Author Topic: Mars sample return  (Read 13927 times)

Online speedevil

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Re: Mars sample return
« Reply #40 on: 06/14/2018 12:23 AM »
Is there any chance that Archaea come from Mars and Bacteria come from Earth? Is it known why Archaea and Bacteria split into two different kingdoms?
None whatsoever.
While being quite different, they share an enormous amount of common machinery, to the point they absolutely have to have a universal common ancestor.

Offline hop

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Re: Mars sample return
« Reply #41 on: 06/14/2018 02:06 AM »
The other thing I was thinking about is that it would be a good idea to put a few scientific instruments on the fetch rover. 
Even the best case scenarios for MSR look like budget busters, so I'd be pretty surprised if the fetch rover had much of a dedicated science payload.

Offline Don2

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Re: Mars sample return
« Reply #42 on: 06/14/2018 03:45 AM »
None whatsoever.
While being quite different, they share an enormous amount of common machinery, to the point they absolutely have to have a universal common ancestor.

So a Martian organism that evolved independently is not going to share common machinery with a Bacteria or an Archaea. Even if they all look the same under a microscope, once you start applying modern biochemistry you could be absolutely sure that you could tell Martian life from Earth life. It seems to me that if you can distinguish Bacteria from Archaea, then it ought to be easy to distinguish Earth life from Martian. As long as they evolved independently. If panspermia works, then Bacteria, Archaea and Martians will all share a common ancestor and have some common machinery. That would make it harder to distinguish Martian life from contamination from Earth.

All of the above has implications for planetary protection. I think NASA worries too much about it.

Offline Star One

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Re: Mars sample return
« Reply #43 on: 06/14/2018 05:54 AM »
None whatsoever.
While being quite different, they share an enormous amount of common machinery, to the point they absolutely have to have a universal common ancestor.

So a Martian organism that evolved independently is not going to share common machinery with a Bacteria or an Archaea. Even if they all look the same under a microscope, once you start applying modern biochemistry you could be absolutely sure that you could tell Martian life from Earth life. It seems to me that if you can distinguish Bacteria from Archaea, then it ought to be easy to distinguish Earth life from Martian. As long as they evolved independently. If panspermia works, then Bacteria, Archaea and Martians will all share a common ancestor and have some common machinery. That would make it harder to distinguish Martian life from contamination from Earth.

All of the above has implications for planetary protection. I think NASA worries too much about it.

Not if they both had a common ancestry. Earth and Mars are consistently sharing material, it didnít suddenly stop.

Offline Don2

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Re: Mars sample return
« Reply #44 on: 06/14/2018 07:15 AM »

Not if they both had a common ancestry. Earth and Mars are consistently sharing material, it didnít suddenly stop.

If panspermia ever happened, it would have been most feasible in the early solar system. Mars and Earth at than time would have had some places that had similar environments. At this point the environments are too different. If any habitable regions remain on Mars they are very small. And Earth has an oxygen atmosphere, which is likely toxic to any organism that isn't adapted to it. Oxygen is toxic to most primitive life forms. So I don't think that panspermia has happened recently.

Even if Martian and Earth organisms had a common ancestor, the environment on Mars would have lead to the evolution of distinctively Martian organisms which would have some unique features. DNA analysis would  identify the Martians.

Offline Don2

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Re: Mars sample return
« Reply #45 on: 06/14/2018 07:26 AM »
Even the best case scenarios for MSR look like budget busters, so I'd be pretty surprised if the fetch rover had much of a dedicated science payload.

I think that an APXS, an IR spectrometer and a microscopic imager are all small and cheap as instruments go. I agree that budget pressures will be severe, but the fetch rover will have years of useful life left after it has completed its primary mission.

There is also a case that adding anything that isn't strictly needed for sample return could open Pandora's box and lead to a cost explosion as more stuff is added. The is a case for being very focused.

Offline RonM

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Re: Mars sample return
« Reply #46 on: 06/14/2018 04:39 PM »
Even the best case scenarios for MSR look like budget busters, so I'd be pretty surprised if the fetch rover had much of a dedicated science payload.

I think that an APXS, an IR spectrometer and a microscopic imager are all small and cheap as instruments go. I agree that budget pressures will be severe, but the fetch rover will have years of useful life left after it has completed its primary mission.

There is also a case that adding anything that isn't strictly needed for sample return could open Pandora's box and lead to a cost explosion as more stuff is added. The is a case for being very focused.

The fetch rover will be going over the same territory as the rover that left the samples. Might not be worth the money having instruments other than cameras to do a second look. The fetch rover will need cameras to navigate and pickup sample containers. Comparing with previous pictures to see how things have changed would be useful.


Offline Don2

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Re: Mars sample return
« Reply #47 on: 06/15/2018 08:44 AM »

The fetch rover will be going over the same territory as the rover that left the samples. Might not be worth the money having instruments other than cameras to do a second look. The fetch rover will need cameras to navigate and pickup sample containers. Comparing with previous pictures to see how things have changed would be useful.

Two of the top sites, Jezero Crater and NE Syrtis are within about 40km of each other. So it would be possible for a fast rover to drive to the site that had not been explored.  Jezero Crater is a crater lake with a delta, while the NE Syrtis site has diverse minerals. The whole region seems to have a lot of scientific interest. I think there would be plenty for the fetch rover to do. Curiosity is nowhere near done with Gale Crater after 6 years.

The fetch rover will only have 240 days to do the sample collection mission, so it will have to travel an average of 100m per day. Once it is done with the samples, it will have about 10 years worth of life left with a drive capability of about 35 km per year. I think the scientists would make good use of it.

Offline vjkane

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Re: Mars sample return
« Reply #48 on: 06/15/2018 09:41 AM »
There are strong pressures to keep the fetch rover as simple as possible.  First, the rover will need to be very light; I believe that the current target is 125kg (Oppy is 180kg and ExoMars rover is ~425kg).  There will be a lot of pressure to keep it as simple as possible, which still requires a great deal of autonomy as well as a system to pick up the sample tubes and place them in a storage container.  Replicating the MER arm instruments would add a lot of complexity to the sample arm head

Any science instruments add complexity (as well as mass) so I'm betting that instruments will be kept off.  That said having the rover simply visit locations and image them with its cameras would still provide valuable scientific observations and ground truth for orbital observations.

Also, the highly capable Mars 2020 rover likely will have 10 years on its own to explore the region.  The fetch rover could be sent in a different direction to visit different locals.

Offline Star One

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Re: Mars sample return
« Reply #49 on: 06/15/2018 11:58 AM »
There are strong pressures to keep the fetch rover as simple as possible.  First, the rover will need to be very light; I believe that the current target is 125kg (Oppy is 180kg and ExoMars rover is ~425kg).  There will be a lot of pressure to keep it as simple as possible, which still requires a great deal of autonomy as well as a system to pick up the sample tubes and place them in a storage container.  Replicating the MER arm instruments would add a lot of complexity to the sample arm head

Any science instruments add complexity (as well as mass) so I'm betting that instruments will be kept off.  That said having the rover simply visit locations and image them with its cameras would still provide valuable scientific observations and ground truth for orbital observations.

Also, the highly capable Mars 2020 rover likely will have 10 years on its own to explore the region.  The fetch rover could be sent in a different direction to visit different locals.

Will this total mission be the heaviest payload ever sent to Mars?

Offline Don2

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Re: Mars sample return
« Reply #50 on: 06/16/2018 12:45 AM »

Will this total mission be the heaviest payload ever sent to Mars?

So, from the 2010 mission concept study:

Lander mass = 554 kg
Sample return rocket mass = 300 kg
Fetch rover mass = 157 kg
(All these masses include the reserve. Without reserve the rover is 110 kg)

I assume that you have to add those together to get the total landed mass of 1011 kg.

That compares to 899 kg for Curiosity. So yes, it will be the heaviest payload ever sent to Mars.

They plan to use the same landing system as for MSL. Skycrane capability is quoted at 1050 kg, so they are getting close to the limits of the Skycrane.

Total cost was estimated at 2.5bn(2015 $)

Offline Star One

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Re: Mars sample return
« Reply #51 on: 06/16/2018 09:56 AM »

Will this total mission be the heaviest payload ever sent to Mars?

So, from the 2010 mission concept study:

Lander mass = 554 kg
Sample return rocket mass = 300 kg
Fetch rover mass = 157 kg
(All these masses include the reserve. Without reserve the rover is 110 kg)

I assume that you have to add those together to get the total landed mass of 1011 kg.

That compares to 899 kg for Curiosity. So yes, it will be the heaviest payload ever sent to Mars.

They plan to use the same landing system as for MSL. Skycrane capability is quoted at 1050 kg, so they are getting close to the limits of the Skycrane.

Total cost was estimated at 2.5bn(2015 $)

I am assuming Atlas V will be out of the running by then as will DIVH and it will be straight fight of FH against Vulcan for the launcher.

Online Blackstar

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Re: Mars sample return
« Reply #52 on: 06/16/2018 10:57 AM »

Will this total mission be the heaviest payload ever sent to Mars?

So, from the 2010 mission concept study:

Lander mass = 554 kg
Sample return rocket mass = 300 kg
Fetch rover mass = 157 kg
(All these masses include the reserve. Without reserve the rover is 110 kg)

I assume that you have to add those together to get the total landed mass of 1011 kg.

That compares to 899 kg for Curiosity. So yes, it will be the heaviest payload ever sent to Mars.

They plan to use the same landing system as for MSL. Skycrane capability is quoted at 1050 kg, so they are getting close to the limits of the Skycrane.

Total cost was estimated at 2.5bn(2015 $)

All of which is OBE. We had that study done for the decadal survey. There's new work being conducted now and some of the tech decisions have been made or are about to be made.

Offline Don2

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Re: Mars sample return
« Reply #53 on: 06/16/2018 09:37 PM »

All of which is OBE. We had that study done for the decadal survey. There's new work being conducted now and some of the tech decisions have been made or are about to be made.

OBE? But it's OMHD! ;)

Looking at a fairly recent MEPAG presentation I notice that the sample return capsule has gone from 5 kg to 12 kg , and the return rocket (NASA calls this the MAV)  has switched from a proven solid to some kind of novel hybrid solid design. 12 kg seems like a lot of packaging for under 1 kg of sample, and I don't love the idea of developing a new rocket motor technology for the sample return mission.  I'm guessing the growing mass of the sample capsule has forced this switch?

Offline zhangmdev

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Re: Mars sample return
« Reply #54 on: 06/16/2018 11:32 PM »

Looking at a fairly recent MEPAG presentation I notice that the sample return capsule has gone from 5 kg to 12 kg , <snip> 12 kg seems like a lot of packaging for under 1 kg of sample<snip>

Do you mean the mass of Orbiting Sample (OS) is increased to 12 Kg? That is a huge increase.

The following plan may be old, but

https://trs.jpl.nasa.gov/bitstream/handle/2014/13724/00-0092.pdf?sequence=1

The OS is another very highly constrained system. It is made up of two pieces, the sample canister (SaC) and the power structure. This sphere must survive in orbit around Mars for 6 years. The power structure constains solar cells that provide power to a beacon that allows it be found by the orbiter, as well as corner cubes so that the LIDAR on the orbiter can detect it.

I think the packaging part is not that simple. And the actual samples are less than 500 g.

Online Blackstar

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Re: Mars sample return
« Reply #55 on: 06/17/2018 02:06 AM »
return rocket (NASA calls this the MAV)  has switched from a proven solid to some kind of novel hybrid solid design.

They've been testing the rocket motors for months now. The technology is proven.

Offline Dalhousie

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Re: Mars sample return
« Reply #56 on: 06/17/2018 06:52 AM »
There are strong pressures to keep the fetch rover as simple as possible.  First, the rover will need to be very light; I believe that the current target is 125kg (Oppy is 180kg and ExoMars rover is ~425kg).  There will be a lot of pressure to keep it as simple as possible, which still requires a great deal of autonomy as well as a system to pick up the sample tubes and place them in a storage container.  Replicating the MER arm instruments would add a lot of complexity to the sample arm head

Any science instruments add complexity (as well as mass) so I'm betting that instruments will be kept off.  That said having the rover simply visit locations and image them with its cameras would still provide valuable scientific observations and ground truth for orbital observations.

Also, the highly capable Mars 2020 rover likely will have 10 years on its own to explore the region.  The fetch rover could be sent in a different direction to visit different locals.

You can learn a lot scientifically from the Navcams, system environmental sensors, power delivered from panels, and power consumption by motors vs distance travelled.
"There is nobody who is a bigger fan of sending robots to Mars than me... But I believe firmly that the best, the most comprehensive, the most successful exploration will be done by humans" Steve Squyres

Offline vjkane

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Re: Mars sample return
« Reply #57 on: 06/17/2018 07:22 AM »

Looking at a fairly recent MEPAG presentation I notice that the sample return capsule has gone from 5 kg to 12 kg , and the return rocket (NASA calls this the MAV)  has switched from a proven solid to some kind of novel hybrid solid design. 12 kg seems like a lot of packaging for under 1 kg of sample, and I don't love the idea of developing a new rocket motor technology for the sample return mission.  I'm guessing the growing mass of the sample capsule has forced this switch?
I believe that a big driver is finding a fuel that could take long periods of cold temperatures. 
« Last Edit: 07/25/2018 05:30 AM by Lar »

Offline zhangmdev

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Re: Mars sample return
« Reply #58 on: 06/17/2018 07:36 AM »
Is the two-stage, solid motor-based MAV still the baseline design?

And ATK is developing a new propellant formulation specifically for the MAV

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160008023.pdf

Offline Don2

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Re: Mars sample return
« Reply #59 on: 06/17/2018 09:37 AM »
OK, this is from the Feb 20 2018 MEPAG meeting.

https://mepag.jpl.nasa.gov/meeting/2018-02/04_Edwards_MSRMidDecadal_MEPAG_VM1.pdf


It states the Orbiting Sample is mass =< 12 kg, diameter =< 28cm and contains 31 tube slots and 2 sample air tanks.

On the rocket is says the 2 stage solid motor is no longer the baseline design.  They have switched to a single stage to orbit hybrid using MON as the oxidizer. Gross lift off mass is about 300 kg. It is the SP7 hybrid motor developed by MSFC. The motor and the thrust vector control system are listed as "Technology development underway." As of March 2018 it seems they had not done a full duration burn.

Using this hybrid motor saves about 100 kg relative to using a 2 stage solid.


I believe that a big driver is finding a fuel that could take long periods of cold temperatures. 
 

RTGs put out plenty of heat, they could use one of those to keep the rocket warm. The hybrid motor does have better low temperature performance.

« Last Edit: 06/17/2018 09:40 AM by Don2 »

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