Author Topic: Proposed Europa Missions  (Read 640976 times)

Offline Star One

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Re: Proposed Europa Missions
« Reply #800 on: 03/07/2015 06:32 pm »
Would any kind of electric propulsion such as ion propulsion be of any use for a Europa bound craft?

Offline redliox

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Re: Proposed Europa Missions
« Reply #801 on: 03/07/2015 08:09 pm »
Would any kind of electric propulsion such as ion propulsion be of any use for a Europa bound craft?

Difficult to say.  I'd love to say it'd help but to power a decent propulsion system the craft would need arrays certainly larger than Dawn's by comparison due to the fact Jupiter is farther out and sunlight's strength drops off fast.  Juno proves we're at the cusp of solar power at Jupiter but I'm pretty sure that's nearing the limits of what's practical.

One thing I would say: en route to Jupiter it could be useful, especially if it means bypassing Venus flybys; most likely at least one Earth flyby would be necessary but it would help speed the transit to Jupiter along.  Whether or not it could do Jupiter Orbit Insertion is another matter (again just due to sunlight at that distance).
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Offline Star One

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Re: Proposed Europa Missions
« Reply #802 on: 03/11/2015 04:03 pm »
New article on Europa Clipper's progress. Mentions they'll have to make a choice soon on whether to go with the Juno solar panels or if to go with a more advanced design. Sounds also that they are only really considering Atlas V or SLS for the launcher. It sounds like SLS will be the far better choice if the cost can be resolved as well as fitting it into the SLS schedule.

http://spaceflightnow.com/2015/03/10/europa-clipper-concept-team-aims-for-launch-in-2022/

Offline Blackstar

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Re: Proposed Europa Missions
« Reply #803 on: 03/11/2015 06:47 pm »
New article on Europa Clipper's progress. Mentions they'll have to make a choice soon on whether to go with the Juno solar panels or if to go with a more advanced design. Sounds also that they are only really considering Atlas V or SLS for the launcher. It sounds like SLS will be the far better choice if the cost can be resolved as well as fitting it into the SLS schedule.

http://spaceflightnow.com/2015/03/10/europa-clipper-concept-team-aims-for-launch-in-2022/

That looks to be written based upon somebody listening in to the comments at the OPAG meeting a few weeks ago. Here's the solar cell part:

"“We can either cash that in with less area for the (solar) arrays or more power for the system, to be determined at this point,” Goldstein said. “But we’re not counting on that new technology. We wanted existence proof to show that we had what we needed to make the jump away from (nuclear power).”

Officials hope to decide between the old or new solar cell technology by the middle of 2015, then NASA could begin buying test and flight units as part of the mission’s long-lead purchases, according to Goldstein."


If I remember correctly, they did a bunch of tests using backup Juno solar cells that they had on hand. Their next step was to get some newer solar cells and test them. I would guess that they will be putting those cells in test chambers now or soon and running the tests. I dunno what that entails. In addition to thermal/vac testing, do they also hit them with radiation? I vaguely remember hearing somebody say that cold is a bigger issue than radiation for the cells that they have tested. I don't know exactly what that means. Perhaps it is easier to model the radiation and they have to actually test for the cold. Or maybe it just means that prolonged cold is the bigger killer than radiation.

I know how thermal/vac tests work. But how do they actually test for radiation? Do they zap them in a microwave oven or equivalent? And does this have to be done while also in cold vacuum?

Offline Star One

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Proposed Europa Missions
« Reply #804 on: 03/11/2015 06:51 pm »
I know solar cell technology in general has advanced quite a bit in recent years due to increasing investment in the technology. But I don't know how much general purpose solar cells would relate to the more specialist ones you would need for a mission such as this.
« Last Edit: 03/11/2015 06:52 pm by Star One »

Offline denis

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Re: Proposed Europa Missions
« Reply #805 on: 03/11/2015 07:24 pm »
I know how thermal/vac tests work. But how do they actually test for radiation? Do they zap them in a microwave oven or equivalent? And does this have to be done while also in cold vacuum?

I expect they will submit the cells to a given radiation level and type (so maybe a mixture of gamma rays and high energy protons, to check impact of displacement damages) to reach a total dose equivalent to the mission, then they'll test the cells (in cold vacuum) after irradiation. Most likely (assuming they have enough cells / money), they'll irradiate different cells to different radiation levels (below and above the expected total dose) and compare their performances, to see the degradation over the mission duration.

Contrarily to testing of electronic components, I don't think there is a need to test the cells while they are being irradiated, it can be done in separate steps (so no need to test them while being irradiated and while being in cold vacuum conditions).

Edit: although I admit I don't know if the Jupiter environment is so bad radiation-wise that there is a need for more complex/detailed testing
« Last Edit: 03/11/2015 07:29 pm by denis »

Offline philw1776

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Re: Proposed Europa Missions
« Reply #806 on: 03/11/2015 08:56 pm »
Great thread here on the state of the art on ion thrusters

http://forum.nasaspaceflight.com/index.php?topic=36787.msg0#new

and importantly, the power sources with new solar cell metrics

http://forum.nasaspaceflight.com/index.php?topic=36789.0



FULL SEND!!!!

Offline TheMightyM

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Re: Proposed Europa Missions
« Reply #807 on: 03/14/2015 09:21 pm »
While I have no doubt that the scientist working on Europa Clipper would love to see the mission launch in 2022, getting the funding to do so is may be challenging. Currently, Planetary Science gets about $1.35 billion a year. Europa Clipper is expected to cost near $2 billion (plus launch vehicle). So Congress is going to have to either substantially increase Planetary Science funding and/or some other missions will have to be delayed, with the “and” option being the most likely path towards a 2022 Europa Clipper launch.

What else is NASA planning to do in Planetary Science circa 2020 to 2022?. The Mars 2020 lander is the big budget item, but there’s also talk of a new Mars Orbiter in 2022. NASA is currently working through proposals for a Discovery mission and then wants to select new missions every two to three years. Finally, the next New Frontiers mission is due to be selected in 2017 and gets $100 million by 2020 in the notional out year budget (and probably more like $250 million for 2021 and 2022.) No easy choices there.
« Last Edit: 03/14/2015 09:22 pm by TheMightyM »

Offline redliox

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Re: Proposed Europa Missions
« Reply #808 on: 03/14/2015 09:51 pm »
While I have no doubt that the scientist working on Europa Clipper would love to see the mission launch in 2022, getting the funding to do so is may be challenging. Currently, Planetary Science gets about $1.35 billion a year. Europa Clipper is expected to cost near $2 billion (plus launch vehicle). So Congress is going to have to either substantially increase Planetary Science funding and/or some other missions will have to be delayed, with the “and” option being the most likely path towards a 2022 Europa Clipper launch.

It has a reasonable chance to do so; it does have public support behind it or at least that of planetary scientists.  The real question is which launch vehicle will be ready by 2022.  Still regarding the probe itself, with a decent push it is possible.
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Offline Star One

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Re: Proposed Europa Missions
« Reply #809 on: 03/14/2015 10:38 pm »
While I have no doubt that the scientist working on Europa Clipper would love to see the mission launch in 2022, getting the funding to do so is may be challenging. Currently, Planetary Science gets about $1.35 billion a year. Europa Clipper is expected to cost near $2 billion (plus launch vehicle). So Congress is going to have to either substantially increase Planetary Science funding and/or some other missions will have to be delayed, with the “and” option being the most likely path towards a 2022 Europa Clipper launch.

It has a reasonable chance to do so; it does have public support behind it or at least that of planetary scientists.  The real question is which launch vehicle will be ready by 2022.  Still regarding the probe itself, with a decent push it is possible.
The Mars orbiter proposal isn't all that definite at the moment to be worrying about its cost.
« Last Edit: 03/14/2015 10:42 pm by Star One »

Online Bob Shaw

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Re: Proposed Europa Missions
« Reply #810 on: 03/15/2015 12:53 am »
Sounds like poor old Venus is off the register, despite it being the only other genuinely Earth-class planet in our Solar System. If we're looking at the evolution of such planetary objects at all, then it demands much more attention. The USSR dominated past Venus research almost by accident after their early probes did well and drew political support, and since then the dearth of large-scale efforts (notwithstanding NASA's 1970/80s Pioneer and Magellan missions, and ESA's more recent repurposed Mars orbiter) has been pretty obvious. Venus is the Titan of the Inner Solar system, with lessons for all sorts of disciplines, and demands much more attention.

Here's the facts. Earth's land mass is about 30% of the planet; Venus, though smaller, has a surface area 95% of the total of the Earth including the oceans. Unlike the Earth, all of Venus is visible from orbit in exactly the same way (mostly RADAR) - the only Earth-sized planet which may make that claim. The surface of Mars is about equal to the surface area of Earth, and the Moon is about the same size as Africa - and both of these worlds are easily seen optically from orbit, and are reasonably easy to land on.

Venus isn't the low-hanging fruit in terms of planetary science, but certainly is a key aspect of the whole business of the evolution of Earth-class planets, and has been seriously undervalued.


« Last Edit: 03/15/2015 12:55 am by Bob Shaw »

Offline JH

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Re: Proposed Europa Missions
« Reply #811 on: 03/15/2015 02:21 am »
I'm pretty sure Dr. Elachi (JPL director) has said that NASA will be talking to ISRO about including an Electra comm package onboard MOM II. Also, there is a lot of pent up interest in a new Venus mission, so it wouldn't be terribly surprising if a proposal is funded before too long. I know that some of the different proposal teams from the last go round have clubbed together this time, which should help their chances.

Online vjkane

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Re: Proposed Europa Missions
« Reply #812 on: 03/15/2015 05:05 am »
2-Agreed. I would think that simply from a programmatic perspective NASA officials, if presented with a viable Venus mission, would recognize that it has been a long time since the last NASA Venus mission and therefore Venus is due. But they have to get a viable mission that they can support.
I am thinking that NASA has received viable proposals.  Venus missions have been finalists for two New Frontiers competitions and at least one Discovery competition.  A number of groups have proposed radar mapping missions (which would address Bob Shaw's points) and various descent probes and balloon missions. 

Have you heard that there were technical or budget issues with the numerous Discovery Venus proposals?

Offline Star One

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Proposed Europa Missions
« Reply #813 on: 03/15/2015 08:51 am »
Sounds like poor old Venus is off the register, despite it being the only other genuinely Earth-class planet in our Solar System. If we're looking at the evolution of such planetary objects at all, then it demands much more attention. The USSR dominated past Venus research almost by accident after their early probes did well and drew political support, and since then the dearth of large-scale efforts (notwithstanding NASA's 1970/80s Pioneer and Magellan missions, and ESA's more recent repurposed Mars orbiter) has been pretty obvious. Venus is the Titan of the Inner Solar system, with lessons for all sorts of disciplines, and demands much more attention.

Here's the facts. Earth's land mass is about 30% of the planet; Venus, though smaller, has a surface area 95% of the total of the Earth including the oceans. Unlike the Earth, all of Venus is visible from orbit in exactly the same way (mostly RADAR) - the only Earth-sized planet which may make that claim. The surface of Mars is about equal to the surface area of Earth, and the Moon is about the same size as Africa - and both of these worlds are easily seen optically from orbit, and are reasonably easy to land on.

Venus isn't the low-hanging fruit in terms of planetary science, but certainly is a key aspect of the whole business of the evolution of Earth-class planets, and has been seriously undervalued.

I would argue that Venus has had its fair share of recent missions whereas many of the objects in the outer solar system haven't been studied in that detail. With news only this week about the oceans beneath the surface of two further moons I would rather things like this be looked into especially when you have moons such as Io, Titan, Enceladus or planets such as Uranus & Neptune that need proper examination. To be blunt if you want missions that are going to get public support and therefore political interest to follow you're more likely to get that with the dangling hook of possible life no matter how remote a possibility that is than with a planet like Venus which has no chance of this. After all I suspect that's half the reason Mars has had many more missions than Venus.

I know it's not a very scientific answer, but missions have to get political & financial support if they are going to transit to reality and that's not always a logical process.
« Last Edit: 03/15/2015 09:23 am by Star One »

Online vjkane

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Re: Proposed Europa Missions
« Reply #814 on: 03/15/2015 02:01 pm »
Have you heard that there were technical or budget issues with the numerous Discovery Venus proposals?

Last Discovery round none made it to category 1.
That's not the same as saying that there were no credible Venus proposals. 

One way to interpret the finalists is that there was one per class of destination: terrestrial planets (InSight), small bodies (CHOPPER), outer planets (TiME).

There are several possible explanations for why no Venus missions made it to the finalist list.

It could be a prejudice towards Mars. 

It could be that the Venus missions proposed were technically and financially credible but that the science questions weren't compelling to the team that ranked the missions (which could either be seven poor proposals or a prejudice against Venus (too boring) on the part of the review teams)

It could be that the science questions were compelling but they couldn't be done within the cost cap of the Discovery program.

When there's no public data, it's hard to make any conclusions.  I suspect that the Venus community privately shared the top level results of their proposal reviews.  VEXAG has put a lot of emphasis in the last couple of years on sharpening the science priorities for Discovery class missions, so perhaps the problem was a lack of compelling science questions.

Offline redliox

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Re: Proposed Europa Missions
« Reply #815 on: 03/15/2015 06:29 pm »
The whole Venus/Discovery/New Frontiers discussion is good but...why are we bringing this up HERE when there are distinct Discovery and New Frontiers threads?
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Offline Star One

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Re: Proposed Europa Missions
« Reply #816 on: 03/16/2015 11:55 am »

I would argue that Venus has had its fair share of recent missions

Name the recent missions to Venus. With dates.

Venus Express only just finished. Akatsuki still active & due in orbit this year.

Offline Blackstar

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Re: Proposed Europa Missions
« Reply #817 on: 03/16/2015 03:36 pm »

I would argue that Venus has had its fair share of recent missions

Name the recent missions to Venus. With dates.

Venus Express only just finished. Akatsuki still active & due in orbit this year.

So, "fair share" means one mission, launched in 2005, now dead, and one mission that hasn't actually reached Venus and may not work because the spacecraft is severely damaged. And before that, Magellan, launched in 1989.

So, two missions in 25 years.

Online vjkane

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Re: Proposed Europa Missions
« Reply #818 on: 03/16/2015 03:46 pm »
So, two missions in 25 years.
And both are focused on the atmosphere and not the surface or interior

Offline Star One

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Re: Proposed Europa Missions
« Reply #819 on: 03/16/2015 04:14 pm »

I would argue that Venus has had its fair share of recent missions

Name the recent missions to Venus. With dates.

Venus Express only just finished. Akatsuki still active & due in orbit this year.

So, "fair share" means one mission, launched in 2005, now dead, and one mission that hasn't actually reached Venus and may not work because the spacecraft is severely damaged. And before that, Magellan, launched in 1989.

So, two missions in 25 years.
If we are going to play this game how many dedicated missions has there ever been to any of the targets I mentioned, none in most cases, which is a heck of a lot less than Venus and that was my point.
« Last Edit: 03/16/2015 04:15 pm by Star One »

 

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