Author Topic: Missions to the Ice Giants Uranus and Neptune  (Read 342267 times)

Offline baldusi

  • Senior Member
  • *****
  • Posts: 8356
  • Buenos Aires, Argentina
  • Liked: 2539
  • Likes Given: 8273
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #580 on: 06/15/2017 08:35 pm »
BTW, aerocapture on Earth is proven. The problem is arrocapture in a world where you don't understand the atmosphere. In addition, the maneuver, AIUI, depends on the local conditions, not something forecasted, but observed. In Earth it's trivial, but you can't get an Eumesat report of weather at Uranus.


Sent from my iPhone using Tapatalk

Offline gosnold

  • Full Member
  • ****
  • Posts: 572
  • Liked: 243
  • Likes Given: 2116
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #581 on: 06/15/2017 08:38 pm »
Aerocapture and optical-coms are acknowledged as being potentially useful but not likely to happen.

They are not that pessimistic:
Quote
In summary the prospect of implementing laser links from Icy Giants will result in a significant
boost to returned information capacity from the outer solar system. The links presented in this report are conservative and based on reasonable extrapolation of existing technologies. The most
formidable challenge is the formulation of an affordable architecture to support pointing back of
the laser beam from the outer reaches of the solar system
. If this problem is solved the data-rates
reported here can be further improved by scaling the laser power either through technology
development or wavelength multiplexing of existing laser technology.

Online Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 15288
  • Liked: 7823
  • Likes Given: 2
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #582 on: 06/15/2017 10:48 pm »
BTW, aerocapture on Earth is proven. The problem is arrocapture in a world where you don't understand the atmosphere. In addition, the maneuver, AIUI, depends on the local conditions, not something forecasted, but observed. In Earth it's trivial, but you can't get an Eumesat report of weather at Uranus.

My understanding of the issue is that it isn't really about materials (i.e. what kind of ablative stuff to put on the spacecraft), but more about sensing and responding. So the vehicle goes in and has to actively sense what it's moving through and then fly to respond to it. That's harder to do when you have very limited data about the composition of the atmosphere. As a for instance, suppose the spacecraft enters and the sensors detect that the atmosphere is thinner than expected, so the computer steers the vehicle in deeper in order to slow down, but then it suddenly encounters much denser atmosphere, and now it's too deep to steer up and get to less dense atmosphere before it burns up. So somehow better data is required to do this.

And my guess is that the issue isn't a simple yes/no impossible/possible, but like many engineering problems it involves margins. So you could design a spacecraft with lots of margin to deal with a wide range of unknowns, but then it becomes heavy, so what you want to do is reduce the unknowns so that you can reduce the margins applied to the vehicle.

(A couple of years ago I had a really interesting discussion with somebody who had worked on reentry models for DreamChaser and he explained how all reentry vehicles in use today had much larger margins than they needed. The reason had to do with the data that fed into the engineering models that are used to design heat shields--the data collection has actually been poor, so the engineering models have larger margins, and this has then propagated into the vehicles. And, as he noted, we've been doing lots of reentry for decades, but there were very few efforts to collect direct sensor data from the heat shields themselves. It was a case where you would think that the technology is mature and the modeling is mature and sophisticated, but that's not actually the case.)

Online LouScheffer

  • Senior Member
  • *****
  • Posts: 3382
  • Liked: 6109
  • Likes Given: 837
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #583 on: 06/15/2017 11:10 pm »
[...] suppose the spacecraft enters and the sensors detect that the atmosphere is thinner than expected, so the computer steers the vehicle in deeper in order to slow down, but then it suddenly encounters much denser atmosphere, and now it's too deep to steer up and get to less dense atmosphere before it burns up.

This problem should be easier at giant planets - their atmosphere is thick, so changes are more gradual.   This is measured by scale height, the altitude change you need to change the density by a factor of 'e'.  For the Earth this is 8.5 km, but for Uranus about 27 km and Neptune about 20 km.  So the job of the spacecraft, maintaining itself at an altitude with the correct deceleration, should be 2-3 times easier (compared to Earth) at Neptune or Uranus.

Offline vjkane

  • Full Member
  • ****
  • Posts: 1269
  • Liked: 617
  • Likes Given: 5
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #584 on: 06/16/2017 02:12 am »
Working this out (the dual mission) would be somewhat difficult. The reason is that you get some economy from building near-identical spacecraft, and it's not going to be possible to do that and have NASA build one and ESA build the other. So the logical thing to do would be to have NASA (JPL or APL) build two spacecraft and have the international partners contribute dual copies of many instruments. That of course gets thornier because the United States has scientists who want to supply instruments. JAXA could also supply instruments too.

These agreements require "clean interfaces" and bartering goods and services, not money, which means that NASA cannot just build the spacecraft and expect ESA to send over money.

Like I said, not easy. But not impossible.
One preferred solution in the report was a Uranus orbiter with a Neptune flyby and probe.  Such a mission could be launched by SLS, but not other launch vehicles.   To fit within a reasonable mass, only one spacecraft could carry the fuel for orbit; Uranus has the advantage over Neptune of not requiring a SEP stage.

The concept in the report was for nearly identical spacecraft, which would have several eMMRTGs, providing power to operate numerous instruments and to send a reasonably large volume of data back to Earth.

However, another option might be for another space agency to build a smaller carrier craft (I'm thinking New Horizon's class) for the Neptune flyby.  It could carry two of the minimum instruments, the narrow angle camera and the magnetometer.  It's not clear whether the craft, which might have just one eMMRTG, could send enough data back to enable a reasonable Doppler imaging experiment.  We know that a New Horizon-class spacecraft can also carry a visible-near IR spectrometer and an ultraviolet spectrometer.  A smaller spacecraft could enable the use of a less expensive launch vehicle if the SLS is not available.  Presumably, NASA would provide the eMMRTG, and under the requirements of current US law, the launch vehicle.

For those of you who are more launcher savvy than I, could an Ariane 6 send an orbiter and possibly a probe, to Uranus?

Other split of responsibilities might be for another agency to build the descent probe.  The report listed NASA's HEET entry thermal technology as an enabling technology.  I don't know whether another agency is working on equivalent technology.  So NASA might build the heat shield.

Offline vjkane

  • Full Member
  • ****
  • Posts: 1269
  • Liked: 617
  • Likes Given: 5
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #585 on: 06/16/2017 02:17 am »
The report recommends the use of 4 to 5 eMMRTGs for an orbiter mission.  If a second craft were built as either an orbiter or a flyby, it would require an additional 4 to 5 eMMRTGs.

Anyone know if NASA is expected to have that much plutonium available by the late 2020s, when the eMMRTGs are likely be fueled?

Online Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 15288
  • Liked: 7823
  • Likes Given: 2
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #586 on: 06/16/2017 02:26 am »
This problem should be easier at giant planets -

The people who have looked at this subject say otherwise.

Online Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 15288
  • Liked: 7823
  • Likes Given: 2
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #587 on: 06/16/2017 02:28 am »
The report recommends the use of 4 to 5 eMMRTGs for an orbiter mission.  If a second craft were built as either an orbiter or a flyby, it would require an additional 4 to 5 eMMRTGs.

Anyone know if NASA is expected to have that much plutonium available by the late 2020s, when the eMMRTGs are likely be fueled?

One of the things we're hoping to get with the planetary midterm is an indication of Pu-238 stockpiles.


Offline Star One

  • Senior Member
  • *****
  • Posts: 13997
  • UK
  • Liked: 3974
  • Likes Given: 220
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #588 on: 06/16/2017 06:51 pm »
It’s time to explore Uranus and Neptune again — and here's how NASA could do it

Additional quotes from one of the author's to The Verge.

Quote
“The curious thing about Uranus and Neptune is that, although they look very similar, something about their interiors is actually quite a bit different,” Jonathan Fortney, a professor at UC Santa Cruz and one of the authors on the report, tells The Verge. “And we don’t really know why that is.”

Quote
The focus on Uranus is mostly a matter of distance, says Fortney. “Neptune’s further away and it takes longer to get there, so missions to Neptune are always going to be more expensive,” he says. All four mission plans would run about $2 billion each — a little more than half the cost of the Cassini mission at Saturn.

Quote
Though four missions are proposed, realistically only one could be picked. “There’s no way there’d be money for more than one,” says Fortney.

Quote
Sill Fortney says now is the time to think about getting started on one of these missions. The year 2029 may seem far off, but spacecraft take years to develop. “You can’t just wait around till the mid 2020s,” he says. “Too much time would have passed.” But soon the planetary science community will meet again to determine the top mission priorities for the years ahead. This most recent report will factor into those decisions, and Fortney thinks there may be a strong case to go to Uranus and Neptune.

“I think those are going to be some of the main science targets of the next decade,” he says.

https://www.theverge.com/2017/6/16/15810926/nasa-uranus-neptune-mission-voyager-2-spacecraft

Online redliox

  • Senior Member
  • *****
  • Posts: 2539
  • Illinois USA
  • Liked: 683
  • Likes Given: 97
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #589 on: 09/16/2017 04:43 am »
A nicely fleshed out report made in June but released earlier this month: http://www.lpi.usra.edu/icegiants/mission_study/Full-Report.pdf
Includes details down to instrument selection and trajectory; for example the Neptune orbiter with probe would do a single fly-by of Earth and Jupiter en route to Neptune while utilizing SEP.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Star One

  • Senior Member
  • *****
  • Posts: 13997
  • UK
  • Liked: 3974
  • Likes Given: 220
Missions to the Ice Giants Uranus and Neptune
« Reply #590 on: 09/27/2017 07:26 pm »
Apparently the Chinese have plans for a mission to Uranus around 2048.

https://mobile.twitter.com/AJ_FI/status/912948443601096705

Also Ganymede has interested them as well.

https://mobile.twitter.com/AJ_FI/status/912977413457551360
« Last Edit: 09/27/2017 07:28 pm by Star One »

Offline vjkane

  • Full Member
  • ****
  • Posts: 1269
  • Liked: 617
  • Likes Given: 5
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #591 on: 09/27/2017 07:43 pm »
Apparently the Chinese have plans for a mission to Uranus around 2048.

https://mobile.twitter.com/AJ_FI/status/912948443601096705

Also Ganymede has interested them as well.

https://mobile.twitter.com/AJ_FI/status/912977413457551360
The slide also shows a Chinese Mars sample return in the 2020s.  I wonder if this is lighting a fire under NASA?

Offline whitelancer64

Re: Missions to the Ice Giants Uranus and Neptune
« Reply #592 on: 09/27/2017 08:12 pm »
Apparently the Chinese have plans for a mission to Uranus around 2048.

https://mobile.twitter.com/AJ_FI/status/912948443601096705

Also Ganymede has interested them as well.

https://mobile.twitter.com/AJ_FI/status/912977413457551360
The slide also shows a Chinese Mars sample return in the 2020s.  I wonder if this is lighting a fire under NASA?

NASA would love to do those things whether China was doing them or not. It's congress you want to look for some flames.
"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 vjkane

  • Full Member
  • ****
  • Posts: 1269
  • Liked: 617
  • Likes Given: 5
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #593 on: 09/27/2017 08:41 pm »
The slide also shows a Chinese Mars sample return in the 2020s.  I wonder if this is lighting a fire under NASA?

NASA would love to do those things whether China was doing them or not. It's congress you want to look for some flames.
This summer NASA's managers have shown a renewed strong interesting in doing sample return in the 2020s instead of in the vague, usually 2030s, they had before.

Offline whitelancer64

Re: Missions to the Ice Giants Uranus and Neptune
« Reply #594 on: 09/27/2017 08:46 pm »
The slide also shows a Chinese Mars sample return in the 2020s.  I wonder if this is lighting a fire under NASA?

NASA would love to do those things whether China was doing them or not. It's congress you want to look for some flames.
This summer NASA's managers have shown a renewed strong interesting in doing sample return in the 2020s instead of in the vague, usually 2030s, they had before.

That's when the plans for the 2020 rover had firmed up.
"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

Online redliox

  • Senior Member
  • *****
  • Posts: 2539
  • Illinois USA
  • Liked: 683
  • Likes Given: 97
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #595 on: 02/12/2018 07:23 pm »
An updated list of goals for the The Outer Planets Assessment Group (OPAG):https://www.lpi.usra.edu/opag/goals-02-12-18.pdf

In addition to this, the OPAG will have their official meeting in just over a week.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Star One

  • Senior Member
  • *****
  • Posts: 13997
  • UK
  • Liked: 3974
  • Likes Given: 220
Missions to the Ice Giants Uranus and Neptune
« Reply #596 on: 04/01/2018 08:43 pm »
This concept is relevant up this thread.

Triton Hopper: Exploring Neptune's Captured Kuiper Belt Object

Phase II for the Triton Hopper will focus on retiring the risks identified in Phase I and providing better detail and alternate conceptual options. The three main risks to be addressed include Triton hopper mission, propellant collection, and propulsion performance. For the Triton mission both delivery to Triton in a timely manner ~ 15 yrs and safe takeoff and landing of the hopper on the Triton terrain will be explored. For propellant collection a bevameter experiment will be performed on a small sample of frozen nitrogen to assess ways to best gather the frozen nitrogen propellant. For the propulsion performance ways will be explored to heat the propellant to higher temperatures and or to reduce dry mass to enable further hops. Using these three products two Compass concurrent engineering runs will be performed; the first of which focusses on integrating the findings of mission/propellant collection and the second on integrating the findings which increase hop distance. Phase II will end with roadmapping technology development solutions as well as using such techniques for other icy worlds to gather propellants for hopping.

https://www.nasa.gov/directorates/spacetech/niac/2018_Phase_I_Phase_II/Triton_Hopper
« Last Edit: 04/01/2018 08:44 pm by Star One »

Online redliox

  • Senior Member
  • *****
  • Posts: 2539
  • Illinois USA
  • Liked: 683
  • Likes Given: 97
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #597 on: 04/03/2018 01:21 am »
This concept is relevant up this thread.

Triton Hopper: Exploring Neptune's Captured Kuiper Belt Object

Good to see this idea is still being...bounced...around  ;)

Still an excellent idea, although I wouldn't expect it to be prioritized over the orbiter and probe options; some time ago the study groups culled the prospects of cubesats and landers.
"Let the trails lead where they may, I will follow."
-Tigatron

Online Blackstar

  • Veteran
  • Senior Member
  • *****
  • Posts: 15288
  • Liked: 7823
  • Likes Given: 2
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #598 on: 04/03/2018 01:33 am »
This concept is relevant up this thread.

Triton Hopper: Exploring Neptune's Captured Kuiper Belt Object

Good to see this idea is still being...bounced...around  ;)

Still an excellent idea, although I wouldn't expect it to be prioritized over the orbiter and probe options; some time ago the study groups culled the prospects of cubesats and landers.

This is a NIAC study, which means it is very very early concept. It needs a lot of work before anybody will consider it for a flight mission. A friend of mine runs the NIAC program. He told me at LPSC that they were about to announce the new awards and said that he was impressed with the quality of the proposals they were getting.

Offline Star One

  • Senior Member
  • *****
  • Posts: 13997
  • UK
  • Liked: 3974
  • Likes Given: 220
Re: Missions to the Ice Giants Uranus and Neptune
« Reply #599 on: 05/03/2018 08:00 pm »

Tags:
 

Advertisement NovaTech
Advertisement Northrop Grumman
Advertisement
Advertisement Margaritaville Beach Resort South Padre Island
Advertisement Brady Kenniston
Advertisement NextSpaceflight
Advertisement Nathan Barker Photography
1