2008-12-05T16:12:03Z http://spacefaringamerica.net/comments/atom.aspx Quick Blogcast tag:spacefaringamerica.net,2008-06-27:1152243 Charles Jones 2008-10-06T19:23:30Z 2008-06-27T05:51:39Z tag:spacefaringamerica.net,2008-06-04:1096242 Kris Ringwood 2008-10-06T19:21:15Z 2008-06-04T14:28:27Z For SSTO, mass has to be got rid of/ reduced somehow,because our power plants are just not up to the job...unless we go to nuclear-thermal engines...!]]> tag:spacefaringamerica.net,2008-05-23:1068520 Mike Snead 2008-05-23T21:45:08Z 2008-05-23T21:45:08Z Here is the text from the blog: "If we are to rapidly proceed with building the infrastructure needed to support SBSP and other space industrial activities, it is very important that we avoid the trap of unnecessary requirements and unneeded technology insertion. These are the primary reasons why achievable two-stage aerospaceplanes have not been pursued in the last quarter century."

I wrote this from my experience looking back at government efforts to develop reusable space access systems over the last 25 years. For example, unnecessary requirements have shown up in the need for extremely rapid turn-around times of hours to a couple of days. In reality, a first-generation turn-around time of one-to-two-weeks with a fleet of 6-8 systems provides launch opportunities every 2-3 days. This would have been far more than adequate for U.S. space access needs over the last quarter century. Yet, the stipulation of rapid turn-around led to substantial requirements for new technology development that were unneeded for systems with 1-2 week turn-around times.

We have also seen comparable unneeded technology insertion demands. The airbreathing and single-stage requirement in the National Aerospace Plane program are two examples. More recently is the stated need for reusable rocket engines with 100 mission lives for a first generation reusable system. Modern large rocket engines can be replaced in less than 24 hours so engine swap-out time is not a real issue. Long engine mission lives with low flight rates drives up the engine production overhead costs as a percentage of the total engine price for the same reason that the Space Shuttle Main Engines were very costly. It is not an optimum from a systems perspective.

The trap that we need to avoid is letting the research community elbow their way to the front of the development program, by forcing the insertion of unneeded advanced technologies, or letting the operational community define specific system design requirements that can better be met through optimizing the overall system design.

I do not fault private industry for not pursuing fully-reusable space access systems because, as Hu Davis notes, the business risk is quite high. However, I do fault the prime aerospace contractors for not being more forthcoming with respect to informing the public as to what they have the technical ability to develop/build with respect to fully-reusable space access. Since the early 1970's, these companies have been making formal proposals and preparing, under contract, design studies that convey their belief in their ability to successfully develop and produce fully-reusable, two-stage, space access systems.  My expectation is that had their confidence in their abilities been conveyed to the public, we would not be facing the crisis in American space access that we have today. 

Mike Snead]]> tag:spacefaringamerica.net,2008-05-23:1067870 Hu Davis http://starbooster.com 2008-05-23T15:39:22Z 2008-05-23T15:39:22Z
I believe it is a very deliberate business choice - why take the chance that "build it and they will come" will increase the market and, even if it does, they will have to fly far more often at much greater risk, with no more in net proceeds.

How do we beat this attitude is more challenging than design of the "best" vehicle.]]> tag:spacefaringamerica.net,2008-05-20:1060595 terrence thompson 2008-05-20T21:15:07Z 2008-05-20T21:15:07Z Only those who will not see can still argue for non renewable energy sources.
A commitment to solar energy from space would promote national pride jobs and advances in technology as yet undreamed of.]]> tag:spacefaringamerica.net,2008-04-12:964860 Mike Snead 2008-04-12T13:34:30Z 2008-04-12T13:34:30Z
Thank you for your comments.

In my view the central issue with respect to the need to begin to develop SSP systems is the accelerating depletion of proven reserves of current non-renewable hydrocarbon fuels, growing local resistance to the exploration and recovery of new non-renewable hydrocarbons, an increasing world per capita use of energy, a growing world population, and growing political and scientific sensitivity to anthropogenic-caused environmental changes (not specifically global warming).  By 2050 the world will need to be well on the way to replacing current sources of hydrocarbon fuels with alternatives that do not force a diminishing U.S. standard of living or constraints on desired increases in the world standard of living.

Fundamental to this transformation is a plan that builds on known technologies.  While the on-going significant R&D in new energy sources, energy conversion methods, energy storage methods, etc. will create new transformation opportunities, a starting plan for the needed orderly but aggressive transformation must be defined and initiated.  This plan can be updated as these new options reach the point of maturity when engineering development can begin.

While we need a diversified portfolio of energy sources, it is clear that the world is moving towards an increased use of electricity, in part to support an increasing world standard of living and as a replacement for hydrocarbon fuels.  This requires baseload and on-command electrical power generation that meshes with demand.  Nuclear and SSP are the two primary candidates for new baseload generation while large-scale energy storage, wind, terrestrial solar, waste stream fuels, SSP-derived hydrogen, and other biofuels may be suitable for peak power generation and necessary fuels for long-distance transportation.

Mike Snead]]> tag:spacefaringamerica.net,2008-04-11:963283 MEL AVERNER 2008-04-12T12:51:05Z 2008-04-11T18:39:17Z tag:spacefaringamerica.net,2008-04-03:942724 Mike Snead 2008-04-03T21:49:33Z 2008-04-03T21:49:33Z
There are many possible approaches to achieving a fully-reusable space access system.  The problem is that is takes considerable engineering resources to transition ideas into a viable concept with defined and available technologies and critical subsystems.

Mike Snead]]> tag:spacefaringamerica.net,2008-04-03:942705 Mike Snead 2008-04-03T21:43:25Z 2008-04-03T21:40:47Z
Thank you for commenting on the Space Review article.  I would like to comment on the second point that you raised.

Adrian: "I also believe that the whole "airplane-like" efficiency thing needs to be wrestled down to reality. I don't think it's a good analogy primarily because the volume of air traffic is probably always going to be much higher than even a robust space-faring system, and always less technically challenging. It somehow implies that we could -- and need to have -- orbital craft that could take off from any airport, willy-nilly, and do so on an hourly basis. There is no such need, nor will serious exploitation of Space even require it. A very robust and lower-cost collection of launch systems could sustain a large and viable space-faring effort even if the vehicles have to take off (and perhaps land at) from a limited number of dedicated launch sites."

Response: A true spacefaring nation requires the ability of its citizens to be able to access space safely and routinely.  We have two models of space transportation that can be pursued to achieve this goal.  The first is an extension of today's expendable or partially-expendable space access systems.  The second is an extension of current airplane operations.  The difference between these two is not the mode of propulsion, but the design, engineering, and operations model.  A comparison of the advances in safety, cost reduction, and operations since 1958, the start of both the jet age and the space age, are very telling.  Commercial aircraft operations have advanced significantly in all areas.  Space access has generally not advanced and, given current plans for the next generation of human space transportation being pursued by NASA, will not make any substantial improvement in safety, cost reduction, or operations for another generation.

Our need now is for a fully-reusable, two-stage space access system developed as an extension of airplane operations.  This means that the design and operation of these systems will come through the application of the aircraft-style system engineering processes that have proven to be very successful in developing increasingly better air transportation while incorporating new and improving technologies.  Achieving "airplane-like" efficiencies are a product of the successful application of these engineering processes.  Such a capability can be achieved in ten years.

Mike Snead]]> tag:spacefaringamerica.net,2008-04-03:941658 Adrian Reilly http://www.geocities.com/rreilly656 2008-04-03T21:44:39Z 2008-04-03T12:48:14Z
Why not an interim ram-jet-based system? A rocket sled could build up enough speed for ramjets to start up, and, realistically, a ramjet flyback booster could get to MAC 4 or so before separation. The idea is as old as the Space Age (Wily Ley), and doesn't present the technical barriers that scramjets do. Also, the resulting speed and altitude should be enough to achieve orbit with a single, remaining, reusable rocket-powered orbiter stage. The flyback booster in this concept would be more compact than a rocket-based one, especially if the initial rocket phase comes from a sled that never leaves the ground.

The other option that crops up is the Air-Turbo Ramjet for fly-back boosters. Any merit to the claims that ATRs can achieve low hypersonic speeds from a dead start on the ground?

Please correct me if my assumptions are simplistic.]]>