Author Topic: MCT Speculation and Discussion Thread 4  (Read 621408 times)

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #340 on: 07/24/2015 07:19 AM »
We know now first hand that they are not aiming low. 2-5 reuses would only help to make their competetive situation better which is already very good.

100 or more is what they need to get prices anywhere near what Elon Musk has proposed for his Mars architecture.

Offline marcon

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Re: MCT Speculation and Discussion Thread 4
« Reply #341 on: 07/24/2015 09:09 PM »
For all non-German speakers:
[...]
(just to elaborate on what was mentioned above)

Thx Marcon. I thought about writing a translated transcript but decided its not worth it since he doesnt mentions anything new. Your summary is way better than either nothing or a transcript. Thx.
Thank you. I usually do enjoy reading transcripts done by other people ;-), but you are right, there wasn't really anything new.

It is such a pity they didn't ask Koenigsmann more personal questions about the early days.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #342 on: 07/25/2015 02:02 AM »
We know now first hand that they are not aiming low. 2-5 reuses would only help to make their competetive situation better which is already very good.


Are you referring to some new information?  If so it should get posted in http://forum.nasaspaceflight.com/index.php?topic=37839.0

Offline Pipcard

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Re: MCT Speculation and Discussion Thread 4
« Reply #343 on: 08/13/2015 10:48 PM »
Will the MCT need a nuclear reactor? Zubrin thought that Mars Direct's ERV would need a 100 kW nuclear reactor to power the ISRU plant.

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #344 on: 08/14/2015 01:41 AM »
NO, even Zubrins idea's were for a reactor to be cargo not integral to the vehicle.

Offline spacenut

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Re: MCT Speculation and Discussion Thread 4
« Reply #345 on: 08/14/2015 02:01 AM »
Again, using existing solar panels on Mars, how big an area would 100kw of solar panels cover?  Of course it will only work effectively 8-10 hours a day whereas a small nuke unit will go 24-7. 

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #346 on: 08/14/2015 05:46 AM »
Again, using existing solar panels on Mars, how big an area would 100kw of solar panels cover?  Of course it will only work effectively 8-10 hours a day whereas a small nuke unit will go 24-7.

Insolation on Mars will be roughly 400W/mē. Calculate with 25% efficiency for low efficiency but very low weight solar foils and you get 100W/mē. That's 1000mē for 100kW peak output. More if you want that power for 8-10 hours/day.

Offline Vultur

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Re: MCT Speculation and Discussion Thread 4
« Reply #347 on: 08/14/2015 05:52 AM »
Realistically you'd probably also want more to allow for high atmospheric opacity during dust storms. But thin films can be VERY thin and light.

Offline oldAtlas_Eguy

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Re: MCT Speculation and Discussion Thread 4
« Reply #348 on: 08/14/2015 09:45 PM »
Add lightweight reflectors which can also be used to cover the array during dust storms which will more than double the isolation to possibly as high as 1000w/m^2 for the array itself. So the array with its fold out reflectors would need to be 400m^2 for 100kw for about a 30% equivalent daily power level. so increase the size of the arrays to 1500m^2 to handle the short daylight charging duration where the panels peak output is 375kw. With a good lithium rechargeable batteries you may get as good as up to 100kw continuous power. 1500m^2 is a set of arrays that folded would be 30m X 50m. Unfolded they would cover an area of 70m X 50m. That is actually a fairly large area about twice the size of a football field. So besides the panels there will be a need for structures to mount the panels and wiring for connecting the panels back to the power management systems (batteries and power conditioners). All of which adds weight. At 10kg per m^2 (that includes the reflectors) just the arrays will weigh 15mt. Now add structures wiring and storage batteries and your up to something around 50mt for a 24/7 100kw power system.

Offline Vultur

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Re: MCT Speculation and Discussion Thread 4
« Reply #349 on: 08/14/2015 11:42 PM »
10kg per m^2 for just the arrays sounds really high given modern thin films.

Thin films just placed on the ground would have lower efficiency per square meter due to dust and lack of reflectors... but probably significantly better per kilogram.

The cells in IKAROS were 25 micrometers thick - if they were amorphous silicon, that's something like 58 grams per m^2!

It might need to be somewhat thicker on Mars due to wind, but even so, I think you could do way better than 10kg per m^2.

Offline Jcc

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Re: MCT Speculation and Discussion Thread 4
« Reply #350 on: 08/14/2015 11:58 PM »
10kg per m^2 for just the arrays sounds really high given modern thin films.

Thin films just placed on the ground would have lower efficiency per square meter due to dust and lack of reflectors... but probably significantly better per kilogram.

The cells in IKAROS were 25 micrometers thick - if they were amorphous silicon, that's something like 58 grams per m^2!

It might need to be somewhat thicker on Mars due to wind, but even so, I think you could do way better than 10kg per m^2.

For an initial robotic mission, thin film arrays that can unroll themselves are probably the best bet. With human labor, simple reflectors could be added that require people to assemble them to minimize weight and complexity. If a reflector weighs more than the array per sq meter, it's not worth using it.

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #351 on: 08/15/2015 05:26 AM »
Reflectors may not be that much lighter than thin film arrays. More importantly they don't work well during dust storms. Overall it is IMO better to increase solar cell array size.

Initially they would be deployed flat on the ground which is easy to automate. When humans arrive they may go on frames which gets them into the best angle and minimizes dust accumulation.

Offline Jimmy Murdok

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Re: MCT Speculation and Discussion Thread 4
« Reply #352 on: 08/15/2015 12:00 PM »
If you want high solar panels you can use poles and ropes, no need of heavy structures. The weight will come more from good uv protection than the panel itself. No need of reflectors just more light panels.

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #353 on: 08/15/2015 12:39 PM »
The weight will come more from good uv protection than the panel itself.

Not necessarily. UV protective coating can be thin and invisible. I learned that when I built a roof for my terrace. The transparent polycarbonate panels come with an UV coating on one side. You don't even see that. The panels need a marking for the side that goes up. If you mount them wrong side up they don't last.

Offline spacenut

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Re: MCT Speculation and Discussion Thread 4
« Reply #354 on: 08/15/2015 12:56 PM »
So, the first few MCT's might have to be expendable or will have to stay until everything is set up for fuel production.  It would probably take two or more to just land and maybe using robotics deploy the first solar panels and power station for fuel production and power for habitats.  Then the passengers can come and start setting things up that cannot be done with robot deployment.  So it might be months before the first MCT can return.   

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #355 on: 08/15/2015 01:17 PM »
So it might be months before the first MCT can return.

I don't see less than a full cycle, so more than two years, if everything goes right. But they would have consumables for twice that in case something goes wrong and replacements for fuel ISRU need to be sent.

This would be done with long time stays in mind from the beginning. Just remember Aldrin. He proposes sending people without even the means in place to get them back and work that out later. I don't support that but see initial missions with 2 years or more on the surface of Mars as the way to go if you want to start a settlement.

Edit: Not that much is needed, assuming that at least water is available and air for breathing can be sourced locally. Inspiration Mars calculated with 300 or 500g per day per person. That may be too low. If you calculate 10 persons with 2kg/day/person that's  ~30t for four years. That much can be carried on the crew MCT.
« Last Edit: 08/15/2015 01:21 PM by guckyfan »

Offline Impaler

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Re: MCT Speculation and Discussion Thread 4
« Reply #356 on: 08/15/2015 06:06 PM »
It hinges on the mass of the ISRU equipment and power systems.  If a complete automated deployment turn-key system capable of refueling the MCT-Lander in 1 synod will fit within one such Lander then I see no reason to ever abandon any mechanically sound lander.

Rather you go right into propellant production, return the first vehicle and leave the ISRU equipment in place.  This achieves the two most important goals, 1) Have propellant in place before crew is risked, 2) Validate the entire round-trip flight of the vehicle before crew is risked.

The only reason to temporarily or permanently 'strand' an expensive vehicle on Mars is if the ISRU equipment is so massive that it needs to be broken-up over multiple landers, but all of my estimates show that it should easily fit within one landers 100 mT capacity (and finish in 1 synod), provided that the return propellant mass is not some absurd amount like 1000 mT.
« Last Edit: 08/15/2015 06:16 PM by Impaler »

Offline Burninate

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Re: MCT Speculation and Discussion Thread 4
« Reply #357 on: 08/15/2015 06:14 PM »
The weight will come more from good uv protection than the panel itself.

Not necessarily. UV protective coating can be thin and invisible. I learned that when I built a roof for my terrace. The transparent polycarbonate panels come with an UV coating on one side. You don't even see that. The panels need a marking for the side that goes up. If you mount them wrong side up they don't last.

Not that I know much about this, but hard UV straight from the Sun is rather different from the bit of it that gets through our atmosphere.

Offline guckyfan

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Re: MCT Speculation and Discussion Thread 4
« Reply #358 on: 08/15/2015 07:02 PM »
Not that I know much about this, but hard UV straight from the Sun is rather different from the bit of it that gets through our atmosphere.

Sure but I think we can make better coatings than the one on my panels without putting thick glass over the solar arrays.

Offline lamontagne

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Re: MCT Speculation and Discussion Thread 4
« Reply #359 on: 08/15/2015 07:31 PM »
It hinges on the mass of the ISRU equipment and power systems.  If a complete automated deployment turn-key system capable of refueling the MCT-Lander in 1 synod will fit within one such Lander then I see no reason to ever abandon any mechanically sound lander.

Rather you go right into propellant production, return the first vehicle and leave the ISRU equipment in place.  This achieves the two most important goals, 1) Have propellant in place before crew is risked, 2) Validate the entire round-trip flight of the vehicle before crew is risked.

The only reason to temporarily or permanently 'strand' an expensive vehicle on Mars is if the ISRU equipment is so massive that it needs to be broken-up over multiple landers, but all of my estimates show that it should easily fit within one landers 100 mT capacity (and finish in 1 synod), provided that the return propellant mass is not some absurd amount like 1000 mT.

About 700 metric tons.  So semi absurd  ;-)
One of the MCT will make a good storage tank.  It has the storage capacity required for the second MCT.  If you don't keep an MCT in place where will you store the fuel?  So the first MCT of all will stay in place, roll out large solar arrays to get power and produce and store fuel for the second ship's return. Or it could switch out with the second ship, as long as it leaves all the production equipment in place. 

Personally, I expect the first 2, possible the first 3 MCT to be entirely remote controlled and to not return.
How much energy does it take to extract the fuel from the air and water, and how quickly do we want to do it?  That is what fundamentaly sets the power required, isn't it?  So many many solar arrays at first, because there will not be a nuclear reactor developped in the next few years, unless things change dramatically on the energy front.


Here is a possible MCT propellant tank arrangement, CH4 and O2.






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