleration & stability of carbon sails now."

-Beam stations in place and craft built within the same timeframe as chemical rocket programs. To mars. Beam stations can serve double-duty as domestic power stations, offsetting their cost and making them cheaper than chem missions.

Similar power stations can be placed in mars orbit for surface-to-orbit and return trips, reducing the need to produce fuel from martian materials.

-For INTERSTELLAR travel. "...the VASIMR powered spacecraft heading to Mars." -is the topic.

As noted before: we're upping the mass quite substantially if we want to send people to mars - something like three orders of magnitude. (And the interstellar probe was only to be accelerated for 900 hours by the laser). Feel free to do the math on that, but I'm not optimistic that the required power will be much less.

on a utility-scale project of 2.5 gigawatts, at a cost of $4-to-$5 billion, between 2019 and 2021. This is cheaper than nukes or clean coal

I hope it works. But if it's as 'cost reductive' as the space shuttle was supposed to be...remember it was supposed to get us a flight at 20 million per go because it was reusable? It cost nearly 450 million per flight when all was said and done. (and if you take the entire program cost then each launch was 1.5 billion dollars worth)

If they manage to make it as cheap as you say: more power to 'em.

As the cost of putting these gizmos into orbit and putting entire *powerstations* into Mars orbit is pretty steep. (and seeing that we don't even have prototypes of any of them yet)

I'm betting we'll do it the old fashioned way first. Let's first see if there is any point in going to Mars or not by sending two or three astronauts/comsmonauts/taikonauts there and getting them back.

The first one will be a race. I can't see lasers/powerstations and sails winning that one when everything has yet to be developed while the alternative is all ready to go. But we'll see.

Personally, I don't understand why anyone would voluntarily live out their lives in the isolation and confinement required of manned space exploration.

It takes a special kind of person to do that. One who realizes their life's dream. That's not for everyone. (I'd volunteer, though. Sounds like the adventure of a lifetime to me)

What engine has Zurbin ever done research on? What has he ever contributed to space propulsion design? Calling real research and tangible results a hoax disqualifies him from even commenting. If I ever heard of an annoying little hoax it is Zurbin.

If you investigate the VASIMR concept it is notably different from other ion thrusters in several ways, magnetic containment of the plasma being a significant and important difference. With regard to efficiency read AAIA 2011-1071 technical paper presented Jan 2011 which states: "Recent results at 200 kW coupled RF power have shown a thruster efficiency of 72% at a specific impulse of 5000 s and a thrust of 5.7 N." (I don't know where Zurbin got his 50% efficiency number but I suspect a body orifice.)
This engine has promise, it should be developed, & NASA has agreed to an ISS test. The power supply problem for an electric based rocket motor is solvable.

And as gswift mentioned these platforms will already be serving to transmit power to the surface. They will pay for themselves

The idea being looked at by DARPA isn't expected to be economical. It would be an emergency power source for front line troops at the tip of the spear, so they wouldn't need to take generators and fuel with them. They would use it for critical things like communication and field hospitals. The capacity would be relatively small, but could allow a much lighter assault force to do a lot more in less time. Reducing the need for logistics is always a key military advantage over an opponent.

The beamed power idea for reaching Mars is viable if you plan to use the system multiple times. You would use it to help get the mission started, when the craft is heavy with fuel. The craft would still be a conventional craft, but would receive a power boost when leaving Earth, when it needs the most help. You probably wouldn't need them at the Mars end of the trip

Every little bit of power you could provide externally would mean that much less fuel you would need to launch from Earth's surface into orbit. The benefit is exponential, as every kg at launch increases the cost exponentially. The cost savings gets really big when you start talking about large manned craft and repeated supply runs. For supply runs, the craft could take any amount of time to get moving, so the amount of power supplied could be very small. That way you could save all the on-board fuel for braking when you reach Mars.

If you plan the trip such that the craft heads towards the Sun first and then loops around towards Mars, then you could have solar power beaming stations in orbit around the Sun. You could also possibly use a solar sail near the sun. For a manned flight you wouldn't want to do that, but if we're going to put people on Mars then we're going to need lots of supply ships, even before they get there.

The benefit is exponential, as every kg at launch increases the cost exponentially.

Though to get the same amount of power out of a laser you have to put a lot more kg into space than if you just launch a fuel container. The cost for the laser solution will be much higher than for the conventional craft and i doubt it will ever pay for itself. Orbital installations DO have a limited lifetime.

But we'll pobably not launch a manned Mars mission directly fom earth. Likely we'll launch it into LEO in modules (much like with the ISS) and dock them. Then fuel the whole contraption up by launching a couple of ATVs with the fuel on board.

Possibly we could even send out an unmanned fuel carrying vehicle after the launch of the Mars mission to dock upon arrival on Mars. That way the initial mass of the large craft is lower.(And the fuel carrier could be very efficient because it has no other payload)

With only a couple of seconds lag in comunications between the earth and moon, you could (on a relatively large scale) virtually colonize and develop it with remotes, safely operated by humans on Earth.

Paying for it though... there's the rub. The investment isn't likely to pay off in spades, now is it? How do you justify the expense?

Mining helium-3 might well eventually justify the cost. We'll need the fusion plants first of course, and that's already at least 25yrs out. So I don't plan on seeing this before at least the 2nd half of the 21st century. Which is to say that I don't really plan on seeing this as all, unfortunately. Mortal coil and all that.

The idea being looked at by DARPA isn't expected to be economical. It would be an emergency power source for front line troops at the tip of the spear, so they wouldn't need to take generators and fuel with them.

Microwaves blanketing enemy forces might also provide suitable incapacitation? DARPA is not naive. If this is a viable weapon then they need to be the first to develop and deploy it.

California and japan probably have other intentions.

If you plan the trip such that the craft heads towards the Sun first and then loops around towards Mars, then you could have solar power beaming stations in orbit around the Sun.

Absolutely. The establishment of a fledgling system to provide power for transport and utility throughout the inner system, not unlike the alaska and siberian railways.

Rail transportation truly made the US a nation, just as it did russia. The inner system can be settled in the same manner.

Ad Astra Rocket Co. (VASIMR) posted this PDF after Zubrin's comments -

http://www.adastr...2011.pdf

Thanks for sharing the link to Ad Astra's response, DocM.