Reusible vs. Expendable - the Real Debate

[vulture4]

A debate rages in the press about the goal of human spaceflight - the moon, Mars, or an asteroid. But in reality they are just different destinations for the same program, as Mike griffin described it, "Apollo on Steroids". Another debate rages over NASA vs private industry. But in reality the Delta, Atlas, Ares, and Shuttle are all built by partnerships of Boeing and Lockheed (BoLo) while the Falcon/Dragon is built by SpaceX, all private companies working under NASA contracts. This battle is really just between different contractors and different groups of NASA administrators.

The real debate is the same as it was in 1974, should NASA develop launch vehicles and spacecraft that are expendable or reusable?

It's a choice that must be made. The goals of the Shuttle and its potential reusable successors, to provide low-cost transport to LEO for large numbers of people and frequent cargo deliveries are quite different from the goals of Constellation and its expendable successors in sending a limited number of manned missions to the Moon, Mars, or an asteroid, and the resources are not available to pursue both. There are various related questions. Is the cost of human spaceflight important to potential spacefarers? What is the curve of cost vs. demand? How many tickets were sold by Space Adventures at $20 million, vs. Virgin Galactic (for a much shorter flight) at $200K? What would scientific researchers be willing to pay to go into space for research purposes if the money actually had to come out of their grants? What is the relationship between price and supply? How would spending on various new technologies move the supply curve? Assertions are widespread that "the Shuttle proves reusable systems are impractical". Is this view correct? What are the sources of the cost of Shuttle operation? Are they intrinsic to any reusable launch vehicle or specific to the Shuttle design? For readers with experience in Shuttle processing, how many ways can you think of to reduce the cost in a new reusable design? Or are we better off forgetting the whole idea? Expendable design is more mature; how much further can the cost be reduced with "clean sheet" designs like the Falcon? Should NASA fund ELV development or simply procure what they need? RLV technology is less mature, can contractors do the development work largely with corporate funds, as was attempted with the X-33 and X-34, or is the risk too high?

 

[rcsplinters]

Good series of questions. I personally don't subscribe to the thought that the shuttle disproves anything regarding viability of reuse. I think the topic of reuse has to be addressed in two contexts. First is crew capsule. I think the shuttle does tell us that maybe combining your heavy lift and crew lift capability in the same bird may not be cost effective. Should that crew capsule be reusable? Orion certainly contemplated that. Given the complexity of a crew capsule, I think reusability is definitely indicated. The second question deals with heavy lift. Just how much if any of the booster needs to be reusable in a 100 ton plus stack? Here I'm not so sure. The shuttle seems to have done very well with reusable motors and solid casings. Have we ever tried reusing a liquid propellent tank? So in the case of the boosters themselves, maybe partial reusability is the correct route.

Another interesting aspect of this is the answer is pretty much an engineering/economics decision. The answer may vary from design to design. Sadly, the question is largely academic since the US is soon to be incapable executing a manned space flight mission with no viable plan for developing that capabilty.

 

[kelvinzero]

I don't have enough knowledge to answer any of those questions but everybody knows enough to be opinionated

I dont think it is so much Reusable vs Expendable as when and how we get to the level of reusables, and are expendables on that path.

Reusables cannot become cost effective until we have pretty high flight rates. If you think biffing a rocket into the ocean after one use is inefficient, think how inefficient it is if you do not need to build another for decades because it is reusable. That is like biffing all the companies and all the people geared to actually designing and assembling such a rocket into the ocean.

However just because reusables are not cheaper right now does not mean don't build them. I would like to keep seeing prototypes being built and launched. We just have to keep designs small enough that we are prepared to write off the cost as money spent on research, not a competitive launch vehicle.

I personally like the idea of evolving each stage of a two stage expendable towards a two stage reusable, independently.

Also I like the idea of fuel depots. It justifies many unmanned launchers with few constraints on the design, which seems a good environment for evolving towards fully reusable solutions.

 

[vulture4]

>>Reusables cannot become cost effective until we have pretty high flight rates.

That's why I brought up supply and demand. At the current cost of expendables, i.e. the EELVs, demand for true commercial launches from US soil is less than 1 per year. SpaceX can do somewhat better. But there is no way to ever substantially expand the market for spaceflight without a substantial reduction in cost, which cannot be achieved with expendable technology. So the only way to increase the flight rate is to provide government R&D funding to develop reusable technology and shift the supply curve. That was the rationale for NASA to fund Shuttle in '74.

The next generation RLVs can be much less expensive than the Shuttle if they are (at least initially) unmanned systems. But if Shuttle is terminated before next-generation RLV development begins, essentially all the people with real hands-on experience with reusable spacecraft will vanish in short order and the time and cost required to re-create the technology will increase substantially. Fuel depots can be a very useful technology for flight beyond LEO, but do not by themselves shift the surface-to-LEO supply curve much, so it's hard to see how they alone can substantially increase the market.

 

[SteveCNC]

One thing I have seen used as reason for expendable is the loss of experienced people once the project is done . Well from my perspective that really isn't as big of a deal as you might think . For one the people you lose from government employ move into private sector or to another section of government , they don't cease to exist . And for the most part if you wanted them back it wouldn't be that hard to intice them in (I'm not as simple to intice but most people are) . Besides that if you can draw it someone will bid on making it , plus I don't see any lack of engineers any time soon . From what I see we are having a bit of a glut of engineers coming out of schools recently , while they are inexperienced they are up on the latest software and techniques (I really hate when a new version completely changes the UI :evil: ).

One thing about expendables is the manufacturing cost is lower just because of the fact that it's far cheaper per part to build 30 of the same part on a 3 year contract than it is to build 6 on a one time build . I used to do Lockheed/Martin components and assemblies and that's typically how it worked with them . So the expendable has it's merits in cost per unit but does it always have to come down to what it costs ? can't it come down to what's right instead ? Expendable is so wasteful to me , to think everything I made for Lockheed/Martin is either sitting at the bottom of the ocean rotting or flying around as space junk is kinda sad and not good for the environment .

While it may cost more per vehicle to have reusible and require a while to pay for itself , if properly done it would be better in the long run .

 

[vulture4]

Good points, SteveCNC. overall cost is critical in any sustainable enterprise, although it was ignored during Apollo. But which would actually cost more for you to make, six rocket components parts on a one-time purchase (with an option to buy more when the inventory gets low) or 30 over three years, assuming similar parts? That assumes the RLV part is good for at least five missions. But suppose each RLV part is good for 20 flights? 30? Suppose there are 20 flights per year? or more? Mass production could lower ELV cost somewhat, but there are still a lot of man-hours and materials in an ELV. Wouldn't there be a point at which the reusable would be cheaper than the expendables it would replace?

 

[kelvinzero]

Oh.. sorry I think I might have missed the point of the OP.

"The real debate is the same as it was in 1974, should NASA develop launch vehicles and spacecraft that are expendable or reusable?"

NASA should be about research that commercial companies would consider too risky but would want eventually. I would actually be more interested in nasa developing small unmanned reusable prototypes than for example a big new engine for heavy lift. The point of these prototypes should absolutely not be to compete with commercial flights, but to help commercial companies eventually make the leap to reusable. Likewise I would like to see Orion continue but also to have the purpose of creating a pool of knowledge and skilled workers for eventual commercial designs rather than competing with them.

 

[scottb50]

NASA should be about research that commercial companies would consider too risky but would want eventually. I would actually be more interested in nasa developing small unmanned reusable prototypes than for example a big new engine for heavy lift. The point of these prototypes should absolutely not be to compete with commercial flights, but to help commercial companies eventually make the leap to reusable. Likewise I would like to see Orion continue but also to have the purpose of creating a pool of knowledge and skilled workers for eventual commercial designs rather than competing with them.

I would agree with the first part but not with continuing Orion as it is. As a vehicle for use Space Orion might be just the ticket and that is something that will obviously needed, but like the Shuttle the more jobs you give it the more complex it gets, the heavier it gets, the more it costs and and the more compromises there are for all the jobs it's given.

Ideally we need a launcher and vehicle that takes people and/or cargo to a LEO Station and returns people and cargo to the surface. Specifically designed and built for that one purpose. What I see in Space is something like the Orion that can serve as the nucleus of other vehicles by adding Modules to it as needed. A LEO Tug would need propellant Modules and engines and a moon vehicle would have additional Modules for propellant and passengers and cargo. Asteroids, Mars and other uses would need more Modules and landing and return vehicles would be designed for that specific purpose, lunar, asteroids and Mars present three different gravity environments, though a moon lander and an Asteroid lander could be pretty much the same.

The best way I see to get to this point is to keep usinf the existing ELV's as they are now used but also use them as the basis for a TSTO launcher. 80% of the design work is done and has been used for years, add an aerodynamic shell and turbo-jet engines to a Delta IV and fly the first stage back for re-use. Use Modules for the second stage with RL-10 engines and recycle the Modules in LEO to build all the vehicles and stations.

 

[vulture4]

Good points; the miniature unmanned reusable prototypes were in the pipeline in the Nineties before we got bored with them.

But wait; Orion isn't reusable. ISRU is pointless if you're throwing away your most valuable resource - spaceships. So why do we have to make a direct entry from the moon anyway? Why not aerobrake into LEO and rendezvous with the ISS? Then refuel from the propellant depot and head back to the moon? Particularly since thanks to Shuttle we now know how to make heatshields that are reusable? Of course Constellation didn't plan it that way because Griffin wanted to throw away the ISS.

Reusables aren't restricted to LEO. We just need different reusables that remain in space. And a place in LEO for everybody to meet. We can fly forever for the cost of the fuel. Wait a minute, isn't that exactly what von Braun and Arthur C. Clark originally suggested in the Fifties? For a start, how about a technology demonstrator that can shuttle between ISS and GEO or lunar orbit using Hall-effect thrusters? Wouldn't that be more useful than planting a flag on Eros?

 

[EarthlingX]

You might find this interesting, i hope it's not too far from the topic :

http://www.spaceref.com : Something Old, Something New, and If We do it Right, Maybe Even Something Bold!

As a long time space advocate, I have found recent events to be extremely disheartening. Before my eyes, I am seeing the battle between the old exploration plan (Constellation), and the new plan put forth recently by NASA and the White House. This is battle is compounded by the fact that it is forcing a Congress unwilling to take on more fights before the election to allow NASA to operate for months under a continuing resolution (CR) for its next budget year.

 

[rockett]

You might find this interesting, i hope it's not too far from the topic :

That's OK. I personally would have posted it on "What is going happen to the US space program now" or "A debate on the funding of manned missions to moon and Mars".

But it was a VERY eye opening read. Fascinating that NASA basicly messed up, not the original program.

 

[EarthlingX]

You might find this interesting, i hope it's not too far from the topic :

That's OK. I personally would have posted it on "What is going happen to the US space program now" or "A debate on the funding of manned missions to moon and Mars".

Yes, it might be better, but here it is.

But it was a VERY eye opening read. Fascinating that NASA basicly messed up, not the original program.

It was not NASA to be exact, it was a person leading NASA. They played him bad and he allowed it. That's why he was probably chosen in the first place.
I think he was a victim of his dream.

 

[kelvinzero]

But wait; Orion isn't reusable. ISRU is pointless if you're throwing away your most valuable resource - spaceships.

The Orion could be somewhat reusable.

Also ISRU is not pointless even if you are throwing away your spaceships. The reason is that every ton of payload, whether expensive payload or cheap fuel, requires you to expend tons of expensive launcher. Thus every ton of fuel you create at your destination instead of lugging there from earth saves you from expending some tons of rocket.

 

[rockett]

It was not NASA to be exact, it was a person leading NASA. They played him bad and he allowed it. That's why he was probably chosen in the first place.
I think he was a victim of his dream.

After re-reading the article, I'm inclined to agree with you. Kind of a shame...

 

[rockett]

Well here they come! Looks like all of a sudden, a "space plane" is NOT such a bad idea. NEITHER is REUSABLE a bad idea!

High-Tech Space Planes Taking Shape in Italy, Russia
http://www.space.com/businesstechnology/plans-new-reusable-space-planes-100603.html

Guess all we had to do to get something done, was QUIT!

 

[scottb50]

Well here they come! Looks like all of a sudden, a "space plane" is NOT such a bad idea. NEITHER is REUSABLE a bad idea!

High-Tech Space Planes Taking Shape in Italy, Russia
http://www.space.com/businesstechnology/plans-new-reusable-space-planes-100603.html

Guess all we had to do to get something done, was QUIT!

I would think the Russians could easily recycle the Soyus vehicles, they land easily enough to protect the crews and the bulk of the vehicle could be re-used. It isn't exposed to sea water so there is little reason not to re-use the basic vehicle.

A space plane is also a good idea if it serves a very limited purpose, reach LEO and return for re-use. True the wings are not needed for takeoff and orbit but they are needed for descent and landing. It's like the F-111 or the F-35, it would be cheaper to build different vehicles for each specific purpose then try to make one vehicle fit four or five different needs.
How many times do we have to do it to see it doesn't work? The Orion, hopefully was, the same thing, a jack of all trades that compromises one area to meet the minimum standard of another. It doesn't work.

 

[EarthlingX]

This is a very nice site, with a lot of details about Russian space :

http://www.russianspaceweb.com/soyuz_acts_origin.html

A concept of Advanced Crew Transportation System, ACTS, also known as "Euro-Soyuz," or Crew Space Transportation System, CSTS, emerged during 2006, when Russian company RKK Energia realized that its proposals to replace the workhorse Soyuz spacecraft with the Kliper reusable glider would be too ambitious for the current level of funding of the Russian space program. As of 2006, Russian Space Agency expected to get nine billion rubles until 2012 for the development of the next generation manned transport, of which, only 500 million would be allocated for the task before 2010. As a result, the agency decided to focus on the development of a modified Soyuz, capable of reaching lunar orbit. Potentially, such spacecraft could serve as a bridge paving the way to Kliper.

Artist rendering of the modified Soyuz proposed within Advanced Crew Transportation System, ACTS. Click to enlarge Copyright © 2006 Anatoly Zak

http://www.russianspaceweb.com/ppts_lv.html

Above: The Rus-M family of rockets, employing the RD-180 engine on the first stage and the RD-0146 engine on the second stage as of April 2009. Variant 1 would use three inseparable boosters on the first stage. Variant 2 would use five boosters, with four strap-on boosters separating earlier in flight, while the central core booster would burn longer by thrusting less than its full capability during the initial phase of the flight and throttling up to the full thrust upon the separation of four strap-on boosters. Variant 3 would employ stretched first stage for a larger propellant load. The fourth variation of the vehicle with a single first stage booster and an upper stage borrowed from the Soyuz 2 rocket would also be possible (not shown). It could deliver six tons to the low-Earth orbit. All four variations would use the same launch facility in Vostochny. Copyright © 2009 Anatoly Zak

and just in case :

Wiki :
Rus-M
Prospective Piloted Transport System

with more links.

 

[Valcan]

Well here they come! Looks like all of a sudden, a "space plane" is NOT such a bad idea. NEITHER is REUSABLE a bad idea!

High-Tech Space Planes Taking Shape in Italy, Russia
http://www.space.com/businesstechnology/plans-new-reusable-space-planes-100603.html

Guess all we had to do to get something done, was QUIT!

I would think the Russians could easily recycle the Soyus vehicles, they land easily enough to protect the crews and the bulk of the vehicle could be re-used. It isn't exposed to sea water so there is little reason not to re-use the basic vehicle.

A space plane is also a good idea if it serves a very limited purpose, reach LEO and return for re-use. True the wings are not needed for takeoff and orbit but they are needed for descent and landing. It's like the F-111 or the F-35, it would be cheaper to build different vehicles for each specific purpose then try to make one vehicle fit four or five different needs.
How many times do we have to do it to see it doesn't work? The Orion, hopefully was, the same thing, a jack of all trades that compromises one area to meet the minimum standard of another. It doesn't work.

Heck wings are dangerous on reentry. But the whole problem with the spaceplane idea isnt about the geometry really its MASS. Every extra bit (wings, landing gear, etc) means more $$ to orbit, less cargo, less people, and more complications.

Its like with the shuttle. Imagine if it was a rocket desgin. Instead of 55,000 lbs to orbit (Max payload) as cargo it turns into 200,000lbs to orbit. A huge difference.

A shuttle to carry people to and from orbit by all means. But dont over do it. Small, fast, light, cheap.

 

[vulture4]

How many times do we have to do it to see it doesn't work? The Orion, hopefully was, the same thing, a jack of all trades that compromises one area to meet the minimum standard of another. It doesn't work.

Heck wings are dangerous on reentry. But the whole problem with the spaceplane idea isnt about the geometry really its MASS. Every extra bit (wings, landing gear, etc) means more $$ to orbit, less cargo, less people, and more complications.

Its like with the shuttle. Imagine if it was a rocket desgin. Instead of 55,000 lbs to orbit (Max payload) as cargo it turns into 200,000lbs to orbit. A huge difference.

A shuttle to carry people to and from orbit by all means. But dont over do it. Small, fast, light, cheap.[/quote]

As mentioned earlier, expendable rockets are not a viable solution for human spaceflight because they are simply much too expensive to be practical. Even SpaceX, which has a launch cost only 1/3 that of Ares and about as low as is possible for a manned ELV, will be unaffordable for tourism beyond one or two billionaires a year. he only thing reusables must have for every flight is the fuel to put them in orbit, and the fuel that puts the Shuttle's wings in orbit costs practically nothing. What costs money is building a new vehicle for every flight. In the case of the Shuttle this includes the ET and the SRBs, which really aren't reused, but salvaged. Costs are not dominated by mass. but by the level of reusability permitted by the design. A 747 (reusable) is far less expensive to operate than an Ares (expendable) although it is larger. Both Apollo and Soyuz suffered parachute failures and parachute landing doesn't have sufficient control for easy reusability; there's always some damage. It's questionable any parachute recovery system can be practical for reuse. On the other hand landing gear provide well controlled landings without damage.

 

[rockett]

As mentioned earlier, expendable rockets are not a viable solution for human spaceflight because they are simply much too expensive to be practical. Even SpaceX, which has a launch cost only 1/3 that of Ares and about as low as is possible for a manned ELV, will be unaffordable for tourism beyond one or two billionaires a year. he only thing reusables must have for every flight is the fuel to put them in orbit, and the fuel that puts the Shuttle's wings in orbit costs practically nothing. What costs money is building a new vehicle for every flight. In the case of the Shuttle this includes the ET and the SRBs, which really aren't reused, but salvaged. Costs are not dominated by mass. but by the level of reusability permitted by the design. A 747 (reusable) is far less expensive to operate than an Ares (expendable) although it is larger. Both Apollo and Soyuz suffered parachute failures and parachute landing doesn't have sufficient control for easy reusability; there's always some damage. It's questionable any parachute recovery system can be practical for reuse. On the other hand landing gear provide well controlled landings without damage.

Quite true, the most efficient design is not a disintegrating totem pole, but a vehicle (regardless of configuration) that can be reused as much as possible. Just think what airfares would be if we junked a passenger airliner after every flight...

 

[Valcan]

As mentioned earlier, expendable rockets are not a viable solution for human spaceflight because they are simply much too expensive to be practical. Even SpaceX, which has a launch cost only 1/3 that of Ares and about as low as is possible for a manned ELV, will be unaffordable for tourism beyond one or two billionaires a year. he only thing reusables must have for every flight is the fuel to put them in orbit, and the fuel that puts the Shuttle's wings in orbit costs practically nothing. What costs money is building a new vehicle for every flight. In the case of the Shuttle this includes the ET and the SRBs, which really aren't reused, but salvaged. Costs are not dominated by mass. but by the level of reusability permitted by the design. A 747 (reusable) is far less expensive to operate than an Ares (expendable) although it is larger. Both Apollo and Soyuz suffered parachute failures and parachute landing doesn't have sufficient control for easy reusability; there's always some damage. It's questionable any parachute recovery system can be practical for reuse. On the other hand landing gear provide well controlled landings without damage.

Quite true, the most efficient design is not a disintegrating totem pole, but a vehicle (regardless of configuration) that can be reused as much as possible. Just think what airfares would be if we junked a passenger airliner after every flight...

Yes but a airliner doesnt have to carry its own air to and from its destination.

Look im FINE for using a small space plane for rerrying people to and from space use it like the X37b. BUT not for cargo. Theres a point to where you make them so large it just becomes uneconomical. Now if they had gone for a shuttle C design for cargo only i would be going off like everyone else probably but they didnt.

Theres just no reason what so ever to use a space plane to send up cargo. It would be like you wrapping up a box full of stuff but the box can walk on its own, talk, fly, navigate in total darkness, and make milk shakes.

Thats basicaly what its like when you send a cargo up on the shuttle.

Until someone builds us a fusion rocket so we can build a REAL space plane or builds something like Halman has stated were stuck with flying poles. Heck i believe even he has stated that stacks are better for the super heavy launches.

 

[rockett]

Look im FINE for using a small space plane for rerrying people to and from space use it like the X37b. BUT not for cargo. Theres a point to where you make them so large it just becomes uneconomical. Now if they had gone for a shuttle C design for cargo only i would be going off like everyone else probably but they didnt.

Theres just no reason what so ever to use a space plane to send up cargo. It would be like you wrapping up a box full of stuff but the box can walk on its own, talk, fly, navigate in total darkness, and make milk shakes.

Thats basicaly what its like when you send a cargo up on the shuttle.

Until someone builds us a fusion rocket so we can build a REAL space plane or builds something like Halman has stated were stuck with flying poles. Heck i believe even he has stated that stacks are better for the super heavy launches.

You missed the key words regardless of configuration in my response. I really don't care if they fly or parachute back like the SRBs, as long as we maximize reusability. The higher the percentage that is reusable, the lower their overall cumulative cost to operate. A good example is the Air Force's Pathfinder RFP, what they are asking for is autonomous first stages that can fly themselves home (if I recall correctly). TSTO reusable configurations are another example.

 

[Valcan]

Look im FINE for using a small space plane for rerrying people to and from space use it like the X37b. BUT not for cargo. Theres a point to where you make them so large it just becomes uneconomical. Now if they had gone for a shuttle C design for cargo only i would be going off like everyone else probably but they didnt.

Theres just no reason what so ever to use a space plane to send up cargo. It would be like you wrapping up a box full of stuff but the box can walk on its own, talk, fly, navigate in total darkness, and make milk shakes.

Thats basicaly what its like when you send a cargo up on the shuttle.

Until someone builds us a fusion rocket so we can build a REAL space plane or builds something like Halman has stated were stuck with flying poles. Heck i believe even he has stated that stacks are better for the super heavy launches.

You missed the key words regardless of configuration in my response. I really don't care if they fly or parachute back like the SRBs, as long as we maximize reusability. The higher the percentage that is reusable, the lower their overall cumulative cost to operate. A good example is the Air Force's Pathfinder RFP, what they are asking for is autonomous first stages that can fly themselves home (if I recall correctly). TSTO reusable configurations are another example.

Have heard some talk of boosters that can fly theselves back. I just dont want a vehicle that takes a month to be readied after every flight and cost 1.2 billion a launch.

 

[rockett]

Have heard some talk of boosters that can fly theselves back. I just dont want a vehicle that takes a month to be readied after every flight and cost 1.2 billion a launch.

One article I read says the Air Force estimates that reusable can cut launch costs by 50%.
Here's the RFP and a few articles (of many):

Reusable Booster System (RBS) Pathfinder
Solicitation Number: BAA-10-04-PKV
Agency: Department of the Air Force
Office: Air Force Materiel Command
Location: AFRL - Wright Research Site
https://www.fbo.gov/index?s=opportu...d70cefef43f595557fbe76c0db4&tab=core&_cview=1

Air Force Wants Its Rockets Back
A new prototype rocket could give the Air Force a round-trip ticket to space by 2013.
http://news.discovery.com/space/air-force-reusable-rockets.html

Air Force Calls for Reusable Booster Vehicles for Military Space Planes
http://www.popsci.com/technology/ar...usable-booster-vehicles-military-space-planes

USAF Plans Reusable Booster Demonstrators
http://www.aviationweek.com/aw/generic/story_channel.jsp?channel=space&id=news/asd/2010/04/12/10.xml

 

[vulture4]

Theres just no reason what so ever to use a space plane to send up cargo. It would be like you wrapping up a box full of stuff but the box can walk on its own, talk, fly, navigate in total darkness, and make milk shakes.
Thats basicaly what its like when you send a cargo up on the shuttle.
Until someone builds us a fusion rocket so we can build a REAL space plane or builds something like Halman has stated were stuck with flying poles. Heck i believe even he has stated that stacks are better for the super heavy launches.

1. The fuel for an ordinary chemical rocket like the Shuttle is cheaper than gasoline.
2. An ELV is a $150 million box that can walk on its own, talk, fly, navigate in total darkness, and make milk shakes - that you throw away after using it just once. Bigger ELVs aren't cheaper. An RLV is the only way to significantly reduce launch cost in any payload class.
3. With modern control systems there is no need for an RLV to be manned. The current DOD initiative is for an unmanned reusable satellite launch vehicle. It would cost slightly more than an ELV but be reusable many times with minimal maintenance. The initial version (i.e. the X-37 with a reusable booster) is not intended to carry anything larger than a functional test cargo. It is intended to develop andtest technologies for reusable vehicles.
.