Quote from: sdsds on 07/29/2014 10:05 pmSorry for asking a rather basic question but: could the "$1 billion" Europa missions be designed (like Clipper) to take either a VEEGA trajectory after launch on Atlas or a direct trajectory after launch on SLS? Or is there something about $1b that makes that not possible? Er, this is a weird question. No matter what the cost of the mission, it still has to get to Europa. So it's either going to launch on an Atlas or an SLS. Now some people argue that taking a VEEGA trajectory is going to cost more in operations costs than a direct trajectory, because you have to spend $X per year and it is more years to go that way than directly. So maybe you save $80 million in operating costs with the direct trajectory vs. the VEEGA trajectory (but do you pay more for the launch vehicle?).
Sorry for asking a rather basic question but: could the "$1 billion" Europa missions be designed (like Clipper) to take either a VEEGA trajectory after launch on Atlas or a direct trajectory after launch on SLS? Or is there something about $1b that makes that not possible?
Quote from: Blackstar on 07/30/2014 03:52 amQuote from: sdsds on 07/29/2014 10:05 pmSorry for asking a rather basic question but: could the "$1 billion" Europa missions be designed (like Clipper) to take either a VEEGA trajectory after launch on Atlas or a direct trajectory after launch on SLS? Or is there something about $1b that makes that not possible? Er, this is a weird question. No matter what the cost of the mission, it still has to get to Europa. So it's either going to launch on an Atlas or an SLS. Now some people argue that taking a VEEGA trajectory is going to cost more in operations costs than a direct trajectory, because you have to spend $X per year and it is more years to go that way than directly. So maybe you save $80 million in operating costs with the direct trajectory vs. the VEEGA trajectory (but do you pay more for the launch vehicle?).Is there also an additional cost due to the thermal insulation needed because of the higher temperatures at Venus? I seem to remember that being an advantage of a straight-to-Jupiter trajectory.
Quote from: Star One on 07/28/2014 03:07 pmEuropa Clipper Would Wash Out Other Nuclear-powered Missions.SpaceNews generally writes does very good reporting, and this article is except for one omission. The Clipper mission can also be done (based on current engineering assessments) with solar panels. There are various engineering and budget trades (solar panels are heavier and must always point toward the sun; but the solar option is cheaper than the Pu-238 option). So far as I know, there's been no decision on which direction to go.If the Clipper doesn't use Pu-238, then NASA could make MMRTGs available to Discovery and New Horizon missions. There are a number of concepts that either depend on a plutonium power supply or would benefit from it.
Europa Clipper Would Wash Out Other Nuclear-powered Missions.
Quote from: vjkane on 07/30/2014 04:43 amQuote from: Star One on 07/28/2014 03:07 pmEuropa Clipper Would Wash Out Other Nuclear-powered Missions.SpaceNews generally writes does very good reporting, and this article is except for one omission. The Clipper mission can also be done (based on current engineering assessments) with solar panels. There are various engineering and budget trades (solar panels are heavier and must always point toward the sun; but the solar option is cheaper than the Pu-238 option). So far as I know, there's been no decision on which direction to go.If the Clipper doesn't use Pu-238, then NASA could make MMRTGs available to Discovery and New Horizon missions. There are a number of concepts that either depend on a plutonium power supply or would benefit from it.There's also a hybrid solar/RTG option that was going to be evaluated as of a few months ago. But RTGs are the lowest risk option. I suspect that for an expensive mission they will want the lowest risk option.
If they go with SLS, RTG also mean nuclear-rating it.
If solar panels are safe enough to risk for the $8 billion JWSC and Hubble, they are probably okay for a measly $1 - $2 billion mission.
I would think the hybrid option would be pretty competitive on risk. You can get just enough RTGs to support a baseline science level, so that even if the solar completely disappeared you could get most of the science done. And, truth is, solar panels aren't too shabby in reliability themselves. If solar panels are safe enough to risk for the $8 billion JWSC and Hubble, they are probably okay for a measly $1 - $2 billion mission.But the hybrid option would carry all the complication, cost, size, and weight of both the RTGs and solar and then some. Maybe not a problem if you are launching on SLS and you don't have the money to fill the size/weight envelope with instruments, but could be trouble for an Atlas. Still, it might be worth it, IF it enables another small mission or two to take place (meaning there is some assurance the RTG capability wouldn't just sit unused for the entire time frame).It will be interesting, once Falcon Heavy gets going, to see what its payload/C3 graph looks like.
It will be interesting, once Falcon Heavy gets going, to see what its payload/C3 graph looks like.
Quote from: metaphor on 07/30/2014 03:18 pmQuote from: Blackstar on 07/30/2014 03:52 amQuote from: sdsds on 07/29/2014 10:05 pmSorry for asking a rather basic question but: could the "$1 billion" Europa missions be designed (like Clipper) to take either a VEEGA trajectory after launch on Atlas or a direct trajectory after launch on SLS? Or is there something about $1b that makes that not possible? Er, this is a weird question. No matter what the cost of the mission, it still has to get to Europa. So it's either going to launch on an Atlas or an SLS. Now some people argue that taking a VEEGA trajectory is going to cost more in operations costs than a direct trajectory, because you have to spend $X per year and it is more years to go that way than directly. So maybe you save $80 million in operating costs with the direct trajectory vs. the VEEGA trajectory (but do you pay more for the launch vehicle?).Is there also an additional cost due to the thermal insulation needed because of the higher temperatures at Venus? I seem to remember that being an advantage of a straight-to-Jupiter trajectory.I've heard something about that too, but I suspect that it's not a big cost. Really, it's just insulation (plus the engineering evaluation). Shouldn't cost much.
Quote from: Blackstar on 07/30/2014 04:44 pmQuote from: metaphor on 07/30/2014 03:18 pmQuote from: Blackstar on 07/30/2014 03:52 amQuote from: sdsds on 07/29/2014 10:05 pmSorry for asking a rather basic question but: could the "$1 billion" Europa missions be designed (like Clipper) to take either a VEEGA trajectory after launch on Atlas or a direct trajectory after launch on SLS? Or is there something about $1b that makes that not possible? Er, this is a weird question. No matter what the cost of the mission, it still has to get to Europa. So it's either going to launch on an Atlas or an SLS. Now some people argue that taking a VEEGA trajectory is going to cost more in operations costs than a direct trajectory, because you have to spend $X per year and it is more years to go that way than directly. So maybe you save $80 million in operating costs with the direct trajectory vs. the VEEGA trajectory (but do you pay more for the launch vehicle?).Is there also an additional cost due to the thermal insulation needed because of the higher temperatures at Venus? I seem to remember that being an advantage of a straight-to-Jupiter trajectory.I've heard something about that too, but I suspect that it's not a big cost. Really, it's just insulation (plus the engineering evaluation). Shouldn't cost much.That's a pretty wild statement. How do you know it would just need "extra insulation" ? It depends a lot on the spacecraft design. Maybe it's just insulation? Maybe it will need a new attitude "BBQ-like" mode? Maybe it will need active thermal control? As for the cost of engineering evaluation, it is one of the main reason all these missions cost billions.
if you put 100 Europa scientists into a room and told them they could vote for either Atlas or SLS, you would probably get 99 people voting for Atlas.
I understand why today's researchers are the population one would first think to poll.
Quote from: a_langwich on 07/30/2014 06:49 pmI would think the hybrid option would be pretty competitive on risk. You can get just enough RTGs to support a baseline science level, so that even if the solar completely disappeared you could get most of the science done. And, truth is, solar panels aren't too shabby in reliability themselves. If solar panels are safe enough to risk for the $8 billion JWSC and Hubble, they are probably okay for a measly $1 - $2 billion mission.But the hybrid option would carry all the complication, cost, size, and weight of both the RTGs and solar and then some. Maybe not a problem if you are launching on SLS and you don't have the money to fill the size/weight envelope with instruments, but could be trouble for an Atlas. Still, it might be worth it, IF it enables another small mission or two to take place (meaning there is some assurance the RTG capability wouldn't just sit unused for the entire time frame).It will be interesting, once Falcon Heavy gets going, to see what its payload/C3 graph looks like. I don't think they would count risk in this case as "solar plus RTG." Instead, the risk comes in integrating those two technologies. That might seem easy to us, who don't know anything about doing it, but I would note that it has not been done before. There could be all kinds of complications that come from running two different power supplies into the bus.My impression, and I've said this before, is that if you put 100 Europa scientists into a room and told them they could vote for either Atlas or SLS, you would probably get 99 people voting for Atlas. SLS comes with all kinds of unknown and murky political and budgetary risks. Better to go with the known quantity, which is Atlas. So I think that the hybrid RTG/solar option is being evaluated for Atlas, because that's what most of the Europa scientists and engineers believe is the most likely launch vehicle.
But as the departure dates get closer the calculus might change.
In any case, the notion that a mission in development can "maintain dual launch capability through CDR" seems in the current political reality to mandate that it do so.
Quote from: sdsds on 07/31/2014 03:22 amBut as the departure dates get closer the calculus might change. Well, sure, because "future risk" is being retired. By 2021, if all goes well, SLS will have flights under its belt.
There's no internal equivalent to an insurance or warranty?