An excellent essay. Let us watch and hold NASA accountable to spend their not insignificant funds that will become available to support technology development, technology transition activities, mission development, mission execution and commercial space operations as Constellation and the Shuttle programs wind down over this next year.

I am not an expert on the magnetosphere, but from the information available I do not see much thinning at the poles. It appears to be thinnest at the Sun-side. See http://en.wikipedia.org/wiki/Magnetosphere. Remember that the pulsed nuclear system does not have a very directional exhaust plume, it tends to blow all over the place.

I certainly applaud your enthusiasm, my twenty some years of experience in advanced space system development has lead me to believe that even some technically feasible solutions will not see the light of day due to politics, public opinion or economics.

The man on the Moon was a dream for many years. Polar orbit? Why polar? You loose nearly a kft/second going polar. If you need to be free of the Magnetosphere one of the L points makes a lot of sense.

Sad eh? All the lost opportunities to learn lost with the decision to develop the Shuttle and drop all else. The post Apollo activities had included the variable g facility that would have given us the data we need to determine if, or how detrimental the long term effects of Lunar, Martian, Titanian(?) gravities would be. Or if a human could adapt to a daily routine that could be 8 - 10 hours of weightlessness followed by evening, sleeping and morning activities at some g. How much g and time is needed? How hard would it be to transition back and forth? How interesting the 1970's and 1980's could have been.

At least he toilets would have worked.

Sure, nuclear pulsed plasma propulsion combines both high thrust AND high Isp. I would make the solar system accessible to manned travel, prospecting in the asteroids etc. etc.

There are a number of concepts that have been explored since Orion, check out http://en.wikipedia.org/wiki/Mini-Mag_Orion. Considering the size of the detonations, they should be clean, relatively speaking anyway. I have no information on the possible contamination and the effects of the contamination by the magnetosphere. Recall that the original Orion was an Air Force battle station intended to be launched from the ground! What a sight. Those were the days, when fear of the Soviets outweighed the fear of radioactive fallout from such operations.

I have no idea if nuclear materials are minable on the Moon or asteroids. One could launch the materials from Earth if there was real value. Highly enriched uranium is not particularly radioactive, it is just a toxic heavy metal like lead. Earth-Moon L points would certainly be promising basing locations for this class of interplanetary vehicles.

One could dream.

I would certainly agree that access to GEO has very significant commercial value. GEO is where the money is.

Manned presence (using the term generically) is not required for a vast majority of feasible currently available missions in GEO or cis GEO space as robotics solutions are up to the task of providing propulsion, attitude control, and perhaps the ability to free stuck mechanisms. With additional design features on the communication birds, supplying power or propellant, or replacing external components would be other possible services.

I would like to point out that GEO is a propulsively difficult orbit. To get there from a 200 km 28.5º inclined circular orbit using a Hohmann transfer requires 4,303 m/s. Assuming LOX/H2 propulsion (~450 sec) will require a mass ratio of 2.65. To initiate a return will require an additional 1,500 m/s which if accomplished using storable propellants (~320 sec) will add an additional returned mass ratio of 1.6.

To get to L1 using a direct Hohmann transfer will require from 3,996 m/s for a mass fraction of 2.48. Using the Moon rotating gravity well could nearly eliminate the 885 m/s insertion maneuver propulsion requirements reducing the mass fraction to 2.02, assuming you have some time. Returning to Earth would require 881 m/s for a direct transfer on "tens of m/s" if time for if or more loops around the Moon is acceptable.

I do not believe that the issue is due to advanced or advancing technology. The deep water cutters, NPOSS or the AF tankers were intended to contain anything but proven technology and components. The common thread appears to be the contracting for and integration of large complex systems that as a rule must interface with and have numerous requirements imposed by external developmental and operational environments.

My personal apologies to Elon Musk for butchering his name.

From the 9/8/08 Space Review, Edmon Musk was quoted in Jeff Foust's article *Looking (Far) Ahead* saying "The development cost of the Falcon 9 Heavy H “is hard to say” at this stage, he said, but thought it was on the order of $1–2 billion..." I would guess that a majority of this cost was the engine and avionics development, the airframe, being welded aluminum tanks is pretty basic and understood.

This is a two stage vehicle; thermally the first stage could be recovered using these materials, assuming that the sea water impact and immersion still allowed an economical refurbishment. More of a salvageable architecture than a reusable one. The upper stage would have to be very different to be recovered with either a kmile cross range capability or the ability to operate on orbit for 24 hours to be recovered back at the launch site in addition to the thermal protection, control and terminal deceleration systems. All of this would add significant cost, loss of performance and operational flexibility due to increased complexity and reliability requirements, inert weight increases, and sensitivity to weather and sea state. One would have to procure and maintain a recovery ship (rent from NASA?) and a refurbishment facility.

The cost benefits of reusability get more complicated the more one investigates the issues. Even expendable systems are manufactured on a schedule that could barely be described as an assembly line. How does one develop a product line where a full production run is three or four vehicles? How does one deal with unplanned losses? We have seen NASA grappling with these and many other issues with the Shuttle system. Even NASA admits that they are recovering the SRBs for safety and reliability issues, and is not really economical.