Astronomers want to plant telescopes on the Moon.

[YNM]

1 hour ago, JoeSchmuckatelli said:

but to build a crater antenna on the Moon?  

 

You would need a fleet of big ships. 

The dish would be made out of wire mesh, which you can fold down into smaller area. So dimensions aren't a problem.

You're kind of right on the amount of material it might need, though. Arecibo have about 85,000 m² of dish area, while FAST have about 196,000 m². I'm honestly not sure how thick do we need the wires be for it to be viable, but assuming a wire mesh with pitch size (size of the 'holes' / spacing of the wires) of 6.35 mm x 6.35 mm (1/4" x 1/4") the quoted weight from a fence manufacturer using 0.46 mm diameter galvanized steel wire is 4 kg for 9 m² of mesh (about 445 g/m²), which works out to 88 tonnes (FAST sized) or 38 tonnes (Arecibo sized) dish. The heaviest mesh I see from this manufacturer is for 5 cm x 5 cm pitch using 4 mm dia. steel wire which makes for ~4 kg/m2 (so 10 times as heavy). We haven't talked about the support structure for the receiver, the jacking for the dish, the observation equipment and data handling (copper cables as well) etc.

But it's still less than for a mobile 7 m or 12 m dish antenna array numbering up to a hundred I guess. Not sure how heavy those would end up being as well however...

Then again because it's simpler perhaps producing the wire mesh itself could be the subject of space mining/extraction and manufacturing technology testing, given aluminum is aplenty over there. Making wire mesh is kind of easy as well (just straight extrusion then spacing and ERW).

Edited February 20, 2021 by YNM

[kerbiloid]

Did somebody hear about?

https://en.wikipedia.org/wiki/EASE/ACCESS

Spoiler

 

Edited February 20, 2021 by kerbiloid

[YNM]

13 minutes ago, kerbiloid said:

Did somebody hear about?

Lunar surface isn't exactly 0g / free-fall. Plus those are trusses, which goes into rigid structures. Dishes that doesn't need to move can be closer to non-rigid catenary system.

[tater]

The stuff you want in space is IR to submm radio, and long wave (>~11m wavelength).

Radio is easier in many ways for the Moon as you need not worry about harming the equipment as much with dust from landers. Long wave is not going to be dishes anyway, they'd need to be huge.

Steerable radio telescope design is pretty complex as the accuracy of the reflector needs to be surprisingly high. When you start pointing it, you need to consider that the forces slightly bending it are very different when pointing at some arbitrary elevation vs when it is "champagne glass" and pointed straight up. Thermal loading will also deform it (that's gotta be really extreme on the Moon).

Obviously building to Earth specs will do well on the gravitational loading side, but the mass penalties are huge.

 

Carbon fiber does well for the thermal limits, and better for gravity limits (sagging deformation). Of course the above is for 1g. For submm, thermal constraints will dominate. Luckily those telescopes can be small.