Missions to the Ice Giants Uranus and Neptune

Missions to the Ice Giants Uranus and Neptune by Blackstar on 08 Feb, 2014 17:04
I thought I would start a thread for posting mission proposals for Ice Giants missions. I've got a number of these and will start posting them here.
#1 by Blackstar on 08 Feb, 2014 17:05
Here is a recent Uranus mission proposal. This is Uranus Pathfinder, a European proposal.

UranusPathfinderMission.pdf
#2 by Blackstar on 08 Feb, 2014 17:07
Here are the presentation slides for the Uranus Pathfinder mission.

uranuspathfinder_v0.pdf
#3 by Star One on 08 Feb, 2014 20:53
Thanks for posting those up some interesting reading. Just shame we aren't going to see any reality in these kind of missions for a long, long time I would imagine.
#4 by kevin-rf on 09 Feb, 2014 18:31
Can I quibble with the second slide, 99% of the solar system's mass is in the Gas Giants... Only if you include the sun as a gas giant and not a star!

Sounds interesting none the less...
#5 by Comga on 09 Feb, 2014 20:52
Quote from: Blackstar on 08 Feb, 2014 17:07
Here are the presentation slides for the Uranus Pathfinder mission.

Cool

But... Three Americium ASRGs? Given that NASA recently gave up on ASRGs powered by "the usual" Plutonium that seems pretty far fetched.

My recollection is that Alan Stern proposed a replica New Horizons II for a Neptune fly-by like the Pluto fly-by coming up in a year for New Horizons. Never stood a chance.

Could also look up the NEP "proposals" from a few years ago. These involved using ASRGs to power ion engines to rendezvous with the outer planets on long, looping, constant acceleration trajectories. Google turns up several including this one by Russian and Brazilian authors. Some like this one talk about 95 kW, which doesn't seem realistic. This one is by NASA authors.

Wouldn't it be grand to build a fleet of these to orbit both Neptune and Uranus, and maybe a dwarf planet? Given that so much of the cost is NRE for the spacecraft, it would seem to make sense (in a universe where Congress and the NASA Administrator have ruled out Flagship missions) but how would one propose it? While it would be efficient overall the going-in price would be prohibitive, even if there was a budget.
#6 by baldusi on 10 Feb, 2014 15:49
Have you considered DSN and support staff costs? Icy Planets and beyond mean loooong travel times, and those years of support add up fast. Not to mention that a NEP would need constant oversight.
#7 by jebbo on 11 Feb, 2014 07:39
On the development of European RTGs, etc here is a presentation from Feb 2012. Slide 7 shows the roadmap.

Even with slips, this seems feasible for a post-2024 launch (as it hasn't been selected for M3).

--- Tony

tech-18E.pdf
#8 by Blackstar on 11 Feb, 2014 19:01
Here is another one. This is one of two NASA "Vision Mission" studies concerning Neptune that were done in 2005. This one was based upon the Prometheus technology.

Volume 1-Neptune Orbiter with Probes - Final Report.pdf
#9 by Blackstar on 11 Feb, 2014 19:02
Here is the slide presentation for the "Neptune Orbiter With Probes" Vision Mission study. This one was based on the Prometheus technology.

NepOrbWProbesPrometheus.pdf
#10 by Blackstar on 11 Feb, 2014 19:05
You probably won't find these ones too interesting. This is the initial JPL "Team X" Vision Mission study for a Neptune Orbiter With Probes. This one was NOT based on Prometheus. I have a more interesting report that followed this.

Neptune_TmX_1.pdf

Neptune_TmX_2.pdf
#11 by Blackstar on 11 Feb, 2014 19:07
This is the formal study that followed the JPL Team X study. This was done in 2005 as part of the Vision Mission studies. This is actually my favorite outer planets mission, because I love the idea of doing aerocapture into Neptune's atmosphere--i.e. using the vehicle to actually brake itself all the way into orbit.

I have presentation slides for this somewhere and will post them too.

Neptune_5_02_06.pdf
#12 by Blackstar on 11 Feb, 2014 19:12
This is the earliest outer planets study that I know of. It was done in 1974 by JPL and was a proposal to do a dedicated Uranus flyby with an atmospheric probe. This was essentially a follow-on to Voyager.

It is possible that some limited studies were done of outer planet missions in the 1960s. I have seen an artist illustration of a nuclear reactor powered spacecraft that may have been dedicated to Saturn, and possibly farther out, and it dated from around 1966 or so. And of course the availability of the Saturn V in the latter 1960s caused some people to consider using it for planetary missions. The only approved mission was Voyager-Mars, which got canceled, but it seems conceivable that somebody proposed using the Saturn V for other planetary missions.

MarinerJupiter-Uranus1979.pdf
#13 by Blackstar on 12 Feb, 2014 15:08
There is an entry for the New Horizons 2 proposal here:

http://en.wikipedia.org/wiki/New_Horizons_2

NH2 was a proposal for a second mission to a Kuiper Belt Object. Essentially it would be a backup for New Horizons. But it would fly past Uranus on its way to the KBO. I have attached the short NH2 proposal. Also attached is the external assessment of NH2 done in March 2005. The latter report quite clearly stated that NH2 could not be done because there was no additional RTG available for the mission by the launch deadline. But it also pretty clearly stated that the mission was a bad idea. The politics behind this is rather interesting, and if you compare it to what happened with Mars 2020 in 2012 you will see a lot of parallels.

new_horizons2.pdf

nh2_final_report.pdf
#14 by Robotbeat on 12 Feb, 2014 21:37
From what I understand, NASA hasn't abandoned ASRG. It's just not on the fast-track for introduction to an operational system. Like many projects at NASA, there are still funding streams for some work on it, and work will continue on the back-burner. Important projects like ASRG that are critical enabling technologies often go through lapses and rebirths like this, so just have patience. I mean, I still think it's a rotten idea to waste 2/3 of our Plutonium 238 this way while also increasing weight slightly and reducing power available for deep space missions, but it's not like the decision is irreversible.
#15 by simonbp on 13 Feb, 2014 04:42
Quote from: Blackstar on 12 Feb, 2014 15:08
There is an entry for the New Horizons 2 proposal here:

http://en.wikipedia.org/wiki/New_Horizons_2

NH2 was a proposal for a second mission to a Kuiper Belt Object. Essentially it would be a backup for New Horizons. But it would fly past Uranus on its way to the KBO. I have attached the short NH2 proposal. Also attached is the external assessment of NH2 done in March 2005. The latter report quite clearly stated that NH2 could not be done because there was no additional RTG available for the mission by the launch deadline. But it also pretty clearly stated that the mission was a bad idea. The politics behind this is rather interesting, and if you compare it to what happened with Mars 2020 in 2012 you will see a lot of parallels.

Which is an especially interesting "what-if", because the nominal target was 1999 TC36. At the time it was thought to just be a wide binary system, but subsequent imaging has shown that it is actually a hierarchical triple system, with a tight inner pair and a third body on an eccentric orbit that rapidly precesses. It's one of the wackiest minor planet systems in the solar system.

WRT to power at Uranus, unconcentrated solar would be really hard (there are a lot of quantum inefficiencies at those light levels), but a concentrated array like Boeing's FAST might actually work. I remember asking someone at Boeing about just this at DPS last year, and they were confident about being able to do it Saturn, but waffled about Uranus. So, it's not impossible (especially on a 10-year time frame), but it will take more work to get there.
#16 by Blackstar on 13 Feb, 2014 11:51
Quote from: Robotbeat on 12 Feb, 2014 21:37
From what I understand, NASA hasn't abandoned ASRG. It's just not on the fast-track for introduction to an operational system. Like many projects at NASA, there are still funding streams for some work on it, and work will continue on the back-burner.

ASRG is not canceled, but there is no work going on with it (or if there is, that work is being ended soon). Here are a couple of recent presentations on it.

I cannot remember if anybody has publicly stated the estimated cost to complete the ASRG, but NASA's planetary budget situation will have to improve in order to make it possible.

5_mcnutt.pdf

1119-1130-Dudzinski.pdf
#17 by Blackstar on 13 Feb, 2014 12:04
Quote from: simonbp on 13 Feb, 2014 04:42
Which is an especially interesting "what-if", because the nominal target was 1999 TC36. At the time it was thought to just be a wide binary system, but subsequent imaging has shown that it is actually a hierarchical triple system, with a tight inner pair and a third body on an eccentric orbit that rapidly precesses. It's one of the wackiest minor planet systems in the solar system.

The history of that mission is interesting and I'll go into it briefly in the article on the history of ice giants missions that I'm writing. Essentially, the NH team proposed that they could build a second spacecraft as backup to their first, and justified it in terms of previous planetary missions having backups. It would not surprise me if they were inspired by MER.

The problem was that this would cost money, and that money would have to come from somewhere, most likely a Discovery mission competition. And that meant that the NH team would get to build two things, and everybody else who was proposing to build a mission was out of luck. Not exactly fair. In addition, the decadal survey never said anything about a backup even though the NH people tried to discern god's intent in the words in the decadal survey and use them to justify them getting a second mission.

Now anybody can propose anything they want. But the PI for the NH mission went up to Capitol Hill and lobbied for NH2 and that's the kind of end-run around the mission selection process that earns people enemies. In the end, the Senate Appropriations Committee called for an independent review of the NH2 proposal (that document is linked on Wikipedia and I attached it above). I don't know if the NH2 team argued for that review, or if that was Congress' way of getting additional information--it is common for Congress, when faced with NASA saying one thing and a group of loud people saying something else, to call for an independent review. So the independent review team stood up, rapidly held some meetings, and issued their report in March 2005. The short report is worth skimming, because one of the first things it does is bust the claim that NH2 would be cheap. It actually would not cost much less than NH1. And the review team also said something that was rather amusing, which is that if NASA was going to do an NH2 mission, they should compete it, meaning that the NH team should not simply be given more money to do it (which is what they wanted). Of course, a competition would add time, but already there was no way to meet the launch window.
#18 by Ben the Space Brit on 13 Feb, 2014 12:42
One of the problems with extreme outer solar-system missions is the necessity (when launched with EELVs) to make multiple passes of other planets to build up velocity. In one of the papers referred to in the thread, it was mentioned that a conventionally-launched Uranus probe would be loaded down with heavy thermal protection for a Venus fly-by.

Could this be a useful application of SLS? How much could SLS with the as-planned DUUS throw through a direct TJI or TSI to slingshot towards Uranus?
#19 by Blackstar on 13 Feb, 2014 14:31
Quote from: Ben the Space Brit on 13 Feb, 2014 12:42
One of the problems with extreme outer solar-system missions is the necessity (when launched with EELVs) to make multiple passes of other planets to build up velocity. In one of the papers referred to in the thread, it was mentioned that a conventionally-launched Uranus probe would be loaded down with heavy thermal protection for a Venus fly-by.

Could this be a useful application of SLS? How much could SLS with the as-planned DUUS throw through a direct TJI or TSI to slingshot towards Uranus?

My opening caveat: I am skeptical of all science missions that propose using SLS. The cost is prohibitive.

That said, one of the potential advantages of SLS for planetary missions is that it can eliminate gravity assist trajectories. This can have many benefits. Off the top of my head:

-eliminates need for unnecessary mass, like thermal protection for Venus flybys
-reduces time to reach destination
-eliminates flybys of Earth with RTGs (a safety concern)
-could reduce overall mission lifetime required testing (for instance, the spacecraft only has to be certified to operate for 8 years instead of 14 I think that the last one could be interesting for somebody to explore.)

There are C3 (throw-weight/energy) charts for outer planets missions using SLS. I think I posted some of them in another thread. They are for direct missions to the destinations and show how much mass you can throw directly to Europa, Saturn, and Uranus. For Uranus even with SLS (and I think even with SLS Block II) the line still falls off the graph, meaning that you still cannot do a direct mission to Uranus. However, I'm not sure that's a concern, since I presume that most outer planets missions are going to swing past Jupiter. However, however, Jupiter isn't always in the right position, so that eliminates your opportunities. The point of a direct mission is that you can launch pretty much whenever you want to, or at least during a lot more windows.

Somebody at JPL probably has a nice little computer program that does all of this stuff, telling them the available launch windows for a whole bunch of mission options and allowing them to alter payload, time, etc.