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A hovercraft might be able to do it. An Addis Single Rail Tramway, too. I expect ground conditions preclude traditional dual rail, but perhaps an Addis Tramway could do it, since there's no need to align rails. Just one rail to bear the weight and something vaguely road like for the balancing wheels. Might need quite narrow and long trains to keep the ground pressure low idk.

I recall talking about ceiling mounted radiators? Easier to retrofit and don't get covered up by furniture.

Once you reach maybe 20-30mb, you can have water covering your habitat to provide the counterpressure. Hellas Basin is 7km down and has double surface pressure, so maybe 14km would do the trick to get stable ish surface water?

The viability of launch assist for SSTO would seem to depend a lot on whether its for humans or for dumb cargo. Containers of plastic or water or metal can take the high accelerations needed. Squishy humans cannot.

Fortunately, most of the stuff we need to get up there is stuff that can take the high accelerations, especially if we can turn it into what we need once its on orbit.

I had that idea also, but thats not what I'm suggesting here. This is about using an electromagnet to pick up an object and swing it around. It's a centrifugal accelerator using a magnetic transmission.

A rotating drum could be used for coilgun switching. Put magnets along its length in a spiral pattern, as it turns the magnets pass and activate the switches. Or even a single flywheel, the spacing is what matters e.g. at a constant RPM, if magnets are placed at 0, 180, 270, 315 deg. the time between each switching will be half the previous one. For a coilgun you could also energise all coils at the start and use the switches to turn them off?

Coming back to Earth, I'm wondering what sort of performance compressed air/propane rockets could get. Not for sustaining flight, but for providing the high thrust needed for launch, particularly for a microlight/glider. It would only be used for a few seconds, so the tank can be refilled on the ground using solar power or other sources. The compressor would only operate one way, since the air is leaving via the combustion chamber; idk if that makes it easier and lighter to build. The weight of the tanks may make it tricky to use for for VTOL, though carbon fibre might be light enough. Could allow STOL though if retrorockets are included.

For Martian transport,  Lithium Hydride Thermal Rocket. Robert Zubrin proposed an NTR that would use CO2 propellant,  the Nuclear Indigenous Martian Fuel (NIMF). That would have been designed to reach orbit. This would not, but it should be capable of at least short range ballistic hopping. Molten LiH has a heat of fusion of 2.9 MJ/kg at 690c; if the Isp was 145, that would mean 4 kN-s of thrust per kg, so a craft that has 10% of its mass dedicated to a thermal battery would have enough energy for a delta V of 400m/s. Enough for a few km of high speed hopping. 20% battery would be able to hop 10km with some napkin math. Or more likely, enough to get a fixed wing aircraft airborne and up to cruising speed?

TH,

Its not an issue of understanding. I understand GW perfectly well, I just reject his vibes based design in favour of solid evidence that it's massively overkill.

https://satsearch.co/products/pale-blue … t-thruster

Assuming the energy cost per N-s for a lithium hydride thermal rocket is 2kJ, we would need 440kJ to match this for total impulse. That would be about 150g of LiH, with double the Isp. But of course, we wouldn't be using anywhere near that much, since the point is to regenerate with solar power. Such a storage system would be useful for raising orbits through perigee kicks, not something feasible with solar electric systems.

I have thought for a while about stratospheric light gas gun launch. Reading the spin launch thread, it appears that 10,000g is doable. To get to 8km/s at that acceleration, the barrel needs to be just over 300m long. For a stratospheric airship that is not a great length. The advantage over a ground based system is the far reduced air density to get through, as well as the ability to move where the accelerator is pointing to access different orbits.

It may also be possible that an airship could reach 2km/s under its own propulsion. Maybe solar thermal, even. If it could do this repeatedly without much issue, that would be a very good first stage.

I already linked the study in the original thread. They had people use them for 25 minutes at a time, each day for 50 days. I'm going off data here, not vibes.

https://pmc.ncbi.nlm.nih.gov/articles/PMC7450067/

The reason fairground rides don't last longer than a couple of minutes is that they need a high throughput of people to make money, not because they're hitting some fundamental limit of biology.

GW,

As I have repeatedly pointed out, we don't have that data, and the 3-5RPM limit is entirely vibes based, typically from people who don't know what they're talking about. But we *know* people can tolerate 10RPM for at least half an hour. And getting longer term data is well within our means.

Incidentally, the existence of playground roundabouts does tell us one important thing, which is that children at least aren't badly affected by spending half an hour to an hour each day rotating at 20RPM.

2m radius, 6RPM, force of 0.08g on the outside. Need to angle the floor a bit. But it should be enough space for someone to spend a few days inside. A larger one for weeks to months would be maybe 10m radius with signficantly more angled flooring. But again, it's not exactly a pricey experiment to run.

EDIT: just turned slowly in a circle whilst timing myself. 7RPM. It's tolerable enough.

Also, transient high rotation is enough for excercise. We can use a lower gravity for day to day activities, only the gym needs to be spun up to full g. And we actually do have data that says high rotation is not a problem for such stretches of time.

RTGs using more efficient energy conversion and suitably containable isotopes might achieve power densities comparable to nuclear reactors for certain applications. Strontium titanate puts out about 250W/kg; it doesn't seem unlikely to me that a 1 tonne complete system could achieve 100kWe.

If we get good at nuclear tramsmutation, perhaps we can achieve far higher power densities than that. Even if it's very poorly performing as an energy storage system, the energy to produce it would come cheaply from large solar farms, and provide something far more suitable for use in spaceships.

Keen on antimatter mining too of course. Maybe we'll finally get fusion power... Once we reach Jupiter and can harvest plentiful antimatter to use as the trigger.