meiza - 26/1/2008 11:31 AMDavid, he probably means nuclear thermal rockets (NTR) which run on hydrogen only. Their use is outlined in the Mars reference mission 3.0.
Zach - 26/1/2008 6:18 PM NTR is certainly the likely interpretation of Griffin's comment. But if Griffin believes that hydrogen boilof is a key limiting technology in an NTR world he has his priorities mixed up: "control of hydrogen boiloff in space is one of the key limiting technologies for deep space exploration". Development of the reactor, human rating it, getting approval to launch said reactor, and operating it, especially in Earth orbit make hydrogen storage pale in comparison.
Note that he said 'one of' not 'the'. All the enabling technologies have to be in place for something to be enabled. A reactor that lacks fuel because it has all boiled away is going to look pretty silly, as is a stock of LH with no way to make use of it.
The thing with control of boiloff is that it is 'dual use' - the technology benefits both Chemical and Nuclear Thermal propulsion.
Rick
sbt - 27/1/2008 6:23 AMQuoteZach - 26/1/2008 6:18 PM NTR is certainly the likely interpretation of Griffin's comment. But if Griffin believes that hydrogen boilof is a key limiting technology in an NTR world he has his priorities mixed up: "control of hydrogen boiloff in space is one of the key limiting technologies for deep space exploration". Development of the reactor, human rating it, getting approval to launch said reactor, and operating it, especially in Earth orbit make hydrogen storage pale in comparison.Note that he said 'one of' not 'the'. All the enabling technologies have to be in place for something to be enabled. A reactor that lacks fuel because it has all boiled away is going to look pretty silly, as is a stock of LH with no way to make use of it.The thing with control of boiloff is that it is 'dual use' - the technology benefits both Chemical and Nuclear Thermal propulsion. Rick
jongoff - 23/1/2008 2:18 PMWhile one could definitely draw the conclusion that Griffin drew, ie. that hydrogen boiloff issues imply it would be better to launch the system in fewer pieces, one could also draw a different conclusion. The conclusion I would draw is that if cryogenic propellant storage technologies are so critical--develop them.
While one could definitely draw the conclusion that Griffin drew, ie. that hydrogen boiloff issues imply it would be better to launch the system in fewer pieces, one could also draw a different conclusion. The conclusion I would draw is that if cryogenic propellant storage technologies are so critical--develop them.
Norm Hartnett - 23/1/2008 1:30 PMThis speech is one of the reasons I respect Dr. Griffin. The man can really put together a good speech and this year he has done several of them. I still consider him one of the most dynamic leaders NASA has ever had.I would like to challenge both the DIRECT group and the EELV group to respond to this speech on a point-by-point basis.Good luck.
Lampyridae - 31/3/2008 7:49 AMThere are other things to feed NTRs... such as Ammonia, Isp of about 600 compared to 800 for LH. That would do for return propellant.
neviden - 31/3/2008 12:23 PMQuoteLampyridae - 31/3/2008 7:49 AMThere are other things to feed NTRs... such as Ammonia, Isp of about 600 compared to 800 for LH. That would do for return propellant.In that case they are better of with simply using chemical rockets. NTRs are borderline useful as it is with 800 s.If NASA thinks about going nuclear then NEP presents much better option. But if they would develop electric propulsion system in MW range, they could even remove the need for nuclear reactor and go with SEP.
Lampyridae - 1/4/2008 3:36 AMYou are putting all your eggs in one basket with a big launcher, but unlike eggs you can't make a Mars ship omelette with 5 eggs instead of 6. ISS is a 4 egg omelette when it was meant to be 6, after all. And it's still not ready to be served.
Lampyridae - 1/4/2008 3:36 AMNow, with the Europeans and Russians, neither seem about to stump for a new, larger launcher but both are keen on the moon. The only approach I've ever seriously heard is along the lines of EELV.