Author Topic: Missions to the Ice Giants Uranus and Neptune  (Read 342325 times)

Offline Star One

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Missions to the Ice Giants Uranus and Neptune
« Reply #20 on: 02/13/2014 03:00 pm »
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.

Does that mean that within any kind of reasonable timescale we will likely not see a launcher capable of placing a craft on a direct flight to Neptune?
« Last Edit: 02/13/2014 03:00 pm by Star One »

Offline vjkane

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #21 on: 02/13/2014 08:37 pm »
My opening caveat: I am skeptical of all science missions that propose using SLS. The cost is prohibitive.
If I remember correctly, an SLS launch would be (note the conditional) ~$1B.  By taking your time to get there, you can almost afford a New Frontiers mission for the launch vehicle cost difference.

Offline metaphor

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #22 on: 02/13/2014 09:06 pm »
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.

Does that mean that within any kind of reasonable timescale we will likely not see a launcher capable of placing a craft on a direct flight to Neptune?

It's not that much harder to go straight to Neptune rather than Jupiter (about 2 km/s of extra delta-v from Earth orbit).  But when you attempt really high delta-v's with a single stage, the empty mass of that stage becomes the majority of the throw mass instead of the actual payload.  Rather than squeezing out an extra 2 km/s delta-v from the upper stage, it would be more efficient to add an extra stage on top, which for 2 km/s means about a 2:1 mass ratio.  So if a rocket like the SLS can throw 8 tons straight to Jupiter, with the addition of another 4-ton stage it could throw a 4-ton payload straight to Neptune.

By the way, these proposals for missions to Uranus and Neptune are really interesting.  Are there any conventional missions to Uranus rather than Neptune using aerocapture?
« Last Edit: 02/13/2014 09:08 pm by metaphor »

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #23 on: 02/13/2014 10:19 pm »
By the way, these proposals for missions to Uranus and Neptune are really interesting.  Are there any conventional missions to Uranus rather than Neptune using aerocapture?

Define "conventional."

I still have not posted the decadal survey Uranus mission study. That's the most conventional mission proposed. (I think it's in the Uranus Pathfinder slides I posted earlier.) Does not use aerocapture.

Aerocapture is more severe than aerobraking. It should not be hard to do for Titan. It gets more extreme for Neptune in particular. You can Google "Neptune aerocapture" and get a few good docs like this:

http://archive.org/stream/nasa_techdoc_20060012092/20060012092_djvu.txt


Offline metaphor

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #24 on: 02/14/2014 02:29 am »
By the way, these proposals for missions to Uranus and Neptune are really interesting.  Are there any conventional missions to Uranus rather than Neptune using aerocapture?

Define "conventional."

I still have not posted the decadal survey Uranus mission study. That's the most conventional mission proposed. (I think it's in the Uranus Pathfinder slides I posted earlier.) Does not use aerocapture.

Aerocapture is more severe than aerobraking. It should not be hard to do for Titan. It gets more extreme for Neptune in particular. You can Google "Neptune aerocapture" and get a few good docs like this:

http://archive.org/stream/nasa_techdoc_20060012092/20060012092_djvu.txt

I was just wondering if there was a Uranus equivalent to this mission you posted:

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.

By conventional I just meant not using NEP.  I was thinking Uranus might be an easier target than Neptune since it's closer and takes less delta-v or trip time, and aerocapture might be easier in Uranus's atmosphere due to its larger scale height.

Also, is there a reason why all the probes are encountering the planet's atmosphere at such high entry angles?  Is the 400 g's of peak deceleration less of a design constraint than getting deep in the atmosphere faster?
« Last Edit: 02/14/2014 02:38 am by metaphor »

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #25 on: 02/14/2014 02:48 am »
By conventional I just meant not using NEP.  I was thinking Uranus might be an easier target than Neptune since it's closer and takes less delta-v or trip time, and aerocapture might be easier in Uranus's atmosphere due to its larger scale height.

I think they all need a propulsion stage (note the the study done for the decadal survey was a solar electric propulsion, SEP, stage, not NEP, which hasn't been done before). And I don't think aerocapture is necessary at Uranus. I got the attached studies from here:

http://sites.nationalacademies.org/SSB/SSB_059331

« Last Edit: 02/14/2014 02:52 am by Blackstar »

Online Hobbes-22

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #26 on: 02/17/2014 07:13 pm »
A team based mostly at the Italian institute for Space Astrophysics and Planetoloty has proposed a mission named ODINUS (Origins, Dynamics and Interiors of Neptunian and Uranian Systems). This is an attempt to fit orbital missions to both planets into one ESA L-class mission.

http://odinus.iaps.inaf.it/

http://arxiv.org/abs/1402.2650

Quote
In order to fit the budget of an L-class mission, a conservative, straw-man configuration for the ODINUS mission could be based on two New Horizons-like spacecraft, i.e.:

    about 6 instruments in the scientific payload + radio science;
    about 500-600 kg of dry mass for each spacecraft;
    hybrid (ionic and chemical) propulsion;
    radioisotope-powered energy source.

The limitations on the scientific payload and the dry mass of the spacecraft come from a worst-case scenario evaluation of the fuel budget needed to reach the ice giants and to insert them on planetocentric orbits. If we consider the Hohmann transfer orbit between Earth and Uranus (or Neptune) with an orbital insertion at about 2x10^7 km from the relevant planet on a highly eccentric orbit, the required Δv of about 5 km/s translates into a wet-to-dry mass ratio of about 5 for each spacecraft. This implies that 600 kg of dry mass requires a wet mass at launch of about 3000 kg. Such a wet mass at launch would make the mission feasible either considering a single launch of the Freyr and Freyja spacecrafts with an Ariane V rocket or two separate launches with Soyuz rockets. The scenario contemplating two separate launches allows the two trajectories to be optimized independently, thus allowing for the largest savings of either fuel or travel time, but a preliminary check of the orbital positions of Uranus and Neptune showed that the two ice giants will be in a favorable position to launch the two spacecraft together and then separate their paths at Uranus.

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #27 on: 02/17/2014 07:57 pm »
I thought I had mentioned ODINUS, either here or somewhere else. Must have forgotten. I need to figure out how ODINUS relates to Uranus Pathfinder.

Offline vjkane

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #28 on: 02/17/2014 11:45 pm »
I thought I had mentioned ODINUS, either here or somewhere else. Must have forgotten. I need to figure out how ODINUS relates to Uranus Pathfinder.
I believe this was two separate groups.  The ODINUS spacecraft were simpler and (as I recall) did not include atmospheric probes.

Offline EE Scott

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #29 on: 02/18/2014 12:06 am »
This thread is the most fun thread I've read in a long time.  Great stuff here!  Thanks for the content, Blackstar.  I have hoped for icy giants missions for a long time, so much fascinating data just waiting to blow our minds.
Scott

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #30 on: 02/18/2014 01:35 am »
I thought I had mentioned ODINUS, either here or somewhere else. Must have forgotten. I need to figure out how ODINUS relates to Uranus Pathfinder.
I believe this was two separate groups.  The ODINUS spacecraft were simpler and (as I recall) did not include atmospheric probes.

I haven't looked at them closely yet, but I think that the ODINUS proposal is for two identical spacecraft, one to Uranus and one to Neptune. I'm not quite sure how one could pull that off, because the travel times are going to be different.

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #31 on: 02/18/2014 01:38 am »
This thread is the most fun thread I've read in a long time.  Great stuff here!  Thanks for the content, Blackstar.  I have hoped for icy giants missions for a long time, so much fascinating data just waiting to blow our minds.

I think I linked to the Decadal Survey mission studies site earlier on. Go there and download all the mission studies.

I'm also working on an article on Europa mission proposals, but haven't collected as many of those yet. And I have an article in the works on Mercury mission proposals, but I think I only have most of those in paper form and will have to scan them.

If anybody else wants to start threads on other planetary mission studies, be my guest. In the past I wanted to do an article on Phobos/Deimos mission proposals, which include a number of human mission studies. I haven't gotten to that.

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #32 on: 02/25/2014 04:22 pm »
http://www.hou.usra.edu/meetings/icegiants2014/

Save the Date!
Workshop on the Study of the Ice Giant Planets

July 28–30, 2014
Johns Hopkins Applied Physics Laboratory, Laurel, Maryland

The goal of this 2.5-day workshop is to raise awareness of the uniqueness/importance of ice giants in our solar system and others and lay out key science goals and a potential suite of investigations for New Frontiers-Flagship mission concepts. We will review the current state of knowledge of all aspects of the ice giant planetary systems (planets, satellites, rings, etc.), and how it relates to our knowledge of the gas giants, planetary formation models, and the study of exoplanets, incorporating outcomes of the 2013 Paris Uranus meeting. We will initiate a major effort to prioritize the science goals of future Uranus and Neptune missions and review studied architectures for these mission concepts. Contributed talks/posters are welcome, particularly those that focus on the state of knowledge and mission studies. Abstract submission will open in early May 2014.


Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #33 on: 02/25/2014 08:55 pm »
OPAG Updates, February 25, 2014

Dear Colleagues,

We had a very successful meeting January 13–14 in Tucson, Arizona.  The report and findings are now posted on the OPAG homepage http://www.lpi.usra.edu/opag/

Please mark your calendars for the next OPAG meeting, to be held July 23–24 in the DC area. 

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #34 on: 03/25/2014 08:38 pm »
Neptune is my favorite planet and Triton is my favorite moon. Thanks for asking that.

Here are relevant chapters from the definitive reference book on these two objects.
« Last Edit: 03/25/2014 10:28 pm by Blackstar »

Offline truth is life

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #35 on: 04/04/2014 12:51 am »
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.
There definitely were. I have several papers from as early as 1966 that considered orbital missions to Neptune and Uranus, from Astro Sciences Center, that is the Illinois Institute of Technology. Additionally, I have several documents dating from as early as 1973 describing a Saturn/Uranus probe mission based on Pioneer hardware instead of Voyager hardware, with what seem to me to be fairly developed design details. So they were definitely looking into ice giants mission at those dates. I will upload them to this thread, just give me a minute (they're all stored on a different computer than the one I'm writing this post on).

Generally, whenever I've tried to look into it it seems that people began studying, if only at a superficial level, missions to every destination imaginable as soon as space launch was available.

Offline truth is life

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #36 on: 04/04/2014 12:53 am »
Okay, Astro Sciences Center, "A Survey of Missions to Jupiter, Saturn, Uranus, Neptune, and Pluto," 1966

Offline truth is life

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #37 on: 04/04/2014 12:55 am »
Astro Sciences Center again, "A Preliminary Study of Composite Orbiter/Lander Missions to Satellites of the Outer Planets" (they specifically study Triton), 1970

Offline truth is life

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #38 on: 04/04/2014 01:03 am »
Everything I have on Saturn/Uranus atmospheric probe proposals for Pioneer and Mariner-derived systems.

Offline Blackstar

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Re: Missions to the Ice Giants Uranus and Neptune
« Reply #39 on: 04/05/2014 12:32 am »
Graphics from one of the above reports illustrating a landing on a moon (Triton). Given the technology of the day, this was a very ambitious idea.

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