Author Topic: Pluto Orbital Mission  (Read 5029 times)

Offline Star One

  • Senior Member
  • *****
  • Posts: 7512
  • UK
  • Liked: 1204
  • Likes Given: 168
Pluto Orbital Mission
« on: 10/19/2016 05:34 PM »
A few very initial details from Alan Stern of a study into this.

Quote
Several times during the briefing, Stern indicated how having a future mission that orbited Pluto would answer so many outstanding questions the team has. He outlined one potential mission that is in the very earliest stages of study where a spacecraft could be launched on NASA’s upcoming Space Launch System (SLS) and the spacecraft could have an RTG-powered ion engine that would allow a fast-moving spacecraft the ability to slow down and go into orbit (unlike New Horizons). This type of architecture would allow for a flight time of 7.5 years to Pluto, quicker than New Horizons’ nearly 9.5 years.

http://www.universetoday.com/131492/latest-results-new-horizons-clouds-pluto-landslides-charon/

Online Phillip Clark

  • Full Member
  • ****
  • Posts: 1947
  • Hastings, England
  • Liked: 244
  • Likes Given: 574
Re: Pluto Orbital Mission
« Reply #1 on: 10/19/2016 05:42 PM »
There would be some serious orbital perturbations from Charon - could a Pluto orbiter manage those?

Online Orbiter

  • Senior Member
  • *****
  • Posts: 2168
  • Florida
  • Liked: 371
  • Likes Given: 905
Re: Pluto Orbital Mission
« Reply #2 on: 10/19/2016 05:45 PM »
There would be some serious orbital perturbations from Charon - could a Pluto orbiter manage those?

Sure, just orbit around the Pluto-Charon barycenter like Hydra, Nix, Kerberos, and Styx do.
Attended space missions: STS-114, STS-124, STS-128, STS-135, Atlas V "Curiosity", Delta IV Heavy NROL-15, Atlas V MUOS-2, Delta IV Heavy NROL-37, SpaceX CRS-9, SpaceX JCSAT-16, Atlas V GOES-R.

Offline Star One

  • Senior Member
  • *****
  • Posts: 7512
  • UK
  • Liked: 1204
  • Likes Given: 168
Pluto Orbital Mission
« Reply #3 on: 10/19/2016 05:57 PM »
I wonder how heavy a scientific payload you could get away with using such an orbiter following the proposals Stern is thinking of.
« Last Edit: 10/19/2016 08:12 PM by Star One »

Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 10721
  • Liked: 2250
  • Likes Given: 1
Re: Pluto Orbital Mission
« Reply #4 on: 10/19/2016 07:32 PM »
Back around 2008 or so I was working on a study (the "Launching Science" study that you can find on the internet) and we looked at enabling technologies for a bunch of missions. One of those included solar electric propulsion, and we discussed hooking up an RTG to an electric propulsion system.

Apparently it's not as simple as you might think. For starters, RTGs tend to be heavy, so that goes into the equation for using the EP. But there's also an issue involving power output. Apparently one of the toughest parts of a solar electric propulsion system  is the power controller that turns the electricity from your power source into the ion stream going out the EP. As power increases or decreases it affects that power converter and that's difficult to work out. We asked one of the EP experts if an RTG, which has a very gradual power decline, would be easy to deal with. If I remember correctly, his response was something like "It's not as simple as you'd expect." I don't know why, and I doubt that it is impossible to solve.
« Last Edit: 10/19/2016 07:32 PM by Blackstar »

Offline TakeOff

  • Full Member
  • ***
  • Posts: 332
  • Liked: 72
  • Likes Given: 92
Re: Pluto Orbital Mission
« Reply #5 on: 10/19/2016 07:32 PM »
Pluto's atmosphere at the ground (in the season NH was there) is about 100 times thicker than the upper atmosphere's of terrestrial planets where aerobraking has been performed to date. So there's potential for aerobraking.

Online Phil Stooke

  • Full Member
  • ***
  • Posts: 329
  • Canada
  • Liked: 187
  • Likes Given: 0
Re: Pluto Orbital Mission
« Reply #6 on: 10/19/2016 08:06 PM »
"Sure, just orbit around the Pluto-Charon barycenter like Hydra, Nix, Kerberos, and Styx do."

No, you want to be much closer in.  But good orbit design might reduce or counteract the effects of Charon.  Possibly something like a polar orbit, low periapsis, orbit period 0.5 of Charon.

Offline Wolfram66

Re: Pluto Orbital Mission
« Reply #7 on: 10/19/2016 09:17 PM »
Halo orbit around Pluto Charon center of mass would work... like an L1 or L2 orbit used by Discovr et.al.

Offline bkellysky

  • Member
  • Full Member
  • *
  • Posts: 136
  • Selfie in Surveyor's camera mirror at NASM
  • Ardsley, New York, USA
    • Heads UP!
  • Liked: 21
  • Likes Given: 34
Re: Pluto Orbital Mission
« Reply #8 on: 10/19/2016 10:27 PM »
Aren't Pluto and Charon's rotations tidally locked?
Wouldn't a Charon or L -point outpost always just see the same side of Pluto?

Online whitelancer64

Re: Pluto Orbital Mission
« Reply #9 on: 10/19/2016 10:47 PM »
Aren't Pluto and Charon's rotations tidally locked?
Wouldn't a Charon or L -point outpost always just see the same side of Pluto?
Yes, that's true. We'd miss out on the very intriguing far side of Pluto.

Ideally, I think that a Pluto orbiter would want to get initially captured into a very wide orbit of Pluto, and slowly spiral inwards, so we can get a closer view of everything in the Pluto system from all sides, flybys of the moons, etc. and then later on in the mission get closer in and check out the far side of Charon and Pluto before going for a close-in orbit of Pluto.
"One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to." - Elon Musk
"There are lies, damned lies, and launch schedules." - Larry J

Offline TakeOff

  • Full Member
  • ***
  • Posts: 332
  • Liked: 72
  • Likes Given: 92
Re: Pluto Orbital Mission
« Reply #10 on: 10/28/2016 12:07 PM »
Aren't Pluto and Charon's rotations tidally locked?
Wouldn't a Charon or L -point outpost always just see the same side of Pluto?
Yes, that's true. We'd miss out on the very intriguing far side of Pluto.

Ideally, I think that a Pluto orbiter would want to get initially captured into a very wide orbit of Pluto, and slowly spiral inwards, so we can get a closer view of everything in the Pluto system from all sides, flybys of the moons, etc. and then later on in the mission get closer in and check out the far side of Charon and Pluto before going for a close-in orbit of Pluto.
It seems as if a spacecraft could use aerobraking to enter Pluto's orbit. Its atmospheric density at the surface is about 10^-4 (at the season New Horizon flew by it) and aerobraking to date has been done in atmospheric pressures of about 10^-8. Going at low altitude also maximizes the Oberth effect of braking engines. Aerobraking would be used to lower apohadion (Pluto in Greek, you know) which first most economically is put at the limit of Pluto's Hill sphere, while perihadion remains close to the surface. This in-spiraling would be a natural and economic way to enter orbit. And, as you say, scientifically interesting since it covers all distances in the Pluto system.

Online hop

  • Senior Member
  • *****
  • Posts: 3143
  • Liked: 342
  • Likes Given: 660
Re: Pluto Orbital Mission
« Reply #11 on: 10/28/2016 08:56 PM »
It seems as if a spacecraft could use aerobraking to enter Pluto's orbit.
Unlike, say, a Mars mission, the big dV cost of a Pluto orbiter is slowing down from the arrival, not getting into a specific orbit. To get to Pluto in a reasonable amount of time (like a decade or so...) you need to arrive going > 13 km/s relative to Pluto. The kind of aerobraking you describe wouldn't help. Aerocapture might, but that would be very challenging if it's possible at all.

You might be able to use aerobraking to adjust your orbit within the Pluto system after initial orbit insertion, but that shouldn't be a big deal with conventional methods. Pluto has a puny gravity well (it's ~0.18 Lunar mass), and Charon encounters could probably be used to advantage. You'd certainly want to spend some time close to Charon anyway, either with close encounters or in orbit.

Quote
Its atmospheric density at the surface is about 10^-4 (at the season New Horizon flew by it)
Lack of knowledge of what the atmosphere will be like at arrival would make it a lot harder to design a mission to use it.
« Last Edit: 10/28/2016 08:57 PM by hop »

Offline redliox

  • Full Member
  • ****
  • Posts: 1651
  • Arizona USA
  • Liked: 309
  • Likes Given: 54
Re: Pluto Orbital Mission
« Reply #12 on: 03/06/2017 03:21 AM »
Although no spacecraft specifics mentioned just yet, they have apparently begun discussing what a future Pluto Orbiter would study at the (former?) 9th planet: http://www.lpi.usra.edu/opag/meetings/feb2017/presentations/Buie.pdf

Surface composition and analyzing the interior seem to be implied interest.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline CuddlyRocket

Re: Pluto Orbital Mission
« Reply #13 on: 03/06/2017 06:57 AM »
Surface composition and analyzing the interior seem to be implied interest.

That's unusual! :)

One difficulty in realising this mission is that there's probably lots of other easier orbital missions that people would prefer.


Offline redliox

  • Full Member
  • ****
  • Posts: 1651
  • Arizona USA
  • Liked: 309
  • Likes Given: 54
Re: Pluto Orbital Mission
« Reply #14 on: 03/06/2017 07:34 AM »
Surface composition and analyzing the interior seem to be implied interest.

That's unusual! :)

One difficulty in realising this mission is that there's probably lots of other easier orbital missions that people would prefer.

Pretty much.  However even the scientists discussing the matter acknowledge revisiting Pluto, orbiter or fly-by, is unlikely to happen for decades.  The article I linked specifically mentioned they were discussing the science, not the technology, a Pluto orbiter would hunt.  As far as the technology portion, frankly it just comes down to finding some way to slow a probe down enough to do the job.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Star One

  • Senior Member
  • *****
  • Posts: 7512
  • UK
  • Liked: 1204
  • Likes Given: 168
Pluto Orbital Mission
« Reply #15 on: 04/24/2017 08:01 PM »
An update on this proposed mission from Alan Stern.

Quote
AlanStern‏ @AlanStern

In Houston today, 35 of us-- and we're planning the NEXT mission to Pluto! #Pluto #NASA #Plutoflyby

https://mobile.twitter.com/AlanStern/status/856553179206627328

It is going to be an orbiter.

Quote
Paul Scott Anderson‏ @paulsanderson

Replying to @Dales_Starman and 3 others
In response to a question on Facebook, he says it's an orbiter.

https://mobile.twitter.com/paulsanderson/status/856587099180457984
« Last Edit: 04/24/2017 08:02 PM by Star One »

Offline Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 10721
  • Liked: 2250
  • Likes Given: 1
Re: Pluto Orbital Mission
« Reply #16 on: 04/24/2017 09:00 PM »
So maybe somebody can chime in here and answer if my assumption is correct:

I assume that any orbital mission going to Pluto is going to take longer to reach Pluto than New Horizons did. My reasoning is that New Horizons blasted up to a pretty fast velocity and then zoomed out to Pluto, with no need to slow down. But any orbiter is going to have to slow down, and it is going to have to slow down before it even gets near Pluto, so accelerate, go for a distance, then start slowing down. Instead of a 9-year flight time, it's going to be more, maybe 50% more?

Does that sound reasonable?

I would also guess that they might want some kind of solar electric propulsion system, with RTG-electric for deceleration and orbital insertion.

Offline Bob Shaw

  • Full Member
  • ****
  • Posts: 952
  • Liked: 355
  • Likes Given: 326
Re: Pluto Orbital Mission
« Reply #17 on: 04/24/2017 09:08 PM »
I wonder if some sort of deployable balloon could be used as a parachute to increase the efficiency of aerobraking? Or even a parachute itself? The forces acting on such a device might be qiote extreme if it was being asked to dump a lot of velocity over a brief period.

Offline IanThePineapple

  • Full Member
  • ***
  • Posts: 365
  • NaN
  • Liked: 88
  • Likes Given: 51
Re: Pluto Orbital Mission
« Reply #18 on: 04/24/2017 09:30 PM »
This could be amazing, I could see them doing a Cassini-style mission where you flyby the moons multiple times while also studying the planet
Proud creator of Ian's Paper Model Rocket Collection:
https://forum.nasaspaceflight.com/index.php?topic=42383.0

Online Comga

  • Senior Member
  • *****
  • Posts: 3830
  • Liked: 1196
  • Likes Given: 1019
Re: Pluto Orbital Mission
« Reply #19 on: 04/24/2017 09:55 PM »
So maybe somebody can chime in here and answer if my assumption is correct:

I assume that any orbital mission going to Pluto is going to take longer to reach Pluto than New Horizons did. My reasoning is that New Horizons blasted up to a pretty fast velocity and then zoomed out to Pluto, with no need to slow down. But any orbiter is going to have to slow down, and it is going to have to slow down before it even gets near Pluto, so accelerate, go for a distance, then start slowing down. Instead of a 9-year flight time, it's going to be more, maybe 50% more?

Does that sound reasonable?

I would also guess that they might want some kind of solar electric propulsion system, with RTG-electric for deceleration and orbital insertion.

Not necesssarily.
The brute force approach is to use an enormous rocket (Where would that come from?😉) and production bi-prop engines to break rather quickly into orbit. That results in an orbiter half the mass of New Horizons.
I think it still needs an RTG, which will continue to be hard to come by. But the optimum trajectory might be slower, as you suggest.
As far as I know, without an ASRG (?) we don't have the technology for a continuous thrusting NEP mission, which would take longer to get there as you say. It's been a while since reading those papers.
Dr Stern has my concept for a Pluto orbiter mission. Perhaps he will include it in the trade studies. It's neither of the above, but is similar in aspects to what you suggested.
Any way you cut it, a second mission to Pluto will have to percolate to the top of the priority list, which will take years maybe decades. It will fall again to a new prominent young scientist who will then have the adequate life expectancy to captain what will be a two decade long program.
I hope to live to see it. I ❤️ Pluto (Rationality has its limits)
What kind of wastrels would dump a perfectly good booster in the ocean after just one use?

Tags: