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posted by martyb on Friday December 28 2018, @06:43AM   Printer-friendly
from the ask-Senator-Shelby dept.

Submitted via IRC for takyon

An article at SpaceNews.com asks Is the Gateway the right way to the moon? — the "Gateway" is The Lunar Orbital Platform-Gateway.

This article originally appeared in the Dec. 17, 2018 issue of SpaceNews magazine.

Sometime in 2028, competing for attention alongside a presidential election and the return of the Summer Olympics to Los Angeles, NASA will return humans to the surface of the moon.

A lunar lander will depart the cluster of modules in an elliptical orbit around the moon, called Gateway, and descend. One stage will take the lander to a low lunar orbit and then separate, after which the descent module will handle the rest of the journey to the lunar surface. A crew of up to four will spend days — perhaps up to two weeks — on the surface before boarding the ascent module, which will take them back to the Gateway.

At least that’s NASA’s plan for now. A year after President Donald Trump formally directed NASA to return humans to the moon in Space Policy Directive (SPD) 1, the agency has developed the outlines of a plan to carry that out, while emphasizing the language in the policy to do so in a “sustainable” manner and with international and commercial partners. But as the agency describes two of the biggest elements of the plan, the Gateway and a “human-class” lunar lander, it’s still struggling to sell the proposal to its various stakeholders, including its own advisers.

[The somewhat long article is well worth a read. Notable members of NASA as well as former astronauts weigh in on their views of the pros and cons of such an approach as opposed to direct flights to and from the moon. To my eye, NASA was instructed to make the Deep Space Gateway happen so there was a destination for the Space Launch System (SLS) which currently costs something like $2 billion per year in launch and development costs. By comparison, I recall reading that SpaceX anticipates it can develop its next-generation Big 'Falcon' Rocket (BFR) and Big 'Falcon' spaceship (BFS) — now called "Super Heavy" and "Starship", respectively — for about $2 billion total. --martyb]


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  • (Score: 2) by Immerman on Friday December 28 2018, @05:26PM (2 children)

    by Immerman (3985) on Friday December 28 2018, @05:26PM (#779388)

    Unfortunately stable lunar orbits don't really exist - the combination of much stronger gravitational (lunar density) anomalies than on Earth, and the pull of Earth's own gravity, pretty much mean that anything in lunar orbit rapidly escapes without continuous station-keeping, which gets expensive for even a very small mountain.

    So long as you target Earth orbit up front though, there's actually a probably very large (though mostly still unidentified) number of near-earth asteroids trapped around in Earths L4 and L5 points, much as the "Greek" and "Trojan" asteroid clouds are trapped around Jupiter's. We've already identified several such asteroids that wander back and forth between our L-points and near-Earth space. It would take a relatively small amount of propulsion to deflect one of those so that it was captured by Earth - especially with the moon right there to provide a handy momentum-sinking gravitational slingshot. Just don't screw up and hit Earth.

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  • (Score: 2) by dry on Saturday December 29 2018, @06:17AM (1 child)

    by dry (223) on Saturday December 29 2018, @06:17AM (#779613) Journal

    I thought there was something like 3 stable moon orbits. Hmm, Wiki says four, https://en.wikipedia.org/wiki/Frozen_orbit#Lunar_frozen_orbits [wikipedia.org]

    • (Score: 2) by Immerman on Saturday December 29 2018, @03:52PM

      by Immerman (3985) on Saturday December 29 2018, @03:52PM (#779709)

      I suspect those are only stable compared to the alternatives - e.g. the Apollo 13 sub-satellite they mention as *almost* aligned with an optimal path lasted less than two years before electronics failure, and was believed to have crashed into the surface some time later. If you're talking about a mountain instead of a little metal box, you really want an orbit that will be stable for the long term, as corrections will be expensive. Then again it only mentions low orbits - so perhaps I misunderstood, and many stable high orbits exist.

      You also can't use a lunar slingshot to rob an incoming asteroid of much of its momentum if you're targeting lunar orbit - you pretty much need a gravity well already orbiting within your target gravity well to be able to pull that off. Without that you have to rely on rockets to neutralize the immense acceleration it gets from entering Earth space, though you could probably at least use the moon to get it into a high Earth orbit, and only use rockets for the lunar capture.