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Comment by mmooss | Hacker News Reader

NASA's next space station will be in lunar orbit:

https://www.nasa.gov/mission/gateway/

This isn’t a normal useful orbit in terms of supporting astronauts on the moon or being available for recovery etc. and was definitely not used to support earlier moon landings. I think it only has a lunar revisit once every 7 days. Imagine your abort / recovery to orbit option is only available for this one tiny window.

SLS probably can’t get Orion to Lunar orbit unfortunately so they have created this insanely costly / complex / lower utility approach.

About orbits: https://news.ycombinator.com/item?id=42538057

It's surprising to see that every comment's angle is spreading Musk's stories, trashing his competition, etc.

It's worth mentioning that Gateway is on the cutting block if the likely SLS cancellation happens during this incoming administration. As the entire reason for Gateway existing and being where it is is to act as a destination for SLS before the moon landing program was announced. It is where it is because of the relatively weak performance specifications of the SLS rocket preventing it from launching the Orion spacecraft into a low lunar orbit. SLS was also destined to launch several of the Gateway modules which would be impossible if its canceled.

Yes I could see deals being worked out where gateway partners instead build parts of a lunar base. The international partnerships a likely the biggest piece going for gateway in terms of not being cancelled

It seems to me that if SLS goes… so does Gateway. That said, one thing to note: There are not that many stable lunar orbits. Unlike the earth, the moon is very lumpy. It is the reason why most lunar orbiters end up doing a planned crash as their end of (relatively) short life. From that standpoint, orbits that are a bit further out are much more appealing to have relatively low delta v requirements.

All that said, once Starship is regularly in use for lunar delivery… I suspect we will have a fundamental new paradigm for space.

There are low lunar orbit frozen orbits that don't do that.

> As the entire reason for Gateway existing and being where it is is to act as a destination for SLS

I don't think that's true. I've long heard of it as support for surface operations and for preparation (R&D, etc.) for Mars.

"A space station" is desireable. The lunar gateway, though, as designed, is very much about Artemis. The Near Rectilinear Halo Orbit[1] was designated because of constraints on the Orion capsule that will be attached during crewed operations, at least this was relayed to me directly by NASA personnel during a Q&A.

[1] - https://en.wikipedia.org/wiki/Near-rectilinear_halo_orbit

It has more to do with reducing propellant needed for station keeping. NRHO is useful for lunar fuel depots.

One of the goals of gateway is to act as a test bed for long term manned operations outside of low earth orbit. I.e. start developing and proving the technology in flight that we are going to need for a mars mission.

The conops for this doesn’t make sense to me. Not only is it in a weird orbit but after the first lunar landing, which will have two astronauts, the rest will have four. With all 4 crew members on the lunar surface who will be working on gateway? SLS can max launch once a year. Are we really going to give up a lunar landing opportunity for a gateway only mission? Already 1 mission a year for a couple weeks is a big change from a quarter century of continuous operations on ISS. Mix of commercial space stations in LEO supported by regular NASA crews and lunar mission with eventual base seems the most inspiring and beneficial way to keep consistent presence in space was explaining exploration and building private space capability/infrastructure.

It might be interesting to look up Gateway's mission and see why they are putting it in in orbit around the Moon rather than Earth. I know a major part of it is to learn the lessons needed for a human trip to Mars.

> Not only is it in a weird orbit

Regarding lunar orbits (I don't know about Gateway's orbit):

We are used to relatively stable gravity in Earth orbit, but it is much different out near the Moon: Gravity in cislunar space creates chaotic trajectories due to the three-body problem of Earth, Moon, and the vehicle. Orbits around the Moon are also much less stable than around Earth. There are only a few stable orbits, all below 700 km.

Here's a pretty good resource:

https://www.afrl.af.mil/Portals/90/Documents/RV/A%20Primer%2...

I assume SLS’s shelf life is limited and we’ll be using Starship end to end within 5 years or so.

  >With all 4 crew members on the lunar surface who will be working on gateway?

One of the technology advancements being pushed by Gateway is that (unlike ISS) it wouldn't require a constant human presence.

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