Space Infrastructure

Draft

Most spacecraft are built, flown and discarded. This section covers the exceptions: systems intended to persist, be maintained, be extended, or manufacture something.

Reading order

The three habitation pages share a common problem set. The last four are independent propositions, each with its own economic case.

The numbers that bound this section

Radiator area

A = \frac{Q}{\varepsilon\sigma T^4}

About 2.6 m² per kilowatt at room temperature. This is the constraint that bounds orbital computation, and it is set by the Stefan-Boltzmann law rather than by any technology.

Beam spread from geostationary orbit

D_{\text{rx}} \approx \frac{\lambda}{D_{\text{tx}}} \times 35\,786\ \text{km}

At 2.45 GHz, a one-kilometre transmitter needs a five to ten kilometre rectenna. Diffraction is why space-based solar power is a kilometre-scale proposition and also why the beam cannot be concentrated into a weapon.

Four things worth knowing

Space is an excellent insulator, not a cooling system. The frequently repeated claim that orbit offers free cooling is backwards. With no convection and no conduction, radiation is the only path out, and it needs area comparable to the solar array that generated the power.

The 14-day lunar night is what forces fission power. Storing two weeks of energy in batteries does not close at any useful scale, so a base away from the few near-continuously lit polar rims needs a reactor.

Mars surface radiation is lower than transit radiation. Curiosity measured 0.64 mSv per day on the surface against 1.8 in cruise. The dangerous part of a Mars mission is getting there, which makes it a propulsion problem.

Refuelling breaks the rocket equation into pieces. A mission fuelled in orbit pays the exponential penalty on each leg separately rather than on the sum, which is the difference between a lunar architecture that fits on one launch and one that does not.

Pages

01Space stations

What permanence requires that a spacecraft does not, the ISS as an engineering and political artefact, logistics and the lifeboat constraint, what microgravity research has produced, and the commercial successors.

02Lunar surface systems

Polar site selection, surviving the 14-day night and why that means fission power, regolith shielding and lava tubes, dust as the dominant operational problem, and construction from local material.

03Mars habitats

Living with a 26-month resupply interval and no abort, radiation on the surface against in transit, power and dust storms, water as the site selection driver, and the unknown effects of 0.38 g.

04In-space manufacturing and assembly

How the fairing constrains what can be designed, robotic servicing and what Hubble and MEV demonstrated, printing spares against printing structures, and products that need microgravity.

05Refueling and propellant depots

Why single-launch architecture is expensive, depot locations and architectures, cryogenic boil-off, transfer when there is no bottom to the tank, and what depots unlock.

06Space-based solar power

The energy argument and its real magnitude, microwave against laser transmission, rectenna sizing and why the beam is not a weapon, and the economics against a terrestrial competitor that is also getting cheaper.

07Orbital data centers and edge compute

Why downlink scarcity is the real argument, the thermal rejection limit that binds harder than power, commercial silicon with fleet-level fault tolerance, and which claims survive examination.