Monday, January 31, 2011

Mea culpa

For not paying more attention to these sooner.

Is IEC fusion that close?  Somebody seems to think so.

Combinations, Part 2

I first wrote about Parkin's microwave thruster here.  To recap briefly, it uses microwave energy to heat the reaction mass which provides thrust to send the rocket into orbit.  It differs from chemical rockets in that it doesn't use combustion to achieve thrust.  The necessary energy will come from a base station on the ground and this will provide the energy to get to orbit.

My proposed combination follows:   But what if you could place the base station in one of JP Aerospaces' proposed Dark Sky Stations?  It would provide energy to lift the airship nearly vertical until it is out of the atmosphere.  Then, without the friction caused by the massive size of the airship, it could then fire an onboard rocket and achieve orbital speed before it re enters the atmosphere.

In practice, the Airship To Orbit (ATO) vehicle will leave the Dark Sky Station (DSS) as currently envisioned.  But it would have to stay within reach of the energy source of the DSS in order for this to work.

Once it reaches it's limit of acceleration and altitude, the DSS then fires its beam and this will give thrust to the ATO causing it to rise nearly vertically.  This is the trajectory proposed by Parkin and for the same reason.  But Parkin wants out of the atmosphere because he wants to impart massive forward acceleration in order to get to orbital velocity within 200 miles of the range of the microwave source.  But to avoid massive g forces in that trajectory, just raise the airship even higher in order to get potential energy that can be translated into forward speed to orbit.  While falling back to earth, apply rocket power to counter the gravity of the earth and using that energy in the fall combined with the onboard rocket's energy will hopefully impart sufficient energy to get to orbit.

Parkin proposed a range of 200 miles for his microwave energy source.  If you could add that much altitude to the ATO, it would have the 200 miles plus the 30 miles or so of the DSS giving a final altitude of 230 or so miles before it started falling back.  If possible, forward thrust could also be supplied as in the Parkin model trajectory, but without the significant g forces.  The goal is to use this for manned launches.  Parkins model trajectory has too much g forces for humans to be onboard.  This proposition would use the same conceptual trajectory, but in a novel way in order to achieve orbital velocities without excessive g forces.

Saturday, January 29, 2011

How did I miss this one?

Because I've been spending a lot of my time doing other things, like promoting this blog.  Guess what?  That's how you miss stories like this.  It is the follow up to the post on Mining Asteroids is Hard.  Colin Doughan's got an interview with someone who may be trying it soon.

Friday, January 28, 2011

An observation

In an earlier post, the feasibility of mining asteroids was discussed.  It occurred to me that all discussion seems to point to the assumption that every mission has to originate from Earth and every destination has to be an immediate return mission.  But what if people could stay in space for years at a time?  What if you could mine an asteroid for awhile then jump to the next one when it made sense to do so?

A moon base could serve as a jump off point for mining missions.  Or it could serve as a jump off point to create more jumping off points that could eventually support mining missions on a continual basis.  In order to reach this goal, you have to start somewhere.  The most logical point is a moon base which can sustain a long term presence in space.  The main purpose of the moon base would be to launch missions from the moon, as opposed to launching them from the Earth.  I suspect that I have written this before, but the logic of it is inescapable.  The main hurdle of space commercialization is launch cost.  Those costs can be reduced to manageable proportions if the launches were conducted from the moon.

Update:  moments later

It may that the cost of getting stuff into orbit is too high, yet there was a launch system contemplated briefly by NASA in the early sixties that would have been able to put 550 tons into LEO.  This system, called a Sea Dragon, would entail a launch from the open ocean.  The rocket would be towed from the mainland, then rotated into position where it would be launched.  The Sea Dragon concept was proved, so it wasn't some way out idea.  Launch costs were estimated as 1/4 of the costs of the eventually operational Saturn V rocket that took astronauts to the moon.

The key to me is not the launch costs.  It is the mass of what could be put up there at one time.  You have to consider that 550 tons is an awful lot of stuff on one launch.  Now if you were to put enough stuff up into orbit, you can start doing things.  One example is that you could launch multiple missions on just one launch.  For instance, one estimate for the amount of mass needed for a Mars mission is 170 tons.  Imagine putting up materials for 3 missions from just one launch.  Or one mission to do 3 times as much stuff.   On your mission to Mars, you could set up the capability to do some mining, or prospecting for mining.  Try to imagine the reaction if the astronauts upon return had marketable amounts of imports from the journey.

Thursday, January 27, 2011

Enthusiasm meets reality

Sometimes your enthusiasm can cause you to get ahead of yourself. Speaking for myself, I may need a little skepticism about JP Aerospace. Yet, I don't want to pour a lot of cold water on the idea either. If you look at the way he is going about it, he appears to be answering some of the points that some skeptics bring up.

Rather than to go into all of that, I added a few more links this morning to the lists of interesting reading. One of those was called: "The Challenge of Cheap Orbital Access". By the way, one of the contributors was Dr. David Livingston, who does the "Space Show". That link went up too, and for good measure, I bought a bumper sticker to promote the program and mentioned it on my Facebook site.

Well, anyway, a healthy skepticism is called for. For example, yesterday I listened to a mp3 file that you can download from the website. This is the third or fourth one of these that I've done this. This program was recorded the day or two before election day and it covered some ground which led me to the site mentioned above.

There was some discussion of one of the problems of getting an airship to orbit. One such problem is air drag.

There was an email to the show which was read on the air and stated
that even at 250 statute miles, the ISS experiences friction which slows
it down. Given enough time, the ISS would fall out of orbit. It needs to be
reboosted from time to time and this actually requires expenditures of
money to accomplish this. The idea of using a balloon to get to orbit seen
within this context does seem improbable. But before dissmissing the idea
completely, I would like to see how that problem gets addressed. Because
the airship stops being an airship whenever it can't use the air inside it for
flotation nor aerodynamic lift. Once those two things are no longer possible,
the aircraft becomes a spacecraft. How does it make that transition?

That's the 64k question.

By the way, the ragged format of this post was due to the fact that I took notes on a text file and tried to repost without having to rewrite the whole thing.  The results are as we see, a ragged looking post.  But I am not in the mood to rewrite the whole thing in order to make it look better.  Sorry.

Thursday, January 20, 2011

Mining Asteroids Too Hard?

In a post that I'm studying a bit, I have come to a few preliminary conclusions that it is too hard now, but perhaps not later.  Launch costs have to be reduced eventually, or we all stay grounded indefinitely until it does.

He uses a mission cost of 600 million dollars in his example.  But he doesn't break it down into its various components.  How much for the mining equipment and launch costs separately?  What can realistically be reduced?  What can be improved upon?  The yields for the mission seem low.  You don't want to go all the way out to an asteroid and only mine 43 million dollars worth of the stuff.  You have to have higher yields or it doesn't make sense.  That would be true even if you got launch costs way down.

It may be hard to mine asteroids profitably at these assumptions.  Maybe the assumptions are all realistic.  If so, even in the best cases, and with launch costs much reduced, we still may not see much mining of asteroids.

The yield is too low.  Can you do any mission like this for 43 million?  Even with lower launch costs?  I was thinking of a yield of half a billion and launch costs much lower.  That would leave plenty of room for profit.

Catepillar drives

Remember the movie "The Hunt for Red October"?   It was about a new submarine with an advanced propulsion system that was so quiet, it couldn't be detected.  This made it a great military threat, so the good guys, meaning US, had to figure out a way to deal with the threat.

Well, I was perusing JP Aerospace's blog and they appear to be working on an MHD, which means a magnetohydrodynamic drive or catepillar.  This is going to be their rocket motor that takes them to space. Well, I am only guessing that this is the case.  What I read is a number of posts on the subject of testing an MHD.  The name seemed to ring a bell, so I did a bit of digging around and found this site that explains what it is.

I don't know how this will turn out, but it should be interesting.

Wednesday, January 19, 2011

Carbon nanotubes

Development of carbon nanotubes is often linked to the construction of a space elevator.  But you need tons of the stuff for a space elevator.  Now if you were to use this material in order to construct a really strong airship, you just might have something.  In his Space Show broadcast in 2008, which I have referenced here, John Powell of JP Aerospace says he isn't counting on the development of carbon nanotubes for his airships.  

It would appear to me that he is probably correct.  His airships just won't need much material in terms of weight. Graphene can be used to strengthen plastics.  If you have enough graphene in plastic, you have a really strong lightweight material that just might make it to space.

I will be writing more about JP Aerospace in the future.

Update: 1/19/11, approx 11:45am cst

I got the book referenced above.  It has a DVD which I've played, or played most of it.  Haven't had time to read the book yet.   Just to give an idea of the kind of strength in the materials mentioned above, check out this quote (if you haven't done that already):

"It would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap."

Strong stuff.

Monday, January 17, 2011

Rocket Science for Dummies

Sounds kinda funny, yes?  They always say "it doesn't take a rocket scientist to figure it out."  Rocket science for dummies sounds funny.  I thought it may make a good joke.  Anyway, I've been fooling around with the rocket equation and I figure I could use one of those books.  It might be easier just to defer to a rocket scientist after all and not try to figure certain things out.

I've been trying to figure out how an airship can get to orbit.  Even though I don't understand it, just fooling around with these equations and numbers gives you some ideas.  I'm too old to go back to school and learn how to be a rocket scientist though.

Fuel Cells

When looking at alternative fuels, such as hydrogen fuel cells, there exists the challenge of how to do it so as to be competitive with existing technologies.  The trick is to gain the advantages while overcoming the disadvantages in order to reach the goal of a competitive new transportation technology.

Hydrogen is the simplest, commonest element in existence.  That's good and that's bad.  The good thing is that it can be clean and plentiful.  The bad thing is that it takes a lot of volume to contain any of the stuff.  The result is that you have to compress it or cryogenically store it if you want to use it.  Whatever your gain was gets lost in transport or storage of the gas.  How to overcome the disadvantage and gain the advantage sought for?

There was this demonstration program called the NECAR which demonstrated one way of overcoming the storage problem.  The solution was to not store hydrogen at all, but to produce it on demand.  This method used a reforming technique to produce the hydrogen.  There may be a better way.  Here's another way to produce hydrogen from methanol:

NPO19948 methanol hydrolysis.pdf

 This is from a NASA produced pdf which I downloaded several years ago.  It may already be in commercial use, but I am not sure about that.  What its capabilities are, I don't know.  Some questions that I would have, if I could get it, would be this:  could this thing be an improvement upon the reformer method used on the NECAR?  In other words, could you put one of these on a car and drive it across country?  How would it perform?  Would it be economical?  Has anybody tried it?

In an attempt to answer this question, I didn't get very far when I went to the NREL site.  But one thing I did notice is that this method wasn't tested.  Why not?  I don't know.  It may have been tested in terms of producing hydrogen to be distributed to FCV's, but not actually on an FCV itself.  By putting one of these on an FCV, you can get around the problem of hydrogen storage.  This could solve the problem, but at what cost?  Could it be done and if so, what would it cost?  Would it be economical?  The NREL doesn't mention that as far as I can tell.

I noticed on the Ballard Fuel Cell Site awhile back that they may use this technique of extracting hydrogen from methanol by hydrolysis, but my casual perusal this time didn't yield quick results.  So, I don't know as of this writing whether or not they use this.

A possible experiment could be to see if you could power a Chevy Volt with a Ballard Fuel Cell combined with a methanol hydrolyzer (assuming one exists) that would reproduce the NECAR results.  It would be interesting to see if the results would be better or not.

Update:  1/17/11, approx 1:00pm cst

This 2006 article in Technology review shows the problem with direct methanol fuel cells.  The problem is the cost of the catalysts such as platinum and ruthenium.  These catalysts may be available in large quantities from asteroids or perhaps the Moon.

The above mentioned hydrolysis is a slightly different process, yet the result is pretty much the same as direct methanol fuel cells.

At any rate, you would only have to fill up at the pump as you would now.  Instead of gasoline, you would fill up with methanol instead.

One advantage of fuel cells is that they are much more efficient than an internal combustion engine.  It would require less fuel to achieve the same result.

Saturday, January 15, 2011

Some questions on the Space Show, Floating to Space

The Space Show callers had a few technical questions which I thought I'd
comment upon briefly. One caller asked about energy source and John's
answer was a solar electric combination- most likely using batteries.

My comment is that it may not be the best idea because batteries are
quite heavy. That adds a weight penalty that you may want to avoid in
attempting to get to space.

The second question was about shock waves as you approach supersonic
speeds at high altitudes. John's answer was to manage that problem
at altitudes. The higher the altitude, the less the problem was. He
said the following altitudes were targeted to attain the velocities listed:

Below 200k ft. subsonic: begin to lose buoyancy, begin aerodynamic lift
240-260k 300 mph up to supersonic
above 240 k supersonic, not clear here; assume below 240k ft is subsonic
300 k supersonic; above 300k is supersonic to hypersonic, I gather
316 k hypersonic At this altitude, you are approaching space itself.

The third question was the most challenging. The questioner, named
Charles, asked how do you impart the necessary energy with batteries.
The most powerful batteries known could not come close to the
energy requirement of getting to space. He observed that the
energy requirement is 33 megajoules per kg mass no matter how you
do it. A battery cannot deliver that kind of power,he says. He
was also doubtful about solar too.

I ran some numbers on that. According to the wikipedia, there
are about 10 kilowatt hours per kilogram according to the number
that Charles gave. A kilowatt hour is over 3 million joules.
Therefore 10 kilowatt hours per kilogram satisfies Charles claim.

Incidentally, this is not the answer that John gave. It is the
one I looked up myself. Not that the source that I've given is
accurate or correct. If what I cite is correct, then the power
requirements seem daunting. But not necessarily impossible.

I don't know the mass of his airship, but it is quite large.
If the weight is 100 times his Ascender airship that he described,
it would only weigh 600 lbs times a hundred, or 60,000 pounds.

That figures to 272,000 kilowatt hours.
Or 2.84 megawatt continuous power over 4 days that he anticipates
that it will take to get to orbital speed.

Charles may be right in that it may take more than batteries
to do the job, but that kinda what I figured in the first place.

Update: Sun. 1/16/11, approx 9:15 am cst

In case the above seems rather unfavorable to this concept, I should note that John
mentioned that he has turned down investment offers in his enterprise.  The reason,
from what I gather, is that he would prefer to keep independent.  Any investors would
want return on their money according to some timetable which may not be feasible.  I
would only add that if a timetable could be plausible to make this concept's feasibility into
a more highly probable favorable outcome, that he may want to reconsider any new
investment offers that may come along.  That's because trying to do this solo may take
longer than he has left in terms of his own lifespan.  He has been at this for over 20 years,
according to the show.  So, he may want to reconsider since he won't live forever.

Thursday, January 13, 2011

A thought experiment on rockoons

Well, not exactly a rockoon.  A rockoon is a rocket launched from a balloon suspended platform.  This would be a twist on the concept.  Let's make the balloon into a rocket too.  The "balloon" isn't a balloon exactly, though.  It is an airship.

In an earlier post back in October, I came across Parkins' Microwave Thruster concept.  This concept employs microwaves to heat the reaction mass of hydrogen in order to provide thrust.  Now, what if you can employ this concept on airships?  Zap it with energy from the Dark Sky Station and heat up a reaction mass in order to provide thrust.  Parkin's device is efficient and could provide plenty of thrust.  The problem is getting something up there that could provide lots of energy so that the airship could have sufficient thrust to get to orbit.

The Dark Sky Station is huge.  I am supposing that the energy source can come from there.  It would have a short range available to it in order to give the Orbital Ascender sufficient thrust.  Parkins suggests an upwards trajectory above the atmosphere, then a short burst to get it up to orbital speed.   The idea I had was to use the ion engines to supply forward speed and the electrodynamic tethers to maintain altitude in combination with this concept here to provide the necessary thrust to reach orbital velocity.  Short bursts from the Dark Sky Station would be applied on each orbit to give additional thrust and to keep G forces from being too extreme.  The ion engines would supply thrust forward to maintain or increase speed while circling the earth on each revolution.

I wonder, could a concept like this work?

Update:  1/13/11, approx 11am cst

I am still thinking about this concept.  Here's another thought:  raise the Ascender to 200,000 feet using lighter than air flotation.  Once you've gotten that far, use Parkin's idea to raise it the rest of this distance into space.  But instead of giving forward speed, just increase altitude.  Once you've attained the altitude of 200 miles, release a conventional rocket which will be able to attain orbital speed before it can reenter the atmosphere.

You could also use an electrodynamic tether to aid in increasing altitude and maintaining it for launching the rockoon.

Wednesday, January 12, 2011

Can spacecraft move due to magnetism?

I used the above title of this blog post in a google search and came up with this link.

The reason this interests me is that JP Aerospace has this idea of using airships to orbit.  I was wondering if such a large airship as they are planning will give enough lift to get the airship above the atmosphere by using this technique.

I am not aware that such a technique is envisioned in their plans, only that some folks are doubtful of the airships capability of getting into orbit.  The one problem such an airship could have is friction.  Once it gets up enough speed, it will begin experiencing friction and that could jeapordize the airship.

I did note that the airship will be aerodynamic, which means that they anticipate enough forward speed to give it some lift.  But that alone won't be sufficient to get above the atmosphere.  Once the lift is gone, altitude gain will have to come in some other fashion.  Yet there could still be enough atmosphere left to cause friction which could be a problem.

Now if the airship had enough lift from a magnetic field so that it could rise above the atmosphere, it could have a better opportunity of reaching space before burning up from friction.

Update: 1/12/11, approx 3:20pm cst

It appears that an electrodynamic tether of the type was being considered by the Russians for boosting their Mir space station to a higher orbit.  It consisted of a 330 lb assembly with a 3 mile aluminum wire tether.  Source Van Pelt:  Space Tethers and Space Elevators p. 132.  Power requirement were a few kilowatts, not too much for a solar power array.

Thursday, January 6, 2011

Robert Zubrin on Energy Independence

This isn't new, I know. It may be useful to consider it though, as part of a comprehensive plan for energy independence. It would be especially useful in the case for methanol, which can be produced by a gas to liquid process from natural gas. Natural gas deposits have been found in recent years, which if converted to methanol, would be a big help with the oil import "addiction".

Tuesday, January 4, 2011


I thought for sure that I'd written about this before on this very blog, but the Google search of this blog produced no hit for Nerva.   My page titled "Little Search Engine that Could" yielded a bunch of hits.  That plethora of hits may not include this page , but I know I have seen it before.

What drives my interest here is the possibility of using this technology with Ad Astra's VASIMR.  The thought of getting that much nuke power into space seemed daunting, yet this was within reach back in the Apollo days.  It got cancelled just before it could go operational.  Therefore, this is definitely not far-fetched.  It is feasible and nearly operational decades ago.  That should remain the case today.

There are questions, of course.  Could this be modified to work with VASIMR?  And should it be modified?  After all, VASIMR did not exist 40 years ago. Would this technology mated with VASIMR produce an even better propulsion system?  The possibility of sending a crew to Mars in 39 days with this does not seem so implausible after all.

Note:  I include this link in French because it appears to be discussing the Nerva program.  I don't know French, but maybe I can some of this translated.

Update:  Here it is, translated by a software add-on to Firefox

are purchases understand a on probation free membership in the club of pounds of the editor, in whom you can choose among more than a million works, without expenses. The book consists of articles Wikipedia on: Thermal Nuclear Propulsion, Orion plan, Nerva, Blown Nuclear Propulsion, Propulsion by Fragments of Fission, Radioisotopic Propulsion, Daedalus plan, collector Bussard, Longshot plan. Not illustrated. Online free updatings. Extract: Thermal or nucléo-thermal nuclear propulsion is a mode of propulsion of the missiles which uses a nuclear reactor to heat a propelling fluid. This one, as in the case of a motor - classical missile, is evicted via a blast pipe to provide the increase which projects the missile. This type of propulsion allows to attain in theory distinctly more well brought up speed of ejection of gas and therefore better output than chemical propulsion used on the actual pitchers. Different architectures were studied since the beginning of the space epoch of the simple solid heart (similar to that of a nuclear power station) up to more complex but more efficient concepts such as the gaseous hearts.
Although an archetype is tested on the soil by the United States (motor NERVA), any using missile this type of propulsion has still never flown. Important researches are still necessary between others to diminish the report weight / increase. If it is kept, nuclear propulsion will have to face up a party of the public opinion basically hostile to any launching of nuclear devices. Today, the appeal in nuclear propulsion is recalled only as part of program Constellation, for hypothetical lived missions towards march, in distant expiry date (after 2037). Schema of a thermal nuclear motor In a system of thermal or nucléo-thermal nuclear propulsion, a propelling fluid, in general some hydrogen, is heated

Comment:  Not much about Nerva.

Update: 1/4/2011: aprox 11:15 am cst

Upon "further review", it appears that using a Nerva system and VASIMR system together is not necessarily convenient.  Nerva heated the propellant directly.  Why reconfigure it to produce electricity for VASIMR so that it can heat propellant indirectly?  It is wasted energy, and adds complexity.   Hmm.

Yet the Nerva system shows ( I think) that you can get the energy equivalent up to VASIMR's needs.  If there is an advantage here, it could be two fold: 1) a longer lasting system in the VASIMR as opposed to the Nerva and 2) less propellant used than the Nerva.  The savings in propellant need to overcome the increase in hardware and complexity in order to make it worthwhile.

Update 1/5/2011: approx 7:20 am cst

I want to get into the habit of assessing odds of certain events.  I've written a bit about VASIMR lately.  In terms of getting to Mars, I want to predict that this is not likely with the VASIMR.  I see it as more of a space tug technology.

Monday, January 3, 2011

Ad Astra Rocket Company

I spent a little time reading their website.  In case you are not familiar with this company, they are the ones who are developing the VASIMR propulsion system which will roll out on the ISS in 2014.  As usual, I may have been a bit hasty in my enthusiasm for space and included this in technology that is "just around the corner".  There are a few more technological hurdles to pass for this technology.  This quote here from Aviation Week, June 18, 2010 by Mark Carreau, was interesting to me because I think there may be a way to use the heat which is causing a problem:

Meanwhile, Vasimr’s success depends on overcoming other technical hurdles. Though the high-temperature plasma is constrained by magnetic field lines, some of the ultra-hot particles reach the inner walls of the engine.

In some of my reading last night, it looks like they are trying to find a way to cool it down.  I wonder if using a Stirling type device to generate electricity could be useful in this instance?  That would turn waste heat into an energy source which could power an active cooling system.  The VASIMR system requires a lot of energy, yet the energy gets lost as waste heat and its a problem.  If the waste heat can be recycled back into the system, would it not be more efficient?  Could that waste heat become a resource?  Just a thought.

By the way, I included a link to Ad Astra in my sidebar on the left.  Lots of interesting reading there.

Saturday, January 1, 2011

More on the Space Cannon

I could have been a bit hasty in saying that the Space Cannon concept is around the corner.  So, I spent some time today on the subject to see if anything there looks different this time around.

Here's a wikepedia entry on the man, John Hunter, who presented the video which I had linked to in the earlier post.  There are a few more links about the man from the wikipedia entry to check out, but information is sketchy.

This presentation is a little over a year old, so I am looking for signs of progress since that time.  He is on a 8 year time table according to the presentation.  So, it has been a year.  What has been done in the past year?  It's a bit hard to tell from where I am standing.  This comment is the most recent I can find.  It doesn't tell anything.  In fact, it isn't even relevant.

In his presentation, he admits that he is not a rocket scientist, but his concept will require one.  That's because the projectile that he plans to put into orbit with his space gun will need a rocket to get into orbit.  Also, he says in his presentation that he will meet some venture capitalists for funding.  I wonder how that went.

If, by any chance, that things went well, sometime in the next few years, there could be an IPO for his company.  A lot will have to happen before that can occur, however.  For one thing, he will need a customer.  Most likely, even at this point, his only customer is likely to be NASA.  Maybe some private companies can use this service,  however.  I am not well versed on the subject enough to make a guess on the probability of that.  If he can secure one big customer, like NASA, he could be on his way.

So, in the end, his problem is that he could have a technology that needs a customer.  Without a mission from NASA or a private customer with a need for his service, it won't matter if his idea will work or not.

Now for a dash of speculation.  What if you were to employ this concept on the Moon?  It would be a way to avoid using much propellant.  And it would be better than a mass driver.  That, according to Hunter.  The trick would be in getting the gun up there.  But a lunar version of a gun like this wouldn't have to be nearly as powerful.

If a version of this gun were to be used to move lunar volatiles to the equatorial region so that a Moonstalk could be built, that would be interesting, yes?

Vasimr to Mars?

Here's a YouTube video on the VASIMR.  More about the VASIMR in a September article in The Space Review written up by Jeff Foust here.  The Space Review article is about proposals to use VASIMR for a Mars mission.

It looks like Zubrin is in a big hurry to go to Mars.  A Mars mission looks too ambitious to me.  Put up the lunar infrastructure first.  That is a better use of the VASIMR technology.  A 500 meg nuke reactor is mighty big.  Too much to get up there and to power that thing.   Zubrin is right about that.  But he may be wrong to try to push for a Mars mission too soon.

Just my two cents.

Interesting comments in that article as well.  All well worth a read.

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