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SpaceX Pitches NASA on 'Marslink,' a Version of Starlink for the Red Planet (www.pcmag.com)

submitted 3 months ago by threelonmusketeers@sh.itjust.works to c/spacex@sh.itjust.works

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The project was mentioned during Thursday’s meeting of the Mars Exploration Program Analysis Group, which is dedicated to supporting NASA missions to the Red Planet.

In one presentation, NASA staffers talked about the space agency buying commercial services from aerospace companies to help explore Mars, according to SpaceFlight Now. This includes possibly contracting SpaceX, which currently provides its Starlink satellite internet system to over 4 million users on Earth.

Slides from the presentation show that NASA asked commercial providers to submit proposals that explained how their technology could be applied to Mars. In one slide, NASA listed a concept from SpaceX to develop “Marslink,” which would be based on Starlink satellite designs.

SpaceX’s concept was among two other ideas about developing “next-generation relay services” capable of beaming 4Mbps or more in data, but across 1.5 astronomical units, or the current distance between Mars and the Sun. This means these satellites would be able to relay data to Earth and other spacecraft across vast stretches of space, likely through Starlink's laser communication system.

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[–] ptfrd@sh.itjust.works 2 points 3 months ago (1 children)

My uneducated guesses:

Starlink's existing provision for Earth could be achieved for Mars too, using a very similar system
In some ways, Mars will be easier.
1. Much thinner atmosphere
2. Far fewer of the constraints needed to 'play nice' with an existing high-tech civilization, like minimizing reflections of sunlight to the ground, or avoiding radio interference.
But the first generation system for Mars will be different in an important way: significantly higher altitude
1. Thus higher ping times
2. And fewer satellites than would otherwise be needed for continuous coverage, which in turn means lower total bandwidth capability, and less redundancy, but much cheaper & quicker to set up and maintain.
None of the above covers the actual NASA requirement/aspiration for new interplanetary comms (which seems to be referred to as "DRM 4").
1. For one thing, an in-space laser link that can cover 100s of miles efficiently, is qualitatively different from one that can cover 100s of millions of miles.
2. But as NASA has already achieved over 6 Mbps across 240 million miles, SpaceX will also be able to create a usable interplanetary link
SpaceX will equip some of their Earth-orbiting Starlink satellites, and all of their Marslink satellites, with this qualitatively different, and outward-facing, laser comms tech.
1. Having, as your endpoints, devices that are orbiting around planets, is disadvantageous in some ways, such as the fact they spend about half the time on the wrong side.
2. But SpaceX will find a way to make it into an advantage. (Multiple simultaneous connections?)

Any thoughts?

Also, you need a relay capability when the sun is in the way. But are such relays expected to be beneficial even at other times? Will SpaceX find a way to make them beneficial?

P.S. It's interesting that Spaceflight Now did a tweet thread on this NASA presentation, but didn't consider it worth an article. Yet PC Mag made a whole article primarily out of 1/3 of a slide from one of those tweets by Spaceflight Now! (And I'm glad they did!)

[–] threelonmusketeers@sh.itjust.works 2 points 3 months ago (1 children)

Also, you need a relay capability when the sun is in the way. But are such relays expected to be beneficial even at other times? Will SpaceX find a way to make them beneficial?

If we stick some relays at the Earth-Sun L4 and L5 Lagrange points, they could potentially be used when any planet or spacecraft happens to be behind the Sun, not just Mars.

interesting that Spaceflight Now did a tweet thread on this NASA presentation, but didn’t consider it worth an article

Haha, same. I kept waiting to post SFN's own article, and it didn't come.

[–] ptfrd@sh.itjust.works 2 points 3 months ago (1 children)

Earth-Sun L4 and L5 Lagrange points

I understand these are at 60 degrees ahead of, and behind, Earth (respectively). Does anyone know how much harder it is to keep satellites at other 'offsets' from Earth? Could we realistically also have one at 30 degrees, one at 90 degrees, one at 120 degrees, and one at 150 degrees?

And could it be beneficial to send data via that route? Could they play a role analogous to something like this?:
https://en.m.wikipedia.org/wiki/Optical_communications_repeater
Or would it just be a pointless increase in latency for no benefit?

[–] threelonmusketeers@sh.itjust.works 2 points 3 months ago

Does anyone know how much harder it is to keep satellites at other 'offsets' from Earth? Could we realistically also have one at 30 degrees, one at 90 degrees, one at 120 degrees, and one at 150 degrees?

Keeping a satellite at those other 'offsets' would require a continuous supply of propellant to prevent it from drifting. L4 and L5 are special in that they theoritically need no propellant for station keeping due to orbital mechanics.

As for whether it would be useful to have satellites at these other offsets, I don't see what the advantage would be. We've already tested laser communication with the Psyche spacecraft, so I don't think repeaters would be necessary. The vacuum of space doesn't attenuate the signal that much.