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Good. The lunar gateway has absolutely no purpose now that that asteroid retrieval mission (ARM) funding picks by NASA ignored all the de-spin proposals. Withou

Good. The lunar gateway has absolutely no purpose now that that asteroid retrieval mission (ARM) funding picks by NASA ignored all the de-spin proposals. Without the ability to de-spin the number of accessible near earth asteroids (NEA) to tow back to the lunar gateway numbers, literally, 3. It would be a huge waste of time and money to implement a lunar gateway that doesn't have the ability to gather resources. Going to the moon's surface and back for fuel resources is currently infeasible due to the large delta-V required and lack of atmosphere to aerobrake against.

Sir_Cmpwn 7y ago
It only takes 1.87 km/s to get from the moon's surface to LLO, and there's fuel and science and real estate at the bottom. The delta-V budget of, say, LLO to the nearest Earth-Moon Lagrangian point is about 1 km/s. So yeah, it's more expensive to go to the lunar surface, but it's not outrageous and there might be other benefits to round-trips to the surface.
- avmich 7y ago
  In addition to orbital velocity (~1.7 km/s) and gravity losses (~0.2 km/s?) you should take into account all safety reserves - Eagle could hang a minute or more above the surface selecting the place to land. Given that we can't ignore safety, it's better to budget 2200-2500 m/s delta-V to get from the Moon orbit to the Moon surface. We need both Lagrange point stations and surface bases. It's arguable what should go first; an argument for Lagrange station is that it's easier to build.
  - manicdee 7y ago
    By the time we are collecting fuel from the lunar surface there will be well marked solid landing pads and no need for thirty seconds of reserve fuel to scoot over to a new landing site.
rbanffy 7y ago
Even Orion is a bit cramped for a multi-week excursion. Having the extra living space and long-duration equipment in-place and only taking expendable supplies there is a good way to save mass. I am skeptical of the utility of in-space refueling when you need to ship fuel from Earth, but not having to ship the lander and ascent vehicle for every roundtrip sure is nice.

Sir_Cmpwn 7y ago

It only takes 1.87 km/s to get from the moon's surface to LLO, and there's fuel and science and real estate at the bottom. The delta-V budget of, say, LLO to the nearest Earth-Moon Lagrangian point is about 1 km/s. So yeah, it's more expensive to go to the lunar surface, but it's not outrageous and there might be other benefits to round-trips to the surface.

avmich 7y ago
In addition to orbital velocity (~1.7 km/s) and gravity losses (~0.2 km/s?) you should take into account all safety reserves - Eagle could hang a minute or more above the surface selecting the place to land. Given that we can't ignore safety, it's better to budget 2200-2500 m/s delta-V to get from the Moon orbit to the Moon surface. We need both Lagrange point stations and surface bases. It's arguable what should go first; an argument for Lagrange station is that it's easier to build.
- manicdee 7y ago
  By the time we are collecting fuel from the lunar surface there will be well marked solid landing pads and no need for thirty seconds of reserve fuel to scoot over to a new landing site.

rbanffy 7y ago

Even Orion is a bit cramped for a multi-week excursion. Having the extra living space and long-duration equipment in-place and only taking expendable supplies there is a good way to save mass. I am skeptical of the utility of in-space refueling when you need to ship fuel from Earth, but not having to ship the lander and ascent vehicle for every roundtrip sure is nice.