sferrin said:
mz said:
Well, currently Atlas V and Delta IV can do it. Not in one launch of course, but that's a separate question that has to be examined rationally (which has not been done by NASA).
You sure about that? I'm pretty sure they didn't just draw a number out of a hat and base their decision on that.
I'm afraid the ESAS study was not entirely rational. They assumed that in a multi launch architecture you can use only one launch pad and you won't use a propellant depot - hence a single launch delay or a failure would break the whole mission.
Everyone listen to the Augustine Panel's Beyond LEO subgroup's report (it's under a week old) on how to *really* do things:
http://vimeo.com/6037790
Besides, if you went with the Delta IV Heavy (The Atlas V heavy is a paper design) you're taking about six launches vs one. (Not just launch vehicle cost but the cost of the launch itself.) Also, now you'd have to design with that 50k or less limit and hope to dock everything together in orbit (more risk). Add to that your diameter limits and the problems it brings with it and it wouldn't surprise me if it were more expensive AND less capable.
That depends. This approach was never analyzed. Note that even the current vehicles are all below 25 t in weight, if you take the liquid oxygen out of the EDS and LSAM.
The current Ares approach already has two launches.
If you are using a depot, you don't really need to count propellant launches as the depot can have margin and redundancy.
The crew and exploration hardware (EDS, LSAM, Orion) could go up in three launches. Thus no dramatic difference.
Soyuz, Shuttle, ATV, Orbital Express. Docking in space is a well demonstrated technology today, unlike in the sixties when the Apollo missions were designed.
And one point, Atlas V heavy is still much further in design than Ares I. The boosters manufactured today are capable of the heavy configuration I'm told - their design philosophy was not to make them customized like with Delta IV.
I don't know what work would be required. I have heard 18 month timetables but that could be hubris.
mz said:
In the near future possibly Falcon 9 and Taurus II.
Taurus II? Are you joking? You want to try to mate up TWENTY launches in orbit? Good luck.
We don't know how launching propellants scales, as it has been studied very little. NASA has overlooked it historically.
And I'm not saying one should use *only* Taurus II to launch propellant. (Or people or supplies or whatever.)
I'm somewhat sceptical of it's usefulness, though it could do much better with a better upper stage. It's not designed for high launch rate anyway since the first stage engine supply is finite, and it's a Delta II cheaper-at-low-rate replacement at the same time.
mz said:
Abroad, Ariane, Proton, Zenit, H-II, Long March, launch multiple times every year etc etc...
All of which are non-starters.
They could parttake in sending up propellants. It's an option. Russia and Europe already supply the ISS. Soyuz and Progress proved vital when STS was inoperable. I wouldn't dismiss this offhand.
Russians and Europeans seem to do quite well on the open but security conservative expensive comsat market too.
mz said:
I'm not a fan of BDB:s - they would fly so rarely that that they would be expensive anyway. For example ships costs a lot but they recoup the investment by operating for a long time.
Refuel and go again level reusable launch vehicles are what's needed to reduce space access cost by an order of magnitude. They do not require any fundamentally new technology - moderate rocket engines are enough.
The problem is NASA and the gov are plagued with a terror of risk. They practically wet their pants at the mention of the word. The result is nothing of note ever gets done or accomplished other than blowing through a lot of money. NASA should have taken the DC-X as far as it could. At least PROVE the thing doesn't work instead of giving up at the first sign of success.
Yes, NASA should do multiple smaller programs as technology exploration that would be allowed to try and fail, instead of banking everything on one gigaprogram.
Government research and private application have enabled good improvements in many technology fields and could do it for space as well.