Author Topic: Proposed Europa Missions  (Read 316176 times)

Offline Moe Grills

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Re: Proposed Europa Missions
« Reply #780 on: 02/21/2015 04:57 PM »
Personally, I don't mind gravity-assists if it means a planned mission comes in under budget.
I have a good hunch that politicians are weary and wary of planetary mission projects that
have serious cost overruns.

BTW, I wish JUICE would end up orbiting Europa instead of doing multiple flybys. Technically it's possible; it wouldn't be harder IMHO than sending a spacecraft to orbit Mercury.

Offline vjkane

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Re: Proposed Europa Missions
« Reply #781 on: 02/21/2015 05:46 PM »
Where did you hear 28 Discovery proposals? On Thursday Green said that he did not know how many they received. I heard Alfred McEwen say 28, but 28 was the number last year and I assumed that he made a mistake when he said that was the number for this year.
As Green was preparing to talk about the <$1B Europa proposals, he said that there had been an error in his slides the previous day that said the Discovery down selection would be in May when it should have said September.  He then said that they received 28 proposals and it would take them some time to get through them.

Offline Zed_Noir

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Re: Proposed Europa Missions
« Reply #782 on: 02/21/2015 09:07 PM »
http://spacenews.com/europa-clipper-team-seeking-earlier-launch/?_wcsid=FBF7A9E96BE3C2239D3BAF4A4638A03433FDA26192541BE07BCB7699D6C55D9A

Europa Clipper Team Seeking Earlier Launch

So I am guessing that the SLS launcher option is iffy for a 2022 launch. What are the alternate launcher options?

I suppose Falcon Heavy might still be too new a launcher to be entrusted with such an important mission, as I get the feeling that the dispensation that SLS gets on this wouldn't be applicable to another newish launcher. Especially as from what I have read on here they need to develop a high energy upper stage for it to be used on missions such as this.
By 2022, even only flying a few times per year, falcon heavy will have ~20 flights under its belt. If they add a centaur/rl-10 based upper, the risk is in the integration and ground ops, not the upper stage itself. SLS has its own risk structure as well, and there are some planetary folks still sore about being politically married to a launcher.
You can't add that. The four options are:
1) Atlas V 551 (gotta watch for replacement by NGLV)
2) SLS
3) Delta IV Heavy with kick stage (something like OrbitalATK's Star 48GXV)
4) Falcon Heavy (non cross feed) with something like OrbitalATK's Star 48GXV or whatever Aerojet comes up with.

You think the Atlas V & Delta IV will still be flying in 2022?

My option list will be
1) Falcon Heavy with kick stage in the total expandable configuration with cross feed
2) NGLV (aka Blue Atlas) with supplemental SRMs and kick stage
3) SLS

Presuming the NGLV enters service around 2020. Historical precedence that NASA launched the New Horizon mission on the third Atlas V 500 series flight with a new unique stack configuration.

Offline vjkane

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Re: Proposed Europa Missions
« Reply #783 on: 02/21/2015 09:14 PM »
BTW, I wish JUICE would end up orbiting Europa instead of doing multiple flybys. Technically it's possible; it wouldn't be harder IMHO than sending a spacecraft to orbit Mercury.
Designing JUICE to take the radiation of Europan orbit would probably add $2-3B to the current ~$1B budget.  That's why it makes two quick flybys and then stays away from the intense radiation belts.

Offline baldusi

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Re: Proposed Europa Missions
« Reply #784 on: 02/21/2015 10:34 PM »
[...]
The four options are:
1) Atlas V 551 (gotta watch for replacement by NGLV)
2) SLS
3) Delta IV Heavy with kick stage (something like OrbitalATK's Star 48GXV)
4) Falcon Heavy (non cross feed) with something like OrbitalATK's Star 48GXV or whatever Aerojet comes up with.
SLS aside would all the others need gravity assists?
From what I understand, AV 551 would need a one pass through Earth and two through Venus.
We know that SpaceX is not going to develop the cross feed, at least for now, so what sort of performance to expect with a kick stage, is anyone's guess. Europa Clipper is not an under-300kg like New Horizons but a full 6,000kg or so Flagship Mission. A kick stage might be as big as a small LV upper stage. And it should be pretty reliable, so it has to have heritage or a very simple and thoroughly tested project like the Star 48GXV. And please, don't get me started on putting a Centaur on top of a FH or DIVH.
A similar situation happens with the Delta IV Heavy. It has something like a 45% extra performance to GTO. If high energy is about that, too, then you might save some GA maneuvers.
The fact is that something bigger than an AV 511, might save the Venus passes, which are big culprits in cost for the Atlas V case. It might take the same time, but saving the hotter Venus orbit passes save a lot of cost.
The ULA's NGLV is anyone's guess. It will take some time to transition, probably close to five years, since NRO won't want to commit to it until at least the first launch. And it does takes about five years for integration. Given the expected debut in 2019 for NGLV, it's quite probably that even the last Delta IV Heavy will fly by 2023 or even 2025. Which is about the expected launch date of this mission. If it were to launch on 2025 onwards, the NGLV might even get the improved upper stage by then. And if it covers the full range of performance to Delta IV Heavy, it will obviously be a contender.

Offline redliox

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Re: Proposed Europa Missions
« Reply #785 on: 02/24/2015 10:22 PM »
The OPAG released this update from their February meeting: http://www.lpi.usra.edu/opag/feb2015/presentations/04_Clipper%20OPAG%20Feb%202015.pdf

They clearly put a lot of thought into the solar arrays, and concluded it's worth the effort.  I find it ironic that they might actually outlive the MMRTG power supply.  I'm honestly surprised they proved lighter and more efficient to use than MMRTGs, but apparently the equipment and shielding for plutonium is heftier than even a large pair of wings.  Otherwise the remaining concern is ensuring they don't affect the pointing for optical and infrared imaging.

Otherwise personally I find solar arrays more aesthetically pleasing...although that's not how engineers should think.  ;)

It also looks like there will be more meetings toward the fall of this year and then a review in July of '16.
"Let the trails lead where they may, I will follow."
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Offline Blackstar

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Re: Proposed Europa Missions
« Reply #786 on: 02/25/2015 01:00 AM »
They clearly put a lot of thought into the solar arrays, and concluded it's worth the effort.  I find it ironic that they might actually outlive the MMRTG power supply.  I'm honestly surprised they proved lighter and more efficient to use than MMRTGs, but apparently the equipment and shielding for plutonium is heftier than even a large pair of wings.  Otherwise the remaining concern is ensuring they don't affect the pointing for optical and infrared imaging.

I believe that one of the issues is that the MMRTGs have a faster power drop off rate than the older RTGs. Not quite sure why, but I can find out. The MMRTG was made to be more robust to survive landing on Mars. My guess would be that this includes more structure that cuts down on the heat transfer and thus the power drops off faster.

During the presentation they said that so far they have been testing spare solar cells from Juno. Those are not the most efficient arrays and the next phase of testing they want to do would be testing higher power arrays to see if they work as well.

Offline redliox

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Re: Proposed Europa Missions
« Reply #787 on: 02/25/2015 01:15 AM »
They clearly put a lot of thought into the solar arrays, and concluded it's worth the effort.  I find it ironic that they might actually outlive the MMRTG power supply.  I'm honestly surprised they proved lighter and more efficient to use than MMRTGs, but apparently the equipment and shielding for plutonium is heftier than even a large pair of wings.  Otherwise the remaining concern is ensuring they don't affect the pointing for optical and infrared imaging.

I believe that one of the issues is that the MMRTGs have a faster power drop off rate than the older RTGs. Not quite sure why, but I can find out. The MMRTG was made to be more robust to survive landing on Mars. My guess would be that this includes more structure that cuts down on the heat transfer and thus the power drops off faster.

Given how radioactive material decays, perhaps it has to do with them using less material; they may be able to generate the same amount of power or even better but a smaller stockpile inevitably falls apart faster.

During the presentation they said that so far they have been testing spare solar cells from Juno. Those are not the most efficient arrays and the next phase of testing they want to do would be testing higher power arrays to see if they work as well.

Makes sense to me.  I wager they'll want to minimize R&D so there's bound to be a lot of heritage from Juno, and looking at the IVO presentations it is even more obvious there.
"Let the trails lead where they may, I will follow."
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Offline baldusi

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Re: Proposed Europa Missions
« Reply #788 on: 02/25/2015 01:49 PM »
For me, the most interesting finding is that:
Quote
MCR Findings (4 of 7)
A Class A risk classification for the mission may be overly constraining the system designs and trades, and not truly being applied consistently across the board, a Class B classification is recommended
Even a 2.1B Flagship mission is classified as a Class B payload. It might still require a Category 3 certified LV, but still less than A level mission assurance requirements. In my book that means that they are willing to take reasonable risks.
Other interesting items:
-Atlas V has a 43% mass margin vs SLS's 38% (req. is 30%). But id does require more complexity for Venus GA environment.
-It would seem that DIVH can save a few years, but requires a customized S/C and thus they won't use the extra capability.
-SLS means the simplest and fastest mission, and is the prefered method, but this is just a transfer of risk from S/C to LV certification.
-There's simply no mention of the Falcon Heavy.
-The limiting volume envelop is the Atlas V.

Offline Roly

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Re: Proposed Europa Missions
« Reply #789 on: 02/25/2015 02:38 PM »
I found the Delta IV option very interesting; insofar as possibility of no VEEGA (I had always assumed all of the EELVs required it for any substantial S/C to Jupiter), but appreciate the programmatic complexity/risk. 

Is there any appropriately certified, or even slightly bespoke Atlas V (e.g not a remix of Titan-Centaur), that can possibly avoid the need for VEEGA?  I am assuming not, but it certainly would be interesting, given that there must be some level of unease about SLS, and issues with keeping LV options too open or too closed.   I suppose even if there was, it would not be with any kind of remotely acceptable margin. 

Apologies, this is probably very obvious; I sort of worry about VEEGA, for the SC, and for the nerves humans presiding over the SC for such prolonged cruise, after so many false starts for Europa, and after Galileo (not that it was the VEEGA, but more perhaps a residual nervousness about a major Jovian satellites mission).  And, of course, I am desperate to see its arrival, in a selfish sense.

Cheers,
Roly

Offline Blackstar

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Re: Proposed Europa Missions
« Reply #790 on: 03/02/2015 08:41 PM »
New article on Europa plumes in Science.

Offline Blackstar

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Re: Proposed Europa Missions
« Reply #791 on: 03/03/2015 04:46 PM »
Presentation to OPAG.

Offline Jim

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Re: Proposed Europa Missions
« Reply #792 on: 03/04/2015 01:11 AM »

Is there any appropriately certified, or even slightly bespoke Atlas V (e.g not a remix of Titan-Centaur),


Bespoke?

Offline Roly

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Re: Proposed Europa Missions
« Reply #793 on: 03/04/2015 02:35 AM »
Apologies, in the sense of tailored; but probably the fact that I could not compose it without bespoke or tailored is telling that any such LV is not really a plausible idea...

Offline Jim

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Re: Proposed Europa Missions
« Reply #794 on: 03/04/2015 08:18 AM »
Apologies, in the sense of tailored; but probably the fact that I could not compose it without bespoke or tailored is telling that any such LV is not really a plausible idea...

Ok, but why the reference to Titan-Centaur, which is a completely different and no longer existing vehicle?

Offline redliox

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Re: Proposed Europa Missions
« Reply #795 on: 03/04/2015 08:34 AM »
Well odds are it now looks like the Delta 4 won't be the launcher option for 'Clipper:
http://spacenews.com/ula-targets-2018-for-delta-4-phase-out-seeks-relaxation-of-rd-180-ban/
This makes me wonder if the Atlas V will also be affected by ULA's desire to phase into a NGLV as well as replacing the Russian engines.  If so, this leaves Falcon (Heavy I presume) and SLS as the choice launchers.
"Let the trails lead where they may, I will follow."
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Offline Roly

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Re: Proposed Europa Missions
« Reply #796 on: 03/04/2015 09:52 AM »
It was not well expressed; the reference to my hypothetical 'adjusted' or modified, but not radically changed EELV (which is a bit contradictory) mentioned 'not Titan-Centaur' as a boundary for the sort of changes I meant. 

That is to say, not fantastical ones, like the absurd case of an imaginary, resurrected Titan-Centaur, but moderate ones.  It was meant to gesture to something slightly enhanced or reconfigured, but not crazily impractical and futile.  Re-reading my post, Titan-Centaur was ill-chosen because it is sufficiently ludicrous that it does not provide much of an outer bound to speculation. 

Offline Jim

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Re: Proposed Europa Missions
« Reply #797 on: 03/04/2015 12:15 PM »

This makes me wonder if the Atlas V will also be affected by ULA's desire to phase into a NGLV as well as replacing the Russian engines.  If so, this leaves Falcon (Heavy I presume) and SLS as the choice launchers.

It isn't affected, Atlas V is a choice.  Anyways, the ban was for military missions.

Offline redliox

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Re: Proposed Europa Missions
« Reply #798 on: 03/06/2015 07:02 PM »

This makes me wonder if the Atlas V will also be affected by ULA's desire to phase into a NGLV as well as replacing the Russian engines.  If so, this leaves Falcon (Heavy I presume) and SLS as the choice launchers.

It isn't affected, Atlas V is a choice.  Anyways, the ban was for military missions.

Naturally it's a choice.  The question is will it still be a choice ten years from now; exception being if 'Clipper succeeds in launching by '22.
"Let the trails lead where they may, I will follow."
-Tigatron

Offline Blackstar

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Re: Proposed Europa Missions
« Reply #799 on: 03/07/2015 06:09 PM »
Free event April 9 in Houston area.