It needs LHe and not propellant. LHe is not a ISRU commodity. Also, it is not an orbit conductive to servicing. Cheaper to launch an upgraded observatory.
@ Lar,The point Jim is making is that it is pointless talking about what might be available in the future as the spacecraft is unlikely to remain serviceable long enough for a servicing vehicle to be funded, designed, built and deployed. That's assuming that it is possible to service Herschel in space, which I bet isn't the case.There is an argument for designing future observatories to be upgradable and maintainable the way HST was. However, that would require simultaneous development of the spacecraft, the resupply vehicle and transfer interface. That would be costly; possibly justified but costly. It would be a daring space agency that proposed that in the current economic environment.If you want to add HST-style upgradability/repair capacity, that would cost even more and depend on SLS + a work platform or another large BLEO crew vehicle being available.
The ESA Space Weather Team is keen to maintain Herschel operational as long as possible because of the information that it provides on the radiation environment in Deep Space. Herschel will finish observing just as we reach solar maximum, so any time that it can spend after solar maximum will be a tremendous bonus, particularly if it could observe for a full solar cycle. For this, it does not matter of Herschel is in the Earth-Sun L2, the Earth-Moon L2, or in heliocentric orbit: the environment is similar and totally different to that in low-Earth orbit, where most satellites are, protected by the Earth’s magnetic field.
Quote from: Lar on 04/29/2013 09:46 pmSee: http://www.designntrend.com/articles/4051/20130429/herschel-telescope-european-space-agency-nasa-observatory.htmESA says the mission of Herschel is over after just 3 years, it has run out of liquid He to keep it cool and as it warms, it no longer can resolve things. Plans are to "pacify" it and then put it in a heliocentric parking orbit.1 Billion Euros... Has it taken all the pictures it possibly could take, or was there useful science it could have done ? How much would it cost to re"fuel" it, if we assumed a robust ISRU based infrastructure, and that it had been built to support refueling?It needs LHe and not propellant. LHe is not a ISRU commodity. Also, it is not an orbit conductive to servicing. Cheaper to launch an upgraded observatory.
See: http://www.designntrend.com/articles/4051/20130429/herschel-telescope-european-space-agency-nasa-observatory.htmESA says the mission of Herschel is over after just 3 years, it has run out of liquid He to keep it cool and as it warms, it no longer can resolve things. Plans are to "pacify" it and then put it in a heliocentric parking orbit.1 Billion Euros... Has it taken all the pictures it possibly could take, or was there useful science it could have done ? How much would it cost to re"fuel" it, if we assumed a robust ISRU based infrastructure, and that it had been built to support refueling?
The point *I* am making is that if we keep doing one off PROJECTS, where we drop a billion here, 2 billion there, 8 billion there, instead of putting effort into infrastructure first, we will NEVER get beyond throwaway spacecraft. Any given project doesn't have the budget for infrastructure. So we muddle along wastefully.
Now, do the numbers to develop a reusable infrastructure to bring humans plus a small spacestation to SEL1/2 bi yearly, then add the savings on the science missions and tell me if you save anything. I'm most interested on your discount factors and risk modelling. I'll read your paper very carefully, I promise.
Quote from: baldusi on 04/30/2013 09:42 pmNow, do the numbers to develop a reusable infrastructure to bring humans plus a small spacestation to SEL1/2 bi yearly, then add the savings on the science missions and tell me if you save anything. I'm most interested on your discount factors and risk modelling. I'll read your paper very carefully, I promise.RIght. You'll never develop a business case evaluating one mission. No single mission cuts it.Two engineers were asked to evaluate the business case for a new Hudson River crossing... seems it was suggested because all the current crossings stacked up bumper to bumper. They took a boat and went out in the middle of the river... then reported back. "No business case! We were out there all day, and not a single car crossed at that location"You guys are right. Let's just keep dumping billions into funding more Lewis and Clark expeditions, flags and footprints, etc... no business case for railroads.
Quote from: Ben the Space Brit on 04/30/2013 11:26 am@ Lar,The point Jim is making is that it is pointless talking about what might be available in the future as the spacecraft is unlikely to remain serviceable long enough for a servicing vehicle to be funded, designed, built and deployed. That's assuming that it is possible to service Herschel in space, which I bet isn't the case.There is an argument for designing future observatories to be upgradable and maintainable the way HST was. However, that would require simultaneous development of the spacecraft, the resupply vehicle and transfer interface. That would be costly; possibly justified but costly. It would be a daring space agency that proposed that in the current economic environment.If you want to add HST-style upgradability/repair capacity, that would cost even more and depend on SLS + a work platform or another large BLEO crew vehicle being available.The point *I* am making is that if we keep doing one off PROJECTS, where we drop a billion here, 2 billion there, 8 billion there, instead of putting effort into infrastructure first, we will NEVER get beyond throwaway spacecraft. Any given project doesn't have the budget for infrastructure. So we muddle along wastefully.Jim will never get that, I expect.
You guys are right. Let's just keep dumping billions into funding more Lewis and Clark expeditions, flags and footprints, etc... no business case for railroads.