farmerben
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Posts posted by farmerben
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Methane fuel cells are available as well. They are crazy expensive though.
I'm actually designing a catamaran to take the Northwest Passage. I'm looking at the best way to power it and to heat the whole boat. Perhaps fuel cells could be built into the oven. You can cook on the heat generated by fuel cells. Open the oven door and blow a fan across it to heat the whole boat. Of course there are numerous approaches you could take for heat, the priorities are lightweight and fewest number of potential failure points.
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What is the weight to energy ratio of hydrogen fuel cells? I googled it but can't find simple off the shelf hydrogen fuel cells with their mass and energy output posted like the ones in KSP.
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Is an ocean planet really colonizable? How?
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Bezos loves KSP proof in taters video above.
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Most of the objects we are interested in have periapsis at the range of Pluto and beyond, namely balls of frozen water and ammonia which will help build an atmosphere on Mars. We should be able to find plenty of Kuiper belt objects with the inclination close to ideal already. 4000-5000 km/s of delta V should be more than adequate.
If you had a mass driver you might be better off flinging snowballs at mars thousands of times and letting the main comet go into interstellar space. This would allow you to adjust your aim. And if some of your shots miss by 1000 years it will not be bad for the Martians as small ice chunks will "burn up" in the atmosphere, where a giant comet might not.
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The scenario of deflecting a comet so it misses a planet is very different than deflecting one so it hits.
You want to do most of the pushing way out in Kuiper belt where velocity is slow. You have to maneuver the comet very precisely. So I think you need to land on the comet and have variable thrusters. Nuking it is not precise enough. The painting strategy might not be precise enough either.
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I think you need to use the comet itself as propellant.
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What is the best propulsion method to perturb a comet so it will impact Mars?
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Part C must be a vacuum filled Beryllium chamber. The other part can be an actively cooled helium sterling cycle engine. The electricity derived could support quite a lot of systems.
It's unclear whether the discs will be coated with U235 or some more exotic unobtanium. Americium or Curium might be better. This is because of high energy alpha particles interacting with the beryllium will excite neutrons driving it above criticality. And you want to a fissile material that has a large cross section for both fast and slow neutrons.
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I dunno what TRL means. I think the TWR is rather low. But ion thrusters are in the 5000s ISP range, so they are not quite up for interstellar voyaging.
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Quote
Rotating fuel reactor
A design by the Idaho National Engineering Laboratory and Lawrence Livermore National Laboratory[1] uses fuel placed on the surface of a number of very thin carbon fibres, arranged radially in wheels. The wheels are normally sub-critical. Several such wheels were stacked on a common shaft to produce a single large cylinder. The entire cylinder was rotated so that some fibres were always in a reactor core where surrounding moderator made fibres go critical. The fission fragments at the surface of the fibres would break free and be channeled for thrust. The fibre then rotates out of the reaction zone to cool, avoiding melting.
The efficiency of the system is surprising; specific impulses of greater than 100,000 s are possible using existing materials. This is high performance, although the weight of the reactor core and other elements would make the overall performance of the fission-fragment system lower. Nonetheless, the system provides the sort of performance levels that would make an interstellar precursor mission possible.
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Would carbon monoxide be the ideal fuel for a Mars direct style ISRU fuel system?
It gets and ISP of only 200s. So its half as powerful as methane or kerosene. But you only need 1/9 of the dV to go from surface to orbit.
The real question is can you the machinery to make carbon monoxide out of CO2 and separate the oxygen as well be made in a compact lightweight form?
You can also blend gaseous fuels (possibly). Wood gas is about half carbon monoxide and half hydrogen.
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It's not on my list of major concerns period. You could more than make up for the dose by eating less radioactive potassium, fewer fresh outdoor grown fruits and so on.
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For a mission we could do today. Land a stationary probe in the center of the caldera on Pavonis Mons. Equip it with high quality telescopic cameras and radar. You can scan the entire vertical surface looking for caves, and scanning the minerals as best you can from 20 km away.
The cliff walls of the caldera are over 150 km in circumference and 5 km high. Dust does not rest on vertical surfaces.
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42 minutes ago, Gargamel said:
First time I read SevenEves, I couldnt get into act III, just lost interest. Second time I read it, finished it, still didn’t like act III. Dunno, just didn’t enjoy it.
I know somebody else who said the same thing. I liked it even though its very implausible. Maybe I just like the concept of an orbital ring civilization.
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21 hours ago, magnemoe said:
Main problem is that tunnels are not quarries, quarries are put places there the rock is of uniform good quality. Tunnels is put places there you want tunnels.
Think long wire cutters are most common but you also have cutting blades like giant angle grinder or even giant chain saws for softer rocks. But in the quarries you have access to the rock from top and at least one side so you can cut blocks.
In an tunnel you have one angle of attack at least until you cut an initial opening.
Tunnels in rocks is made either by drilling and blasting, repeat or tunnel boring machines, first is best for hard rock or short tunnels later for long or soft stone or just gravel.
Now I wonder if water cutting jets could be useful, perhaps combined with explosives, drill deeper use an water jet to make an cavity, pump slurry explosives into them and set off.
People has been thinking of weird stuff like using cannons for drilling if tine critical like rescue missions or simply you have to close an major highway or rail line to start drilling so you want the phase to be fast. -
I enjoyed the Ender's Game novels as well, including the sequels. But by far my favorite author is Neal Stephanson.
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Pavonis Mons is an ideal spot for an agricultural city as well as other things. There is a deep crater to dome over and hold atmosphere. Natural rock will provide radiation shielding for all but a slice of sky. The center of the dome/crater could become agricultural while the habitations are carved into the walls of the crater. The other nice thing about Pavonis Mons is the rim is right on the equator so it an ideal spaceport, or a rail launched mass driver. All the spoil from excavating can be rolled down the slopes of the mountain to create tracks for mass driver/rail/road/electricity transport. The top of the mountain is above the height of many dust storms so cleaning the solar panels is relatively easier than at low elevation. Not sure about water. Water and air might have to be hauled in and continuously recycled. It makes more sense to grow your veggies in containers for water recycling and other reasons. Giant dehumidifiers will be needed to catch the moisture from plants and animals. The basic floor and walls of the crater can be left as bare rock. That is somewhat permeable to air and water. But allows you to be constantly working fresh ground.
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4 hours ago, darthgently said:
Interesting problem. How would the cutting head work? Blocks and slabs are normally cut off with plenty of room to work in an open quarry. How does cutting blocks or slabs work in a tunnel a few meters across?
Drill four pilot holes. Then use band saw to connect the holes. Then use a wedge to crack the back surface and extract a block.
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Tunneling would be more economical if the spoil was worth good money. Granite, Basalt, and even limestone blocks and slabs could easily sell for over $1000 ton. Conventional tunneling makes gravel which is only worth about $30 ton. A 3300% increase in spoil revenue is huge. It would financially make up for going slower.
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Modertoar’s Note: This thread is split off from the Bad Hall of Shame thread
You can now listen to The Mote in God's Eye and The Gripping Hand. Best aliens in all of Sci Fi.
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Maybe for 100 kg of xenon we could park it at L4.
Or better yet argon.
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Supposing you wanted to tunnel out a 1.2km asteroid, there is not much surface gravity to hold down the dust you make from excavating.
It might be easy to dig however since lifting spoil costs almost no energy. A good rotary head could grind and fling dust. A little puff of gas now and then could help blow out the hole. The thing is you need a tent like superstructure to catch your dust and let it pile up on the surface.
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https://www.space.com/nuclear-fission-neutron-stars-heavy-elements-gold
Theorized a long time ago, now there is some evidence for it. Heavy elements are created when neutron stars collide and release plumes of degenerate matter, which fissions down to the elements we know.
Science News Thread (for articles that don't relate to ongoing discussions)
in Science & Spaceflight
Posted
https://news.cornell.edu/stories/2022/02/new-catalysts-steer-hydrogen-fuel-cells-mainstream
Cheaper fuel cells, yay!