neviden - 30/11/2007 5:53 PMI agree with meiza. But the whole NEP concept doesn't even need 200 MWe to be useful. Even 10 MWe with present technology would work almost as good as chemical/NTP and allow reusable spaceship capable of reaching Mars orbit and returning back. Anything with more power and better kW/kg ratio would only shorten transit times, increase payloads and increase capabilities.
neviden - 2/12/2007 4:43 AMI agree that VASIMR could use lots and lots of power and that more power at lower weight will improve capabilities. Better reactors and more efficient power conversions will do both of those things.But the thing that is holding VASIMR back is that it is used in the wrong way. It is almost like NASA always asks themselves: “OK, how will this technology help us in going to Mars. You know, something like Apollo.. “. So that means that is not absolutely needed is “impossible”.. Reuse? “impossible”.. Existing launchers? “impossible” Space refueling? “impossible” Long term space flight? “impossible”Growing food? “impossible”Artificial gravity? “impossible”So all plans for VASIMIR start at LEO, they must race to Mars at full speed (you know, because it is “impossible” to create 1 g environment in space or carry enough shielding to protect the crew) and return back. That means 200 MW space propulsion with minimum mass.. Reuse? Oh, that will come after that.. when they throw everything in the trash and start on completely new design in 50 years or so..
wingod - 2/12/2007 8:26 PMRemember Babylon V and the Earth starships?
wingod - 2/12/2007 8:26 PMA VASIMR would be the first step down that road.
Lampyridae - 2/12/2007 6:37 PMWhat is really needed is a change in directive, as well as management in NASA. Bush said "go back to the moon, and then go on to Mars." That's exactly what they're doing, although flawed thinking and a lack of plain old common sense has landed them with the Ares problem. What would have been the easiest thing? Build a SDLV with oodles of power by banging on engines to the external tank. But no, NASA's doing the complicated thing because it looked easy at the time - and to carry out their directive given to them by the boss (George 2.0).If George 2.0 had said "develop a sustainable lunar architecture," then NASA would have done it in a sub-optimal way, because they're about science and tech, not space economics. What NASA is doing right now with COTS and what's going on with the various X- and Google-prizes is in my opinion the best thing.Sending cargo to the moon with low-cost, existing rockets would be far more expensive than doing it the NASA way. This has been discussed many times over:1. Massive infrastructure upgrades needed to support required launch volume2. Minimum mass requirements of systems which do not scale down well mean smaller payload fraction (e.g. avionics - you can't have 1/10 of an avionics box; also minimum thickness for fuel lines, nozzles etc)3. Minimal economies of scaling4. Fixed per-launch support costs (e.g. mission control requires almost the same staff for big rocket as a small one)With all this a Dnepr could land maybe a 10kg payload on the moon for $10 million. A Falcon 9, OTOH, maybe 1 tonne for $100 million? That's an order of magnitude $/kg costs. Rather go with big commercial rockets, build up the robotic infrastructure as you suggested, and then land crew using dirt-cheap rocket chairs from orbit, much like the private lunar base plan. But leave NASA out of it, except to provide competition money. Further down the road, if someone invests $10 billion and 10 years into Skylon, then maybe after another 10 years we'll have a system which can do $1000/kg. Note that Skylon is only slightly more cost-effective as Falcon 9 Heavy, but has a lower payload mass. Hypersonic SSTO will only be an outgrowth of suborbital / hypersonic travel, nobody's going straight from A to Z.
neviden - 2/12/2007 3:21 PMQuotewingod - 2/12/2007 8:26 PMRemember Babylon V and the Earth starships? Babylon V style space station would actually be quite a good idea to have in LEO or even better in HEO. And it would not require anything high tech that we would not be able to do right now. All we would have to do is create a thick (crude) metal cylinder and rotate it. After that you can fill it with air and you have a safe place just like Earth.Earth starships that would look like Omega class destroyers or Leonov from 2010 are also quite possible and something that would actually work (without hyperspace stuff of course).Quotewingod - 2/12/2007 8:26 PMA VASIMR would be the first step down that road.VASIMR is not the only propulsion technology. There are many plasma drives possible. I think it would be better to start with smaller, cheaper spaceships that would not cost that much (200 MW seems like an overkill) and upgrade them later. What is important is to actually start using those new things. NASA will get $15 billion to spend no matter what it does. While it may seem like a good idea to throw money at Ares I and V, I think that this is complete waste of money. Even Ares V that might even make sense is a waste of money, since it will promote “hey, why bother with refueling and all that stuff! Let’s just build it, launch it and dump it.. “. There are plenty of perfectly good launchers already operating and completely underused. 20 MW electric spaceship would be more then able to do basic things and would be (more then 200 MW) price competitive with chemical option. That is the thing that is important, not what kind of reactor you have or how much time you spend in ship.. or at least.. it should be..
advancednano - 3/12/2007 12:48 AMThe topic of how NASA or the other space or government programs should spend there money is a separate topic.
advancednano - 3/12/2007 12:48 AMNasa should use existing rockets like the russian Dnepr or SpaceX rockets ($10 million per rocket) and send a constant stream of rockets to the moon using low energy orbital transfers.
advancednano - 3/12/2007 12:48 AMOnce all the facilities are built up we can look at when it makes sense to send people.
Lampyridae - 3/12/2007 1:37 AMSending cargo to the moon with low-cost, existing rockets would be far more expensive than doing it the NASA way. This has been discussed many times over:
Lampyridae - 3/12/2007 1:37 AM1. Massive infrastructure upgrades needed to support required launch volume
Lampyridae - 3/12/2007 1:37 AM2. Minimum mass requirements of systems which do not scale down well mean smaller payload fraction (e.g. avionics - you can't have 1/10 of an avionics box; also minimum thickness for fuel lines, nozzles etc)
Lampyridae - 3/12/2007 1:37 AM3. Minimal economies of scaling
Lampyridae - 3/12/2007 1:37 AM4. Fixed per-launch support costs (e.g. mission control requires almost the same staff for big rocket as a small one)
Lampyridae - 3/12/2007 1:37 AMWith all this a Dnepr could land maybe a 10kg payload on the moon for $10 million. A Falcon 9, OTOH, maybe 1 tonne for $100 million?
wingod - 3/12/2007 1:56 AMI am thinking about their large transportation vehicles that had the spinning section for the humans.
wingod - 3/12/2007 1:56 AMThe B-V space station is a bit down the road.
advancednano - 3/12/2007 11:30 PMPeople don't get smaller but if we are only sending people after we have stuff built out then the cost and number of trips would go way down.
neviden - 3/12/2007 6:13 PM{snip} Starting in LEO orbit would have to be a little higher than NEP, but then again everybody would get very nervous if NEP got to close to Earth. {/snip}
advancednano - 5/2/2008 12:37 PMUsing fuel depots in low earth orbit would increase the payload that could be delivered to the moon by 3-15 times. This would make the many smaller cheaper approach more feasible and effective
advancednano - 5/2/2008 6:49 PMAs part of the thread (this thread) about Vasimr there was a discussion about how money is currently spent on space (whether Vasimr should be funded or other things). I mentioned that a lot of cheap rockets would be better than spending many billions developing just another chemical rocket like Nasa is doing now. Then it was pointed out that cheap rockets would not be able to deliver much payload to the moon. The space fuel depot would be an affordable system and architecture which would help enable the use a bunch of cheap rockets to do more in space approach. Relating to Vasimr in that any advanced system is within the context of doing more in space cheaper and sooner.