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8/20/2006: AN ALTERNATIVE LUNAR LAUNCH ARCHITECTURE

moon1s.jpg (12666 bytes)NASA has a plan to return humans to the Moon. 

It seems that every armchair space quarterback with an Internet connection also has a plan.  

I have a plan too.  And, like every other non-NASA lunar mission architect, I am convinced that my plan is better than NASA’s. 

Here is my plan.

NASA plans to develop two brand new launch vehicles: a 25 tonne to low earth orbit (LEO) crew launch Ares I and a heavy lift 130 tonne to LEO Ares V, an effort that, based on past projects of the type, could end up costing more than $20 billion.   

My plan would be to develop only one brand new launch vehicle, slashing launch vehicle development costs in half.  $10 billion is real money, even in 2006.  That is $400 million per year if spread over a 25-year-long program.

O.K, I’m making a grand assumption (guess) about the amount of development cost savings, but you get the idea.

NASA plans to launch one Ares I and one Ares V for each lunar mission, putting about 150 tonnes of crew spacecraft, lunar lander, trans-lunar injection (TLI) stage, and propellant into LEO.   NASA calls the crew spacecraft “Crew Exploration Vehicle” (CEV).  It calls the lunar lander “Lunar Surface Access Module” (LSAM).  It has named the TLI stage “Earth Departure Stage” (EDS).  All of this mass will be docked together in earth orbit to be accelerated toward the moon.

My plan would do the same thing, but in a slightly different way.  I would launch two identical, but smaller-than-Ares V, 90-tonne to LEO rockets for each mission.  One of these would haul a fully-fueled TLI stage.  The second would boost the lander and crew carrying spacecraft. 

Why 90 tonnes?  Because that is sufficient to haul the heaviest component of the mission:   a fully fueled TLI stage.  Orbital mechanics calls the shots.  A crew vehicle and lander together will always weigh less than a fully fueled TLI stage for this type of mission architecture.  The combined post-TLI CEV/LSAM mass will reportedly be more than 65 tonnes.  (Apollo’s Command/Service Module and Lunar Module weighed about 45 tonnes combined, but NASA’s new lunar plan calls for longer stays on the moon and for access to a wider range of landing sites.) 

O.K., the dual-launch architecture isn’t exactly *my* plan.  It is NASA’s plan, pulled from the pages of the famous Exploration Architecture Systems Studies report issued in November 2005

It is right there in Figure 1-11 on page 18 of the Executive Summary.  That it costs less than the “1.5 Launch” plan NASA selected is shown quite clearly in Figure 1-15 of the same Executive Summary and in Figure 12-10 in Chapter 12.  There are other charts in there somewhere showing how the dual-launch plan is about as safe as the 1.5 launch plan, etc.

Now, to make my plan differ from NASA’s, I’m going to eliminate an entire contractor chain from the project.  For starters, I’m not going to use shuttle-derived solid rocket boosters at all.  In fact, my rocket won’t use strap-on boosters of any kind. 

Instead, I’m going to build a simple two-stage cylinder and load it with liquid propellants.   The first stage will either use seven RS-68 main engines or, if an American production line can be established for them, six RD-180s.   The second stage will use three or four of the same J-2X engines that NASA is currently planning for powering the Ares upper stages.

If powered by seven RS-68s (essentially an SRB-less Ares V with two more RS-68s), the dual launch vehicle would stand 98 meters tall and would be 10 meters in diameter.  It would weigh 1,700 tonnes at liftoff, but would only weigh about 270 tonnes empty (including the 90 tonnes payload), simplifying pre-launch processing.  A six RD-180 version might use shuttle external tank tooling (8.4 meters diameter) so that it would only stand about 80 meters tall.  The latter rocket would weigh 1,900 tonnes loaded, but only 143 tonnes empty.  

NASA’s Ares V, by comparison, is projected to stand 114 meters tall and weigh nearly 3,500 tonnes at liftoff.  It would weigh more than 1,800 tonnes before liquid propellant loading even starts, about the same as the entire loaded gross liftoff mass of one of the the dual launch vehicle!  

The seven RS-68 engine idea is borrowed from Henry Spencer, the great Usenet space guru, who posited an ET-based “Brown Bess” launcher for the dual-launch mission a year ago or so.    

The lightweight dual launch vehicles would weigh less than a shuttle stack, eliminating the need to build all-new launch platforms at Kennedy Space Center’s Complex 39 as NASA will have to do for the ultra-heavy Ares rockets.  Indeed, these rockets would not need Complex 39 at all.  Most of the facility could be retired, like the massive Vehicle Assembly Building and the crawler transporters, in favor of assembling the rockets at the launch pads.  Or, especially if RD-180s could be used, the program could use an automated horizontal processing setup similar to the methods used by Sea Launch Zenit, erecting the rockets shortly before launch to eliminate the need for massive service towers at the pads.

How much would a launch cost?  My guess would be that the “launch services” cost for each of the two-launch lunar missions would be, at a minimum, no more than NASA’s planned “1.5 Launch” mission, but that doesn’t include the initial $10 billion development savings.  I suspect that the launch vehicle would actually end up costing less to build and fly than Ares in the long run.  It would fly twice as often as either of NASA’s Ares rockets, doubling manufacturing productivity.  It would use a smaller contractor base than NASA’s Ares, cutting overhead.  It would require a much smaller launch site (and staff) than Ares, reducing overhead even more.

“But wait,” you say, “What will NASA use to launch crews to ISS?” 

Shuttle is doing the job until 2010.  Soyuz could handle the mission after that.  NASA is expected to pull out of the ISS project after the lunar missions begin in 2016 or thereabouts.   It doesn’t make sense for NASA to develop an all-new launch vehicle that would only fly for a few years.  Dual launch vehicle could, of course, handle the job once it entered service.   I know - it seems overkill.  But remember that the dual launch vehicle will weigh less, and likely cost less, than the space shuttle that NASA is currently using for the same mission.

So there it is, for whatever it is worth.  That’s how I would do it. 

- Ed Kyle