shynung

Not sure about that. I might have to dig around when I have the time. You're still spraying nuclear reaction products everywhere. That's the problem with open cycles.

It's just as clean as any open-cycle nuclear rocket, which is to say not very clean at all. OP wasn't looking for ecologically-clean rockets, but politically-clean ones. Out there, we don't really care what comes out of the nozzle, since the exhaust will be far too spread out to do much damage to practically anything. Unless it's a mass driver, that is. You were probably thinking of the Hafnium fiasco.

Okay, yeah, it's not actually a freezer ship. More like refrigerator ship. Also, the medical personnel was supposed to stay on Earth, giving instructions to the robot arm operator (or Be the robot arm operator) that takes care of the sleeping payload. I have concerns about reaction time, though, due to the lightspeed lag.

2 years ago, SpaceWorks compiled a report covering a possible method of transporting astronauts to Mars. https://www.nasa.gov/sites/default/files/files/Bradford_2013_PhI_Torpor.pdf Short version, SpaceWorks is working on a method to induce hibernation-esque effect on astronauts via induced therapeutic hypothermia, which cools the body by about 15 degrees C. The report says that by using this approach, we can cut down on transfer vehicle habitat mass by about 52% compared to NASA's own Mars DRA 5, at the expense of putting IV plugs in everyone onboard. What are your opinions?

For nearby destinations like Venus, the Moon, Mars, and maybe NEOs, current chemical rockets would do perfectly fine. Ion thrusters could work, but it would take quite some time. Not ideal for time-limited missions, but feasible nevertheless. Mercury, that's another matter.

Maybe you should bug him about it. I'd love to have it in the next release.

The problem with this approach is that nuclear energy is the only source of power that can be used almost anywhere. Chemicals don't have good energy density, and solar panels are nearly useless past Mars. Unless you're happy with confining your spaceborne adventures to the inner solar system, you will have to transition to nuclear power eventually. That is, unless you are willing to deal with the horrors of high-energy chemical reactions. LH2/LF2 engines have a better performance than LH2/LOX, but the dangers of liquid fluorine makes nuclear rockets seems safe in comparison.

Better chemical rockets. The kind dreamed by actual propellant alchemists like John D. Clark, author of Ignition. He wrote of tripropellant rocket motors that gave 542 seconds of ISP , and burned cooler than LH2/LOX. Said rocket runs on LH2, liquid Fluorine, and liquid Lithium, substances that are not only expensive, highly toxic and corrosive, but also has wildly different storage temperature requirements. So that's that. And then there are ideas like this. In short, burning dimethylmercury (a corrosive neurotoxin that goes through latex gloves like it's not even there) with dioxygen difluoride (a highly sensitive oxidizer that likes to explode at will, burns anything it touches, and is generally unpleasant). And to top it all off, the mercury is a metastable (half-life of 30 minutes) isomer that has been irradiated in a nuclear reactor for months, ready to let all that stored energy out at once with a little boost of X-rays. No, I'm not saying we should use these things.

Physical size depends on what it's supposed to carry. If it's just a bunch of sensors and computers, a ship that fits into a 3x3x3 m box will do the job (New Horizons).

Not portable heating devices, mind you. Household appliances. Think stoves and ovens. Stuff like camp stoves would still use fuels. It doesn't have to happen overnight. Cars are built to last decades. It's completely fine to wait until the current generation's cars to be used until they break down or scrapped (or the owners get sick of high fuel prices), while slowly being replaced by newer generation electrics. The infrastructure upgrades should follow as the automobile fleet upgrades. Use the light hydrocarbons for long distance. I'd say something like Chevy Volt's energy usage plan (use battery until it's low, then turn on engine/generator) should be enough. Also, while large commercial aircraft's pretty much stuck with hydrocarbon, electric rockets already exist: ion thrusters, arcjets, resistojets, magnetoplasma thrusters (VASIMR), and more.

The bolded part is the scenario I'm talking about. There should be a time where everyone ditches almost every fuel-burning appliance (think gas stoves) and personal vehicles, because electricity would be much cheaper than the alternative energy sources. So what? In an urban environment, almost every inhabited building is connected to the grid anyway. Installing charging spots for cars wouldn't be very difficult. It's just a matter of time until everyone living in cities commute using electric vehicles. In long distance routes where putting charging stations every few kilometers aren't an option, use vehicles fueled by light hydrocarbons, like methane or ethanol. These are easier to synthesize than octane (main component of gasoline), because the carbon chain is shorter. In case people insists on using their electric daily driver, just have them rent a small generator trailer which charges their battery on the go. Even then, battery technology is still advancing. A low-end brand new electric vehicle can go about 160 km in one charge (Nissan Leaf), while a more high-end model reaches 430 km (Tesla Model S).

I agree. The cars themselves may be automated to the point of becoming the horizontal equivalent of personal elevators, but people have been accustomed to having them nearby, ready to take them anywhere, I don't think we'll ditch personal cars anytime soon. However, there are some places where human driving might come in handy (out in the wilderness, for example), and some people enjoys driving, so I don't think human driving would completely vanish. It'll be much highly regulated, probably similar to today's pilot licenses.

When fusion power (or any advanced nuclear power) goes online on a large scale, electricity would become dirt cheap compared to today. Cost per kilometer traveled on electric vehicles would've dropped so much, everyone would jump to electric cars in hordes. Car manufacturers would then follow their whims, and produce better electric cars.

An RL-10 with 4000 seconds ISP. The actual RL-10's ISP is about 1/10 of that.

Sounds like something the late John D. Clark would attempt doing.

And that solar panel costs more than a patch of land. And the factories producing the panels needs to be fed power as well. Even if we use clean energy sources, an air liquefier/separator facility takes a lot of resources just to set up. Setting up a farm involves marking/fencing off a patch of land and building garages/warehouses for tractors/farm machinery. Also, farming in deserts are not impossible. The key is efficient irrigation and soil management, along with pest control. Yes, I get your point. Plants aren't the most efficient method of carbon extraction. It is, however, much more affordable logistically. Sure, in a heavily-industrialized locale where space is scarce and crude oil is fantastically expensive, atmospheric carbon extraction plants may make more sense than an energy-oriented farm. But we haven't reached that point yet, as far as I know.

Sure, but plants are self-powered. An atmospheric CO2 harvesting plant needs to filter 2.5 tons of air for every kilogram of CO2 they take. All these processes requires power from somewhere, either the electrical grid or onsite generators. With crops, all they need is plenty of water and sunlight, which can be supplied with far less effort than electricity, in terms of infrastructure and energy requirements.

Yes, it is. Several month's worth of absorbed atmospheric CO2, ready for the taking. Though, the same is true of oil and coal. Main difference is that the carbon from oil and coal was absorbed millions of years ago, and got buried. What we hauled out was atmospheric CO2 from the ancient ages.

@p1t1o is right. CO2 concentration in the atmosphere is minuscule compared to oxygen, or even argon. Our best bet for carbon sources, other than oil, are coal (AKA solid chunks of carbon), followed by various biological sources such as wood, sugary crops, and recently cellulosic plant parts.

I don't understand how much that panel it would produce under what conditions given this bit of information, unfortunately. I'd need power density (in kW/m2). Or, just point me to the specs of a currently-available solar panel. Given power and mass density, I can calculate total panel area and mass.

We can burn ethanol and syngas biofuels in modern engines today, just need adjustment in compression ratios and boost pressures and the like. Or, if we're talking gas turbines or steam engines, almost no modification other than fuel delivery system. Also, synth-oil would probably be more expensive than natural crude oil, because natural oil already has long carbon chains straight out of the well. Synth-oil technologies mainly deals with combining carbons from other sources (sugar, atmospheric CO2, methane) into chains long enough to do the job of natural-oil products. Right from the start, synth-oil production is already more energy intensive by mass compared to natural-oil production, so it will only be cheaper if natural-oil gets very rare.

Better yet, those wood gas generators work on any carbon-based solid fuels. Coal, coconut shells, most should work.

Problems with both approaches are the energy crops competing for arable land against the food crops. Also, the machines that do the farming (tractors) drink gobs of fuel. IMO, we should be looking for ways that turn agricultural byproducts into fuel. Cellulose, found in plants (or parts of it) that are inedible to humans, can be turned to ethanol by first breaking it down into simple sugars (glucose) by using enzymes similar to those found in ruminants.

What about lubricants? Motor oil and the likes?

That's an exhaust velocity of around 39 km/sec. 100 kN would mean a mass flow of a touch above 2.5 kg/sec. Accelerating that propellant would need just over 1.9 MW, plus energy needed to ionize 2.5 kg/sec of propellant.