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Showing posts from August, 2011

EML1 Buildup

Today's space launch market is used to place satellites - commercial, scientific and military - into orbit, with the majority going to the geostationary orbit. In all such cases, the launch vehicle does not perform the final maneuver to circularize the orbit. The satellite is dropped off and circularizes its own orbit using on-board propellant. This is a significant delta-v change of about 1.6 km/s, and the remaining fuel is used to maintain the orbit, usually for 25 years or more.

Launch to Geostationary Transfer Orbit, circularize using on-board propellant. This is the standard model for how satellites are deployed into space. It is a mature process which has served us well for decades. However, when planning an exploration architecture, it has always been treated as irrelevant.

Here is a list of some current (and one near future) launch vehicles, their listed throw mass to GTO and the calculated mass that can be placed into the first Earth-Moon Lagrange point using a 312 …

Dreaming About NASA Mismanagement

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There's so many things packed up in this clip. For a start, the House isn't trying to cut the James Web Space Telescope (JWST) because "we don't have the money" or to save money or for any budgetary reason what-so-ever. The House is trying to cut JWST because the Government Accountability Office reported that NASA, and the contractor, have been mismanaging this program. They reported this three different times and required reports on what NASA was going to do about it - NASA didn't provide those reports. The House even said that the reason they were looking to cut JWST was to send a message that ignoring oversight will not be tolerated.

Does that mean the JWST isn't important? No.. no-one is saying that. Everyone agrees that JWST is important and that it will give results of significant scientific discoveries should it ever be completed and launched.. but when will that be? Within a two week period - after the House suggested cutting the budget - …

We've Already Got Propellant Depots

The solution to so many space logistics problems is: use a bigger rocket. Propellant depots allow you to add another solution: use more rockets.

Now, for some reason, many people who are advocates of propellant depots object to just using existing space storable propellants because that would mean you'd need to launch more mass than if you used cryogenic propellants. Well, so what? More launches - that's a good thing!

We don't need technology development to make propellant depots work. They already work.. we already have one in orbit!

Suppose you want to send 100 tons to Mars transfer orbit. You need either 236 tons of storable propellant or 144 tons of cryogenic propellant (and that's being overly generous to cryogenics). Instead of 5 Falcon Heavy launches you now only need 3. So what? How much is that worth?

So, ya know, NASA has selected companies to study storing cryogenic propellants in space.. and that's great. Technology development, in general, is fantasti…

All we need is a really long tether!

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I've written previously about non-rotating artificial gravity in Earth orbit. After recently watching this stinker I broke out the code I use to figure out gravity gradient effects. Surprisingly, this seems pretty good:




AltitudeMassGravityLEO Station300 km273 tons0.999 gGEO Station35786 km30 tons0.38 g

Of course, this is a much longer tether than in the film.. but hey, Danny Baldwin is in it - he doesn't make good movies. Anyway, the high station could be an ISS-style module with airlock and docking ports for satellite servicing vehicles. The low station would be a true permanently inhabited facility where people can live for years at a time without fear of bone mass deterioration or the other negative effects of zero gravity. To maximize space we may be tempted to use inflatable Bigelow modules, but we have to consider how they will behave in full gravity.

The only sticking point left is radiation. On the LEO station crews have much less exposure to cosmic radiation than…