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!
]]>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.
]]>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.
]]>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.....
]]>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, 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.
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....