Quote from: Ben the Space Brit on 02/13/2014 12:42 pmOne 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.
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.
Quote from: Blackstar on 02/13/2014 02:31 pmQuote from: Ben the Space Brit on 02/13/2014 12:42 pmOne 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?
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?
Quote from: metaphor on 02/13/2014 09:06 pmBy 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
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.
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.
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.
Quote from: Blackstar on 02/17/2014 07:57 pmI 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.
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.
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.