Mars Direct; Mars Semidirect; Design Reference Mission. Need Updating?

SpaceNut · 2017-04-10 20:35:16

Loius the wattage in post # 144 is incorrect as thats what it can recieve on earth for that given area less the solar panel efficency will not make that and if that is watt hours then we are looking at what has been stored for consumption. That would if we knew the effieciency tell us how many usefull hours were used to charge the storage batteries.

As in post # 145 I to would love to drop a nuclear reactor on mars but thats not with in the mass capability for mars and may not for several ore decades at the rate Nasa and others are going to it.

The solar cell panels could be arranged into a different type of fan system simular to something simular to this next image...

I also came accross another concentrating technique that looks like a cone...

http://inhabitat.com/v3solars-photovolt … -day-long/

a 20x solar concentration on a flat, static solar panel then “the temperature quickly reaches 260 degrees F, the solder melts within ten seconds, and the PV fails. With the same concentration on the Spin Cell, the temperature never exceeds 95 degrees F.”
The one meter-diameter cones feature a layer of hundreds of triangular photovoltaic cells positioned at an angle of 56 degrees, encased in a “static hermetically-sealed outer lens concentrator.” The photovoltaic cone spins with the assistance of a “small amount” of its own solar-generated power which feeds a Maglev system, intended to reduce the noise generated by the cones as well as any required maintenance.

Sounds to me that this solves the power issue...

louis · 2017-04-11 04:21:54

Wow, hadn't seen that PV cone before. It's very interesting. I was struggling with why it has to spin...was that to keep the temperature down?

These could indeed be a win on Mars although I suspect mass might still be more than lightweight, more conventional PV. But if mass is not such an issue, then these units look like they might be more easy to put in place and maintain. Reducing the PV field area of 10,000 sq metres to 500 sq. metres (assuming you are generating 20x the amount of power) would be a boon, although it appears you would have to strategically arrange them to avoid shadowing effects so in terms of the amount of ground covered, I am not sure in reality how that would work. What sort of configuration would work best?

SpaceNut wrote:

Loius the wattage in post # 144 is incorrect as thats what it can recieve on earth for that given area less the solar panel efficency will not make that and if that is watt hours then we are looking at what has been stored for consumption. That would if we knew the effieciency tell us how many usefull hours were used to charge the storage batteries.
As in post # 145 I to would love to drop a nuclear reactor on mars but thats not with in the mass capability for mars and may not for several ore decades at the rate Nasa and others are going to it.
The solar cell panels could be arranged into a different type of fan system simular to something simular to this next image...
http://upload.ecvv.com/upload/Product/2 … 640491.jpg
I also came accross another concentrating technique that looks like a cone...
http://inhabitat.com/v3solars-photovolt … -day-long/
http://assets.inhabitat.com/wp-content/ … cell-3.jpg
a 20x solar concentration on a flat, static solar panel then “the temperature quickly reaches 260 degrees F, the solder melts within ten seconds, and the PV fails. With the same concentration on the Spin Cell, the temperature never exceeds 95 degrees F.”
The one meter-diameter cones feature a layer of hundreds of triangular photovoltaic cells positioned at an angle of 56 degrees, encased in a “static hermetically-sealed outer lens concentrator.” The photovoltaic cone spins with the assistance of a “small amount” of its own solar-generated power which feeds a Maglev system, intended to reduce the noise generated by the cones as well as any required maintenance.
Sounds to me that this solves the power issue...

louis · 2017-04-11 04:34:57

Spacenut,

That's the MIT figure and I think it must be right. In fact it's very low...10 watts average per square metre of PV panel (they have an area of 10,000 square metres). I presume that is the average across an average sol (or, better, a half sol's worth of sunlight). That's extremely modest, probably because the efficiency is v. low in ultra lightweight PV. Presumably you have to then use a portion of the average 100 Kws during the day to store in chemical batteries, heat up night storage heaters and so on. So, effectively, you might has something like 60-70 Kws during sol-light .

SpaceNut wrote:

Loius the wattage in post # 144 is incorrect as thats what it can recieve on earth for that given area less the solar panel efficency will not make that and if that is watt hours then we are looking at what has been stored for consumption. That would if we knew the effieciency tell us how many usefull hours were used to charge the storage batteries.
.

SpaceNut · 2017-04-11 19:30:34

Mars for that panel area is just 43% of that number so it really is not as good as we would like.
The cone shaped cells do look nice but they come with the mass penalty to make up for getting the energy. What is not really said is the type of cells with in the cone or of the cell efficiency before being placed within a optical concentrator....

louis · 2017-04-12 04:00:49

I think if you look back at the paper, you'll see they have taken account of insolation levels on Mars.

SpaceNut wrote:

Mars for that panel area is just 43% of that number so it really is not as good as we would like.
The cone shaped cells do look nice but they come with the mass penalty to make up for getting the energy. What is not really said is the type of cells with in the cone or of the cell efficiency before being placed within a optical concentrator....

SpaceNut · 2017-04-16 18:05:19

3015 wrote:

Louis, the panels described in the paper are very light but they don't pack densely. The paper cited in the one you linked (with the 0.063 kg/m^2 panels) lists a volume of 0.055 m^3 per 35.3 m^2 of panel area. So for 10,000 m^2 of panels the volume would be 15.6 m^3.

louis · 2017-04-17 07:23:55

Thanks for the correction SpaceNut.

SpaceNut wrote:

3015 wrote:
Louis, the panels described in the paper are very light but they don't pack densely. The paper cited in the one you linked (with the 0.063 kg/m^2 panels) lists a volume of 0.055 m^3 per 35.3 m^2 of panel area. So for 10,000 m^2 of panels the volume would be 15.6 m^3.

SpaceNut · 2017-04-17 17:58:20

I did look again at the universtoday page article and the thin film rolled out panels with the array positioned at 25° north, measuring 100×100 metres, 100 kilowatts generated.

I solved it for the single panel amount recieved. 100kw/10km= 10Wm^2 which really sucks for performance and then when you look at them laying flat on the ground not aligned so no wonder they are horrible. As we should be at about 65Wm^2 for the 15% efficency aligned towards the sun perpendicular.

The MIT paper is talking about panels that are simular to the ISS units for how they are created as a ultra-light amorphous silicon rollout blanket array. When using Li-ion have a mass-specific energy density of 150Wh/kg and a
volume-specific energy density of 270kWh/m3.

A night time power of 12kW is assumed to be enough to sustain six crewmen. The day time power requirement is not enforced until the sun is 12' above the horizon. Which limits the charging time to way less than the 12 hour of a sunny day.

The issue with the battery notation is that Wh does not take into account the cell voltage to which this number is being given. Typical Li-ion cell is 3.7 v but using that we still do not have the ampere that can be draw from the battery pack but the charging time is not at the same rate of discharge either. Need to dig the document for more numbers.....

Oldfart1939 · 2017-05-21 12:30:53

This seems to mirror another recent post...

Oldfart1939 · 2017-05-21 13:26:58

We really should begin taking advantage of the progress in orbital rendezvous and orbital construction (actually join-up of components launched separately), to enhance the original Zubrin concepts, not replace them.

kbd512 · 2017-05-21 21:28:47

Oldfart1939,

The key concepts from Mars Direct were:

1. Super Heavy Lift Rockets

Falcon Heavy / New Glenn / Vulcan Heavy all have TMI capabilities in the 15t to 25t range. Super Heavy Lift Rockets were required for 1970's to 1990's era life support, power, and power storage hardware. Current or near-production ready commercial technologies blow right past what was available back then in terms of affordability (cost per ton delivered) and sustainability (launch cadence capability). Current generation life support technologies are not nearly as heavy or power intensive, either, and far more efficient in terms of closing the loop. Therefore, no requirement exists for rockets with TMI capabilities past 25t.

2. Habitat Module Lander - Cygnus or Dragon 2 with inflatable

The small aluminum cans and inflatables beat ISS modules and upper stage propellant tanks for general purpose utility. If NASA wants a new space station, then inflatables still provide more pressurized volume, more ballistic protection, and more radiation protection than aluminum cans on a pound-for-pound basis. Aluminum cans are a well-understood technology for aerospace engineers to work with, which is why I suggested using Cygnus with liners and Dr. Zubrin suggested using Dragon 2 with a deployable inflatable for storage. An all-inflatable architecture still requires more testing, but inflatables have been in space for years now in the low Earth orbit shooting gallery environment and no adverse qualities have been noted, with respect to aluminum cans.

3. Deployable Heat Shield

HIAD (up to 20t or so) and ADEPT (20t+) are the way forward for crewed Mars missions. PICA / AvCoat / HRSI / RCC are all useful technologies for Earth reentry, but weigh too much and provide too high ballistic coefficients for Mars reentry with payloads in the tonnage ranges useful for crewed missions. We're supplementing existing heat shield technologies with lower mass, lower ballistic coefficient technologies created specifically for Mars reentry. To a point, that point being the G-loading the crew can survive, maximum drag (low ballistic coefficient) is desirable to slow down as fast as possible and as high up in the atmosphere as possible so that subsonic retro-propulsion can be employed to brake and soft land.

4. Surface Nuclear Power Source

SAFE-400 and now Kilopower provide 24/7 electrical output in volumetrically small packages, even if they're heavy. Right now, available solar and battery technology would be just as heavy. That's changing, but it's the way things are right now. Once the energy density problem that Lithium-ion batteries have is solved with Graphene-based batteries, it'll be the other way around until we get into the MW range, at which point nuclear power density still beats solar and battery power. By the time we're ready to go, a nuclear reactor may just be a back-up power source that's only activated in emergencies. Ultimately permanent batteries like Silicon-Graphite and homopolar generators will replace solar panels and Lithium-ion batteries as the primary power source for exploration missions and fission reactors remain the only viable power source when the power requirements creep into the MW range. In the multi-MW range, there's simply no contest between nuclear and solar.

5. In-Situ Resource Utilization

Apart from astronauts, no other travelers take all their oxygen and water with them. It's necessary in transit because there are no sources of oxygen or water, but once you arrive, both are available. If there's a future for humans on Mars, then these two essentials must be made available using local resources. Earth return is also easier to accomplish with propellant production on Mars. It is imperative that H2O, LOX, LN2, and LCH4 production plants be developed to assure surface sustainability and Earth return. Storable chemical propellants like NTO/MMH are within the realm of feasibility in the interim for Earth return, but every kilo of rocket propellant delivered to the surface is not a kilo of food, water, or life support equipment. Any rocket propellants shipped from Earth will be the most expensive rocket propellants known to man, not as a function of production cost, but delivery costs. Apart from a handful of exploration missions, there's no way we can sustainably ship $50K/kg rocket fuel.

6. Long Range Rover

Good surface mobility is closely associated with good survivability and the ability to truly explore. To avoid impacting any assets already on the surface of Mars, it's a really good idea to land at least several kilometers, if not ten or more kilometers away. There must be a durable and radiation-protected surface transport vehicle available to transport humans and cargo to and from landing sites, ascent sites, habitation sites, and exploration sites.

7. Closed-Loop Life Support

Last but most importantly, closed-loop or near closed-loop life support is a diamond hard requirement for long duration space exploration missions of any kind. This is presently the highest hurdle to clear, the most intractable problem to solve, and the primary reason why we can't go to Mars right now. The funding wasted on Orion should be directed towards developing this technology set, which is the most important of them all. All other technologies are either ready or nearly ready for prime time, but this technology most definitely is not ready. This point can't be hammered home hard enough. If this technology set is not reliable and nearly maintenance-free, we're not going anywhere, period, end of story. ISS life support technology is too heavy, too power intensive, and too maintenance intensive for use on Mars.

Oldfart1939 · 2017-05-21 21:38:39

kbd512 wrote:

Oldfart1939,
The key concepts from Mars Direct were:

7. Closed-Loop Life Support
Last but most importantly, closed-loop or near closed-loop life support is a diamond hard requirement for long duration space exploration missions of any kind. This is presently the highest hurdle to clear, the most intractable problem to solve, and the primary reason why we can't go to Mars right now. The funding wasted on Orion should be directed towards developing this technology set, which is the most important of them all. All other technologies are either ready or nearly ready for prime time, but this technology most definitely is not ready. This point can't be hammered home hard enough. If this technology set is not reliable and nearly maintenance-free, we're not going anywhere, period, end of story. ISS life support technology is too heavy, too power intensive, and too maintenance intensive for use on Mars.

Wholeheartedly concur. The discussion of water and habitat, in addition to breathable atmosphere should be our major topics of discussion.

As stated on my other thread: Protection from elements with breathable atmosphere trump all other problems, followed by food and water.

Yeah, I've only read The Case for Mars maybe 7 or 8 times. Ditto entering Space, and not as many for the small Mars Direct book.

Oldfart1939 · 2017-05-21 21:45:37

kbd512-

I was simply pointing out that the existing throw mass to Mars using a single Falcon Heavy launch is strictly limited. If we're not going to wait around another 30 years or so, we need to get focused on GOING TO MARS!

SpaceNut · 2017-05-22 16:55:13

Closed-Loop Life Support is not happening and you can look to how we live on earth as without the natural resources we can not exist. So thinking that we will survive on what we take is also not going to change that regardless of the efficiency that we can achieve we will always need input into life support when living on mars. All that we can hope for is a crew that can control events within there grasp and situations. To understand this we only need to look at the isolation that the ISS commits on its occupents as this is not all that far from where mars is. That said we know the resources of the iss and of its efficiencies and of its resuply that it takes. To go to mars with these same simular devices will not change the outcome needed for man to survive.
Can we improve the odds of survival, hell yes with more preloading of what we need in processing equipment which includes recovery, food, water, and power....which will allow us to improve on the shelter while we stay and explore. The science of the first mission timewise is not all that different than what we spend on the iss for its crew to survive as part of that survival is the health of the crew while we are there.
Which brings me to what could result in rationing of these very same life support items if any thing should go wrong.
Being prepared will save life and make it so that we can keep going to mars.

https://www.energy.gov/ne/nuclear-react … r-reactors

http://www.world-nuclear.org/informatio … ctors.aspx

RobertDyck · 2017-05-22 20:40:31

Robert Zubrin wrote in his book "The Case for Mars" that we should go with life support that existed at that time. Actually, at the time he first pitched Mars Direct to NASA, in 1990, which was before that book. He argued life support was not perfect, but he complained that if we waited for the 95% efficient oxygen and water recycling that NASA wanted at that time, then it would be the 21st century before we're ready to go! Oops! Ever since year 2001 I've been saying "Oops! It is the 21st century! Can we go now?!?!?" Actually, NASA reports that life support on ISS right now recycles oxygen and water with 93% efficiency. I've argued for a couple components to be added to what's on ISS right now. Not replace anything, just add to it. This should meet or exceed the 95% that NASA said in 1990 it wants before going to Mars.

kbd512 · 2017-05-22 21:19:34

We have already demonstrated 98% efficient water recycling and in a few more years and Paragon should have that up to 99%. CAMRAS is not quite that efficient, but with MOXIE replacing atmospheric losses, it really doesn't have to be. The losses are so small that they're measured in pounds of O2 and H2O over the course of a year. The power requirements for CAMRAS, IWP, and MOXIE are well within what solar panels and batteries can deliver. Heck, on Mars a 300We RTG could provide the power required by these systems and thermal output from the RTG could push refrigerant through a thermal control loop in conjunction with a suitable cold plate. If we send our explorers in pairs, then we can do this in about 10 years. If we insist on sending half a dozen or more people in one spacecraft, we'd have to wait longer.

SpaceNut · 2017-05-23 18:00:59

Slide 5 of this link does a nice job of showing all types of power levels to duration...
5595_files/Electrical Power Subsystem_v2.ppt

SpaceNut · 2018-11-25 17:36:25

So how do we update when SLS is what Nasa is building for a re-sprite to the moon

SpaceNut · 2019-12-30 21:12:47

seems that we are looking at options for how to improve the energy to make methane versus using high pressure hydrogen and super chilling it before use.
I am also looking at insitu tank creation on mars for how to get more mass to mars.

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