Massive JPL Uranus/Neptune orbiter study

[_Augustus_]

http://www.lpi.usra.edu/icegiants/mission_study/Full-Report.pdf

It includes tons of technical/cost information, as well as designs for several different orbiters/probes.

Pretty much all of the designs use SEP, launch on DIVH/Atlas/Vulcan, and have a really long cruise time - I guess they don't think FH/NG will be available?

Edited June 14, 2017 by _Augustus_

[Streetwind]

It's not just about having a launcher available. NASA also needs the launcher certified.

There are multiple certification levels, though I'm not firm on the details. I think the Falcon 9 currently has level 2 out of 3 or something, while the Delta and Atlas series have level 3. So for the study, they probably limited themselves to flagship mission certified launchers (or a close relative, in case of the Vulcan).

Additionally, the launcher is less important than you think. This early study (done in anticipation of the ice giants likely being named a primary focus in the next Decadal Survey) is more about "how would the spacecraft be equipped" and "how much would it weigh" - the latter of which lets you estimate performance via almost any launch vehicle. When/if the mission actually becomes a thing, and you have a rough time frame and launch window, then you can start looking at every available launcher to pick the best options.

(EDIT: Ariane 5 might also have flagship level certification by now, considering NASA relies on it for their most expensive science payload ever. Still, I would be somewhat surprised if NASA ever selected it again in the future )

Edited June 14, 2017 by Streetwind

[_Augustus_]

1 hour ago, Streetwind said:

It's not just about having a launcher available. NASA also needs the launcher certified.

But won't FH/NG be certified by then?

[Streetwind]

To be fully honest, I want to see them fly first. Then we can take the next steps  

But my point was more "why bother spending time on alternative launch vehicles with unclear performance parameters when this study is so early, the mission isn't even guaranteed to be mandated yet".

[Steel]

1 hour ago, _Augustus_ said:

But won't FH/NG be certified by then?

Well it's not guaranteed, it could (although it's extraordinarily unlikely) be a massive disaster that never gets certified at all.

[Cristi]

@_Augustus_ thank you for this ! If you have more, please share

Edited June 14, 2017 by Cristi

[Racescort666]

Two things of note:

Quote

we note that launch vehicle performance may be different than currently assumed, and estimated costs depend on assumptions made about international participation and what components to include or exclude (e.g., launch vehicle)

And

Quote

It should be noted that the Falcon Heavy could also be considered in this timeframe, however data available to the team at the time of mission analysis indicated its performance for the missions considered would be in the same range as the Delta IV Heavy.

I think that they weren't looking at absolute performance of each launch vehicle but rather a ballpark of what type of vehicle they'd need for each mission. Also, under the cost summary, the launch vehicle is listed as having "Nuclear payload support" which may require SpaceX to make ground support changes. I don't know, I've never launched an RTG in real life.

Edited June 14, 2017 by Racescort666
clarity

[magnemoe]

28 minutes ago, Racescort666 said:

I think that they weren't looking at absolute performance of each launch vehicle but rather a ballpark of what type of vehicle they'd need for each mission. Also, under the cost summary, the launch vehicle is listed as having "Nuclear payload support" which may require SpaceX to make ground support changes. I don't know, I've never launched an RTG in real life.

You have not launched an RTG in real life? 
Guys we have an noob here

[Starman4308]

I think the long cruise time can be explained by the fact that the ice giants are all really, really, really far from Earth. A standard Hohmann transfer to Uranus takes 16 years, to Neptune 30 years. That's a pretty significant fraction of the expected lifespan of an RTG; it's no wonder they're looking at ways to cut down the transfer time.

What I've found interesting so far scanning this article is that there's plans to use aerobraking at the ice giants, using a cutting-edge heat shield to not fry the probe on the way through. It could certainly save a lot of mass; out at the ice giants, you can forget about using solar-powered ion engines to slow down, and chemical engines are... chemical engines.

[Kryten]

10 hours ago, Streetwind said:

(EDIT: Ariane 5 might also have flagship level certification by now, considering NASA relies on it for their most expensive science payload ever. Still, I would be somewhat surprised if NASA ever selected it again in the future )

US missions are required to fly on US launchers: Webb is a US-led international mission, not a US mission. AFAIK no US planetary mission has been a formal international mission.

 

2 hours ago, Racescort666 said:

Also, under the cost summary, the launch vehicle is listed as having "Nuclear payload support" which may require SpaceX to make ground support changes. I don't know, I've never launched an RTG in real life.

RTG's require both specialised GSE and vehicle mods (mostly to the payload fairing) and a specialised form of LV certification, tougher than the standard level 3 cert. Currently only atlas is nuclear-rated.

[Racescort666]

13 hours ago, Kryten said:

RTG's require both specialised GSE and vehicle mods (mostly to the payload fairing) and a specialised form of LV certification, tougher than the standard level 3 cert. Currently only atlas is nuclear-rated.

That's kind of what I figured but I didn't want to speculate in too much detail.

[DerekL1963]

From the Launch Vehicle Options section of the Mission Design appendix:  (Links added by me to link directly to the relevant performance data - especially as the FH's has changed over time.)  "It should be noted that the Falcon Heavy could also be considered in this timeframe, however data available to the team at the time of mission analysis indicated its performance for the missions considered would be in the same range as the Delta IV Heavy".

[Starman4308]

I've finished reading the report. A few things jump out at me.

First, these missions would be so easy to afford were NASA not constrained to waste billions of dollars annually for the Senate Launch System and the Multi-Purposeless Crew Vehicle. A couple years of the SLS budget, and we could launch full payload missions to both ice giants on DIVH, Falcon Heavy, or New Glenn boosters.

I'm thoroughly of the opinion that NASA should focus on building spacecraft and operating the ISS and it's successor, not launch vehicles. I really don't think we'll put astronauts on Mars anytime soon; the challenges are immense, and the scientific payback not hugely greater than vastly cheaper unmanned missions.

Back to the ice giant mission proposal: if the poorly characterized nature of their atmospheres makes aerocapture dangerous, well... they'll be a lot better characterized when we send a second mission to these planets. That might not be for decades after the first mission, but we'll have a mass efficient method to capture into Uranus/Neptune orbit.

It's curious how solar electric propulsion mostly just makes these missions more problematic and expensive. The more time we try to save in transit, the more costly orbital insertion becomes, which almost has to be done on MMH/NTO, as ion propulsion requires more RTGs than is practical, and cryogenic chemical/nuclear is not well proven or developed for long duration missions.

If we understood their atmospheres better, I'd be strongly tempted to suggest an SEP with aerocapture profile, but with conventional MMH/NTO being the most practical capture method, we really need a fairly long coast phase so we don't just blow straight past these planets, and that is achievable via slingshots and chemical propulsion.