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Finish the X-33

Thank you for your editorial to revive the X-33 program. Our first priority should be developing a reliable, inexpensive means to Low Earth Orbit (LEO).  Your assertion that we cannot spend billions of dollars on a new reusable launch vehicle (RLV) program is absolutely correct.  For example, why is President Bush’s return to the moon to occur in 2015–2020 (11-16 years from now) when President Kennedy committed us in 1961 and we landed in 1969?  Because the generous space budgets are a thing of the past.  Experts say only a crisis like an asteroid on a collision course with Earth would substantially increase funds for space.  This threat is another reason we need a robust space infrastructure, but that is another issue for another time.

The X-33 revival ultimately could aid missions to the Moon and Mars.  A ramp-assisted Venturestar could carry the proposed crew exploration vehicle (CEV) on its back into LEO.  Existing boosters like the Atlas V and Delta IV could carry much heavier payloads with a ramp assist.  This would mean fewer launches would be needed to assemble spacecraft in orbit, reducing risk. In fact, Uncle Sam wants your help on the new space program.  Citizen suggestions may be submitted at www.moontomars.org.

                                                                                     Phillip Park

Ed: NASA needs to experiment with large suborbital RLVs if any progress is to be made.  

NASA Can't Succeed

I have to disagree with you conclusion on this one. The X-33 had a lot of issues with it, and reviving it wouldn't likely result in a useful orbital RLV anytime in the foreseeable future.  The problem as I see it is that NASA and the big government contractors like Boeing and Lockheed Martin are so steeped in bureaucracy that it makes it very difficult for them to do anything inexpensively.  I do agree though that the shuttle was a flop.

I think a better solution would be to get NASA out of the earth-to-orbit launch industry, and just have the put out a request for launch services of some sort.  Near term they'd probably end up flying EELVs, but if they put an open offer to anyone who can supply them with the capability, you'd likely see real improvement.  Several companies are working on lower cost orbital access, such as SpaceX (www.spacex.com), which just unveiled its new semi-reusable Falcon I.  It is capable of putting up a bit more than a Pegasus launch vehicle, but at somewhere around 1/4 the price.  They're working on a Falcon V follow-on that will be offering prices that even the Russians will have a hard time matching. 

There are also other groups working on this problem, like SpaceDev, Interorbital Systems, Microcosm, etc.  I think the best thing NASA could do is let the market solve the problem and just buy from whoever can provide launch services at a good price.  Sure it may not give a fully reusable launch vehicle immediately, but seeing NASA et al's track record with RLV development doesn't really give me much hope that they could actually pull something off successfully.  To quote Jeff Greason from XCOR Aerospace (a company focusing on reusable suborbital vehicles for commercial applications), "It's hard to reduce costs by spending a bunch of money, or to increase reliability by adding a bunch of stuff, but unfortunately that's all NASA knows how to do".  So to sum it all up, I think we ought to let the private space launch
market have a chance at this. 

                                                                                       Jonathan Goff

Keep the Shuttle Fuel Tanks in Orbit

I'd add one almost no-cost change to the remaining Shuttle program, given the President's announced change of focus.  Since all remaining Shuttle missions will now go to ISS (unless the last Hubble service mission is revived), it is now time for NASA to stop de-orbiting the Shuttle's main tank. 

You know as well as I do that a Shuttle with a fully refueled main tank could take a huge load to the moon, and do so very quickly.  With this sort of incrementally growing facilities capacity a different possible end for the remaining Shuttles appears.  This is to leave them in orbit after their final missions to serve as space tugs. Put another way, what tablet is it engraved on that the Shuttles are predestined to end their days on Earth at the Smithsonian and decorating lawns at Kennedy Space Center and Houston Spaceflight Center?

The final Shuttle missions should not be flown until after an alternate crew vehicle is operating.  And in preparation for these final missions each remaining Shuttle should be outfitted for as extended a period of orbital and Earth-Moon service as physically possible.  So the initial steps in a permanent manned space presence are:

1.  Assemble the LEO fuel tank farm near the ISS using already orbited Shuttle tanks, instead of deorbiting them.  

2.  Aggressively search out and recover water bearing NEOs for use a fuel sources.

3.  Develop a follow on crew vehicle and also unmanned cargo vehicle using Skyramp Technologies for assisted launch.   A Skyramp can only launch in one direction.  This uni-direction implies a routine destination, such as the growing ISS/Tank Farm complex developed under #1.  A coherent articulated strategy like the above also overcomes the obvious objection that a Skyramp can only launch in one direction.

4.  Launch permanent moon base mission.  Perhaps using one or more Shuttles w/refueled tanks to boost  the colony's equipment package?   This is a reasonable 2010-2011 goal if we start today.  And it starts by reorienting the focus of what's already being done with already paid-for equipment.

                                                                                               Mark     

Ed: Here is a good recent article:  Is the Shuttle Grounded Forever?

X-33 Not Needed

The February edition of G2mil quotes Peter B Teets '"we are probably only two inventions away' from success" [on the X-33 Venturestar].  The X-33 program, at the time it was cancelled, still lacked an adequate propulsion system and a payload bay.  These are not trivial problems, as the editor seems to imply.  Even if these problems can be solved, the X-33 would not be significantly better than the space shuttle.  Instead we should switch back to disposable rockets.

Before we decide to spend billions developing a new spacecraft we need to think about what type of missions we want to perform. 
1. Deploying satellites in Earth orbit
2. Deploying robotic probes for deep space exploration
3. Ferrying humans to and from orbit including the international space station.  
4. Manned space exploration 

Missions to Earth orbit can be performed more cheaply by Europe, Russia, and China than by the U.S.  The international space station is configured to dock only with the space shuttle, but this could be changed in a single mission. The Saturn V rocket used during the Apollo missions is the only vessel in history that has ever performed real manned space exploration.  Robert Zubrin's Mars Direct Program could send humans to Mars and back using the equivalent payload of two Saturn V launches.   http://www.marssociety.org/

The idea of a reusable launch vehicle was originally conceived to save money, but it didn't work that way in practice.  The shuttle requires comprehensive examination between flights, including examining every tile of the heat shield for microscopic cracks.  It costs more money to prepare the shuttle to fly again than it does to build a brand new Saturn V!  The operations and maintenance budget for the X-33 would be almost as high as the space shuttle, the only savings would be on the external fuel tank.   A re-usable vehicle also requires wings and landing gear, which adds a lot of extra weight and reduces effective payload.  Disposable capsules with parachutes are much lighter, cheaper and fully effective.

NASA should switch back to disposable rockets that can reach orbit inexpensively, and are capable of reaching out to the moon and Mars.  Because NASA has over forty years of experience with this technology, development costs would be small.  NASA could even afford to operate two vehicle systems:  a light rocket for reaching Earth orbit, and a heavy rocket for going to the moon and Mars.  The most important question is: "What type of missions do we want NASA to perform?"  If all we want is a manned orbiter, then the X-33 might be worth finishing.  But if we want a real spaceship we need heavy lift rockets.

Personally I would like to see humans land on Mars within the next forty years.  President Bush wants to build a permanent lunar base.  Both of these goals require heavy lift rockets.  Putting men in low Earth orbit is not a very good investment.  Except for the missions to repair/upgrade the Hubble telescope, I cannot think of any shuttle missions that have resulted in important scientific discoveries.  Can you?

You're right about the new titanium shielding tiles for the X-33, this should be cheaper to maintain than the shuttle's heat shield.  Lets assume that attaching the payload to the nose would not cause any serious problems.  That still leaves the problem of propulsion.  Aerospike engines were invented during WWII but the problem of overheating has not been solved.

The shuttle has recurring costs over $20,000/lb, the Saturn V costs about $3800/lb in today's dollars, estimates for the X-33 range between $1,000-$10,000/lb.  I hesitate to believe the lowest estimates from government contractors, so it's still unclear whether the X-33 would be cheaper to operate than the Saturn V.

I'm not suggesting we duplicate the Apollo missions exactly, nor that we build an exact replica of the Saturn V.  I am suggesting that we build a system to go to Mars, a subset of which can be used for going to the moon.  To accomplish this we need a heavy lift rocket in the class of Saturn V.  If the new heat shields are as good as promised then the capsules could be reused, further reducing cost.

                                                                                              Ben Harp

Ed: Few Americans understand that we officially lost the Space race last year when Boeing and Lockheed-Martin announced they will no longer bid on commercial contracts because it's not profitable.

Going to Mars

A reasonable plan to go to Mars has already been around for a decade.  It's been called "Mars Direct", since it is an Earth-to-Mars mission, with no detour to the moon.  You should take a look
http://www.sciam.com/article.cfm?articleID=00087E38-5B46-1C75-9B81809EC588EF21

The technology needed to accomplish the mission has been around since 1990, and the mission would cost only a fraction of Bush's plan to go to Mars using the moon as a base.

                                                                                      G. David Nystrom

Ed: Going to Mars is not that difficult; getting home is the challenge.  Unlike the moon, Mars has substantial gravity so a massive spacecraft must be assembled there to blast off back to Earth.  A reasonable plan is a one way trip.  I'm sure thousands of 65-year olds would volunteer to land on Mars knowing they will never come home.  Just send them food and television signals until they die naturally at the Mars base.  This is a more interesting way of spending one's "Golden Years" than in a retirement home.