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It seems that lunar darkside observatory can't come soon enough: it would be immune to much of this suspected human interference. It would also be relatively ea

It seems that lunar darkside observatory can't come soon enough: it would be immune to much of this suspected human interference. It would also be relatively easy to set up with existing robotic rover tech, laying long runs of wire on the surface.

Already__Taken 6y ago
would it even be useful just to put and antenna pointing at earth from the moon just to transmit "this is the noise floor of yourself" later add a dark side listener to difference the signals?
giantrobot 6y ago
Lunar observatories are awesome in theory but very face a lot of issues in practice. The first is just lifting their mass. The 64m dish at Parkes observatory weighs in at about 1000 tons [0]. An expendable Falcon Heavy can lift about 26t to GTO which is a bit more than it could put into a TLI. Let's say 22t into TLI. That vehicle needs to actually land on the Moon rather than orbit or crash into it so usable payload to the Lunar surface will be much less than the vehicle/fuel mass. Let's say 14t since it's all unpressurized payload. That's for $150m a pop. You'll need at least 71 of those launches which comes out to a cool $10.6b. The construct-o-bots will need a few more launches so let's round up to $11b. That's all assuming building a huge instrument on the far side of the Moon with robots is all a solved engineering problem. Then there's the Lunar environment. The reason the Moon is covered in Moon dust is because it is constantly bombarded with micrometeoroids. I'm pretty sure the operating manuals for a lot of the sensitive instruments mounted on the Parkes dish say "don't shoot with a gun" which is about the energy equivalent of a lot of micrometeoroids IIRC. One hit to a cryogenically cooled receiver will result in it ceasing to be cryogenically cooled. That tens of billions of dollars for one Parkes equivalent could buy you about 60 FASTs (~$170m) or 30 Arecibos (~$350m).
- imglorp 6y ago
  I was not proposing carrying a dish, instead lay long runs of wires on the surface in whatever pattern you like. But if you want a parabaloid, chose a darkside crater and do the Arecebo thing there. Also, some frequencies are not possible on Earth at all due to ionosphere attenuation.
  - giantrobot 6y ago
    Sorry I was under the impression you were talking about a radio telescope and not just a big shitty antenna. /s Wire antennas for a radio telescope are not a great solution. A giant array of antennas (still a lot of mass to lift) could have decent angular resolution but not great seeing power. The seeing power of a telescope is a function of the totally collector surface area. A big dish literally reflects photons that hit any part of the surface. A wire antenna with no reflector has a teeny tiny surface area. For an antenna array you'd still need steering sturdy mounts, steering systems, and power for those steering systems. Just using big wires means you can't really steer the focus and has far less gain than an array and way less than a system using reflectors. TANSTAAFL.
- lucb1e 6y ago
  > The 64m dish at Parkes observatory weighs in at about 1000 tons But GP wasn't talking about any dish. Just wires.
- m4rtink 6y ago
  Lunar Starship (if built) could put tens of tons of equipment on the Lunar surface in a fully reusable manner (provided all works out as intended), so even your example might actually be duable. Most likely a more mundane setup might be a better first project + due to 1/6 g and no storms to withstand the antennas could likely be much lighter.
  - giantrobot 6y ago
    Starship isn't a very good option. While Starship can lift a lot of mass to LEO in order for it to be reusable it needs to then get it all to the Moon's surface and then take off from the Moon's surface and then get back to Earth. Every gram of fuel is one less gram of payload. So a Starship either needs to carry all of its fuel needed for Lunar take-off and TEI (significantly reducing payload) or refuel on site. Since there's no LOX and Methane deposits on the Moon every Starship Moon landing would need both sent to the Moon ahead of it. Even if you want to assume you can find a bunch of water ice under the regolith you then need to send up a water cracking factory, compressors, and literally tons of solar panels. Then you still don't have any methane. So even if you just have to send methane you've had to build a huge amount of infrastructure out of technology that doesn't exist just to reuse Starships. If you don't reuse Starships you don't get much dollar savings over using Falcons. Starship is designed to use aerobreaking for landing. This is something that's viable on Earth and Mars but useless on the Moon. So any Starship landing on the Moon needs fuel to de-orbit and land, with aerobreaking only the terminal phase of the landing needs fuel. Starship's economics only really work if there's fuel available in LEO, its destination, and its destination has an atmosphere for aerobraking. If those things aren't true it needs to carry all of the fuel needed for its mission from Earth's surface which significantly reduces its payload. Doing shit in space is hard.
    - techdragon 6y ago
      Lunar Starship would involve on orbit refuelling and cargo transfer if used as a reusable lunar lander. In case your unfamiliar there’s a specific variant of Starship being proposed (and built?) for landing on the lunar surface it’s designed to avoid problems like having those big raptor engines blast tons of lunar dust around. So using starship to loft the payload into orbit on a reusable launcher, and lunar starship to land it re-usably on the moon is probably one of the only near term practical methods to large scale lunar construction, everyone else keeps throwing away expensive hardware.
- _ph_ 6y ago
  Any structure designed for setting up on the moon could be much lighter than its earth counterpart. It only needs to withstand 1/6th of the gravity and doesn't have to withstand storms. Even if they wanted to replicate the Parkes telescope, it would require much less material.
  - akiselev 6y ago
    Without an atmosphere to burn them up, even the tiniest microasteroids can cause catastrophic damage due to their velocity and these events are very common on the surface of the moon. It might need less material support the weight but a hell of a lot more material to shield any mirrors/dishes and electronics from certain damage.
m4rtink 6y ago
There are even some preliminary designs based on existing lunar lander & rover tech - no (manual) assembly required! https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_I_Phase_II/lunar_crater_radio_telescope/ https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...
baja_blast 6y ago
It would probably be easier to fly two mechanics up in SpaceX's Starship and just install it. No rovers needed!

Already__Taken 6y ago

would it even be useful just to put and antenna pointing at earth from the moon just to transmit "this is the noise floor of yourself" later add a dark side listener to difference the signals?

giantrobot 6y ago

Lunar observatories are awesome in theory but very face a lot of issues in practice. The first is just lifting their mass. The 64m dish at Parkes observatory weighs in at about 1000 tons [0]. An expendable Falcon Heavy can lift about 26t to GTO which is a bit more than it could put into a TLI. Let's say 22t into TLI. That vehicle needs to actually land on the Moon rather than orbit or crash into it so usable payload to the Lunar surface will be much less than the vehicle/fuel mass. Let's say 14t since it's all unpressurized payload. That's for $150m a pop. You'll need at least 71 of those launches which comes out to a cool $10.6b. The construct-o-bots will need a few more launches so let's round up to $11b. That's all assuming building a huge instrument on the far side of the Moon with robots is all a solved engineering problem. Then there's the Lunar environment. The reason the Moon is covered in Moon dust is because it is constantly bombarded with micrometeoroids. I'm pretty sure the operating manuals for a lot of the sensitive instruments mounted on the Parkes dish say "don't shoot with a gun" which is about the energy equivalent of a lot of micrometeoroids IIRC. One hit to a cryogenically cooled receiver will result in it ceasing to be cryogenically cooled. That tens of billions of dollars for one Parkes equivalent could buy you about 60 FASTs (~$170m) or 30 Arecibos (~$350m).

imglorp 6y ago
I was not proposing carrying a dish, instead lay long runs of wires on the surface in whatever pattern you like. But if you want a parabaloid, chose a darkside crater and do the Arecebo thing there. Also, some frequencies are not possible on Earth at all due to ionosphere attenuation.
- giantrobot 6y ago
  Sorry I was under the impression you were talking about a radio telescope and not just a big shitty antenna. /s Wire antennas for a radio telescope are not a great solution. A giant array of antennas (still a lot of mass to lift) could have decent angular resolution but not great seeing power. The seeing power of a telescope is a function of the totally collector surface area. A big dish literally reflects photons that hit any part of the surface. A wire antenna with no reflector has a teeny tiny surface area. For an antenna array you'd still need steering sturdy mounts, steering systems, and power for those steering systems. Just using big wires means you can't really steer the focus and has far less gain than an array and way less than a system using reflectors. TANSTAAFL.
lucb1e 6y ago
> The 64m dish at Parkes observatory weighs in at about 1000 tons But GP wasn't talking about any dish. Just wires.
m4rtink 6y ago
Lunar Starship (if built) could put tens of tons of equipment on the Lunar surface in a fully reusable manner (provided all works out as intended), so even your example might actually be duable. Most likely a more mundane setup might be a better first project + due to 1/6 g and no storms to withstand the antennas could likely be much lighter.
- giantrobot 6y ago
  Starship isn't a very good option. While Starship can lift a lot of mass to LEO in order for it to be reusable it needs to then get it all to the Moon's surface and then take off from the Moon's surface and then get back to Earth. Every gram of fuel is one less gram of payload. So a Starship either needs to carry all of its fuel needed for Lunar take-off and TEI (significantly reducing payload) or refuel on site. Since there's no LOX and Methane deposits on the Moon every Starship Moon landing would need both sent to the Moon ahead of it. Even if you want to assume you can find a bunch of water ice under the regolith you then need to send up a water cracking factory, compressors, and literally tons of solar panels. Then you still don't have any methane. So even if you just have to send methane you've had to build a huge amount of infrastructure out of technology that doesn't exist just to reuse Starships. If you don't reuse Starships you don't get much dollar savings over using Falcons. Starship is designed to use aerobreaking for landing. This is something that's viable on Earth and Mars but useless on the Moon. So any Starship landing on the Moon needs fuel to de-orbit and land, with aerobreaking only the terminal phase of the landing needs fuel. Starship's economics only really work if there's fuel available in LEO, its destination, and its destination has an atmosphere for aerobraking. If those things aren't true it needs to carry all of the fuel needed for its mission from Earth's surface which significantly reduces its payload. Doing shit in space is hard.
  - techdragon 6y ago
    Lunar Starship would involve on orbit refuelling and cargo transfer if used as a reusable lunar lander. In case your unfamiliar there’s a specific variant of Starship being proposed (and built?) for landing on the lunar surface it’s designed to avoid problems like having those big raptor engines blast tons of lunar dust around. So using starship to loft the payload into orbit on a reusable launcher, and lunar starship to land it re-usably on the moon is probably one of the only near term practical methods to large scale lunar construction, everyone else keeps throwing away expensive hardware.
_ph_ 6y ago
Any structure designed for setting up on the moon could be much lighter than its earth counterpart. It only needs to withstand 1/6th of the gravity and doesn't have to withstand storms. Even if they wanted to replicate the Parkes telescope, it would require much less material.
- akiselev 6y ago
  Without an atmosphere to burn them up, even the tiniest microasteroids can cause catastrophic damage due to their velocity and these events are very common on the surface of the moon. It might need less material support the weight but a hell of a lot more material to shield any mirrors/dishes and electronics from certain damage.

m4rtink 6y ago

There are even some preliminary designs based on existing lunar lander & rover tech - no (manual) assembly required! https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_I_Phase_II/lunar_crater_radio_telescope/ https://www.nasa.gov/directorates/spacetech/niac/2020_Phase_...

baja_blast 6y ago

It would probably be easier to fly two mechanics up in SpaceX's Starship and just install it. No rovers needed!