Certainly we could accomplish a lot by 2069.  However, it seems to me that at this point it is inevitable that the space program is going to take a giant step backwards. Constellation program is a giant Apollo Redux effort which may take us back to the Moon in 17 years after its initiation.  It only took us eight years to go to the moon with all of the technology push involved in Saturn/Apollo in the 1960s.  So much of the Constellation/Orion is off the shelf technology and it takes 17 years!  After the Shuttle is retired it will still take until 2015 to just get Orion going to let us get to the International Space Station.

 
Every president since Reagan has failed to support a strong space program.  Ill give Reagan credit because he started the space station, stood by the shuttle after the Challenger explosion, and pushed the NASP effort.  The failure of Clinton to realize the Shuttle time was coming to an end and start a serious replacement effort has been our down fall.  Even the X-33 technology demonstrator was cancelled over very minor budget issues when it could have test flown two key technologies: the aerospike engine and a new thermal protection system.  Air-breathing hypersonics has consisted over one small test vehicle.   Bush decided to take a journey into the past.

At this point I support Orion because it is clear to me that it is the only way the U.S. will even have a dog in the hunt.  We cant go back 15 years and do it right.  It does allow us to do neat things like go back to the Moon and even serve as a reentry vehicle for a Mars mission.  But for this to be our state of progress after 40 and even 50 years is just shameful. 

I'm not so concerned whether we go forward to the Moon with old tech as I would like to see some major propulsion and vehicle technology development.  We need to develop a reusable earth to orbit transportation system.  We need to actually develop and fly a nuclear thermal system, and to develop and fly VASIMR.  In the 1960s the Russians tried to brute force the Moon mission and failed.  The U.S. pushed technology with the liquid hydrogen fuel upper stages of the Saturn V.  To go to Mars and beyond we need better propulsion in order to reduce mission times.  No one was been in zero gravity/ reduced gravity as long as a Hohmann trajectory would require for a Mars trip using chemical propulsion.  The brute force way risks failure.

-- Edited by John on Monday 27th of July 2009 01:28:15 AM

I agree with both of you--to do this right, we must have the transportation infrastructure--and to do that, we've got to look at near earth comets and asteroids for resources because the gravity penalty lis lowest with them...

Looking at the "Cold Equations" of rockets [deltaV=C*ln(mi/mf)] it becomes clear that going to Mars with any meaningful human mission will require maximizing both "c" and mi/mf (mass ratio) to achieve usable mission velocities...this requires for the bulk of the mass sent to Mars to be shipped 'slower' and longer (read Hohmann Transfer) for cargo-only; and a smaller, lighter and faster transit vehicle (read VASIMR or light NTR.) This seems to imply a two transit vehicle architecture system.

Otherwise, a one vehicle transit system seems to imply a rather large single vehicle to deliver both cargo and people, conceivably at the same time--and this means a long transit flight (Hohmann Transfer) with attendently large consumables load (to support crew for long duration,) and also requires a vehicle with more substantial radiation protection (to shield the crew from solar flare and cosmic radiation sources.)

I am dubius about doing a human mission with only chemical propulsion--it requires a vast effort, comporable in size to what Dr. Wernher von Braun first proposed back in the 1950's. If we are going to do it right--and I think we have to if we want to send people--we have to have nuclear power systems, and nuclear propulsion systems. The CEV/NTR is just about as minimalist as functional Mars architecture can be and still achieve something worth the risk of sending people there...

If we have the rest of the solar system as our eventual human exploration goal then we simply must have that near earth, deep space transportation infrastructure in place. It makes more sense to exploit the water from a hundred billion ton comet nucleus than trying to mine ice on the moon and transport the water from the lunar surface to a point in space where a deep space mission can be fueled, and it makes even less sense to transport that propellant mass directly from the earth's surface. Atleast, not the way we currently can do it.

Hohmann transfers to Low Mars Orbit for cargo (most mass) = minimum energy transfers. Hyperbolic fast transit (lighter vehicle carrying transhab) to low martian orbit. Cargo drop to mars surface base, followed by crewed landing at site =  Mars Surface Rendezvous. The slow cargo, fast human transit scheme is less risky as far as loss of crew...all major base components landed at site, including Crew Ascent Stage is already landed and checked out on surface, before crew even arrives.

Buzz Aldrin's idea of an Earth-Mars Cycler makes really good sense: the actual vehicle stays in a 3:2 resonance orbit between Earth and Mars. Normally this is a dynamically unstable orbit, but a powered vehicle can use small thrusters to keep it in a nominal path. Intersections occur every 2 Mars Revolutions, or multiples of 3 Earth years. Every time an outbound vehicle docks with the "Cycler" it replenishes consumables like propellant, oxygen, food, water and spare parts. In this case the Cycler acts as a place to stay for a while while the vehice traverses inerplanetary space. The delta-V requirement to intercept a cycler is relatively modest, about the same as a Hohman transfer. Ditto for a departure from the cycler with an intercept at Mars. Multiple Cyclers can actually achieve something few other vehicles can offer--frequent, near all time access to the Red Planet for relatively modest delta-V costs.

Cycler is definately not only possible, but I would imagine it would eventually make Earth-Mars transits cheap.