Author Topic: SpX Mars Communication Constellation?  (Read 13173 times)

Offline swervin

  • Full Member
  • *
  • Posts: 165
  • Viper Driver
  • GA
  • Liked: 43
  • Likes Given: 9
SpX Mars Communication Constellation?
« on: 04/16/2018 07:30 AM »
As SpX gears up to head to Mars in the relative near-ish future (big pic, as compared to the 50 years its been since we visited the Moon), and w/ even NASA mitigating their comm plans for future exploration craft through mission extensions and crossed-fingers, has anyone seen or heard of SpX utilizing Starlink-like spacecraft for Mars communication requirements? i.e., a 'Mars Iridium' constellation, if you will. Seems w/ humans going to Mars, comms need to be assured or as redundant as possible.

This could even be seen as a valid commercial partnership/opportunity with NASA, ESA, or name-a-space-agency that wants to send exploration craft/humans to Mars. Early commercial use for NASA could be a great way to test out a more robust concept/capabilities (MarsLink Gen 1, or whatever it is called), and incorporate those into Gen 2, etc.

Anyone care to venture a guess of how many satellites it would take for adequate coverage? What is adequate coverage? How many Starlink-sized satellites could a F9H (presumption) loft to Mars on a single mission? How many F9H's would be required (in total) for X number of satellites? Min number of satellites to establish an initial operating capability at Mars?

Perhaps the top 5 requirements for a system like this, from those of you on here who are smarter than I!

Cheers,
Splinter

Mods: I did some searches and didn't see this topic specifically addressed or have it's own thread. Sorry if I overlooked any posts and please feel free to incorporate this post/thread elsewhere if I missed something.

Offline speedevil

  • Senior Member
  • *****
  • Posts: 2591
  • Fife
  • Liked: 1298
  • Likes Given: 1415
Re: SpX Mars Communication Constellation?
« Reply #1 on: 04/16/2018 08:53 AM »
As ballpark numbers.
Mars is smaller than earth, and has a somewhat lower population of internet users.
This can be adequately served currently by 0 satellites, weighing 0 tons, and costing 0 to deliver.

More seriously.
Starlink will, at the time of first serious attempt at throwing stuff at Mars - 2022 - have available 500kg or so satellites, that can communicate within perhaps a thousand kilometers optically.
The intended earthly constellation is run at 1200km, for the further out satellites.

In order to have several in view at once, at that altitude over Mars, somewhere slightly over 24 would be needed.
Plus perhaps four of these equipped with large LASER links back to the starlink constellation on earth.

This would give 'broadband' coverage easily to a few thousand people/drones on Mars.
The link to earth would be quite constrained, at least at first.

But, it's plausible to start out with a communications constellation initially weighing around 25 tons maximum, including fuel to trim their final orbits.

BFS comes in, with around 180 tons of payload total, skips off the top of the atmosphere dumping a couple of kilometers a second speed, and then drops the 30 tons of satellites + dispenser, and then proceeds to land.

The same network can of course have assorted useful sensors and small telescopes, perhaps doubling as the communication links back to earth.

It of course also means that special purpose martian satellites to run a small telescope, or monitor the atmosphere, or guide a large tank to Mars ... cost $1M or so to produce, not $100M, as you already have essentially all of the satellite pre-designed, and just have to stick on a sensor.

« Last Edit: 04/16/2018 08:54 AM by speedevil »

Offline swervin

  • Full Member
  • *
  • Posts: 165
  • Viper Driver
  • GA
  • Liked: 43
  • Likes Given: 9
Re: SpX Mars Communication Constellation?
« Reply #2 on: 04/16/2018 09:58 AM »
Ha. Good initial wit, speedevil!

Valid points though, and I was also thinking the laser link would be a requirement. Secondly, I had not thought about dual-use of the sats. Mars colonists would like to have at least some 'Mars weather' monitoring capability, I would think. Possibly other dual uses...

I wasn't so much thinking about this as 'broadband' service on Mars, but more of a link to Earth, writ large, and more of a comm/data relay for anything on/around/entering Mars' atmosphere, such as arriving EDL needs of NASA or other space agencies, not to mention SpX's EDL needs. I use the Starlink sat's as an example and an in-house capability SpX is building that may be adaptable.

Splinter

Re: SpX Mars Communication Constellation?
« Reply #3 on: 04/16/2018 11:43 AM »
I think another reason to send many Starlink sats, also instrumented for high resolution surface imaging would be to have very detailed surface mapping to chose the landing sites.
I heard that, as of 2 years ago, only 3% of Mars' surface was mapped with sufficient detail, how is the situation now? Is the current resolution (and extension) of mapped areas enough to evaluate the morphology of potential landing sites, locate in situ resources accurately and support human missions? Would <1m per pixel resolutions, something like WorldView, but for Mars, be necessary to select the projected 2022 uncrewed landing site?

Failure is not only an option, it's the only way to learn.
"Tradition is not the worship of ashes, but the custody of fire" - Gustav Mahler

Offline MrHollifield

  • Member
  • Posts: 60
  • Charleston, SC USA
  • Liked: 18
  • Likes Given: 44
Re: SpX Mars Communication Constellation?
« Reply #4 on: 04/16/2018 12:12 PM »
Instead of putting lasers on primary constellation satellites for Earth relay, what about 1 to 4 satellites in areocentric (is that the right word?) orbit? Granted the first few years will have just one location so long haul Mars-to-Mars calls won't be plentiful, but if you want to set the system up for a large, dispersed population, why not have the capability from the start.


To ensure comms with Earth during conjunctions, do you want to add a relay at ESL4 or ESL5? MSL4 or MSL5?

Offline speedevil

  • Senior Member
  • *****
  • Posts: 2591
  • Fife
  • Liked: 1298
  • Likes Given: 1415
Re: SpX Mars Communication Constellation?
« Reply #5 on: 04/16/2018 12:53 PM »
Instead of putting lasers on primary constellation satellites for Earth relay, what about 1 to 4 satellites in areocentric (is that the right word?) orbit? Granted the first few years will have just one location so long haul Mars-to-Mars calls won't be plentiful, but if you want to set the system up for a large, dispersed population, why not have the capability from the start.

The above does have that capability.
24 or so satellites, of basically identical configuration to earth Starlink ones, will, with software changes only, and a tiny bit more thermal insulation, give hundreds of megabits at least communication with under 100ms latency between any two points on Mars, with a few kilograms and a few tens of watts power on the ground.

Or, indeed, to the visible sides of the moons.



Offline Jet Black

Re: SpX Mars Communication Constellation?
« Reply #6 on: 04/16/2018 12:58 PM »
I heard that, as of 2 years ago, only 3% of Mars' surface was mapped with sufficient detail, how is the situation now? Is the current resolution (and extension) of mapped areas enough to evaluate the morphology of potential landing sites, locate in situ resources accurately and support human missions? Would <1m per pixel resolutions, something like WorldView, but for Mars, be necessary to select the projected 2022 uncrewed landing site?

On this, there are quite a few low cost imaging and radar satellites coming in to play now. I think the low cost of satellite launches that SpaceX are bringing to the market stand to really improve innovation in this area, which as a side effect benefits mars, even if SpaceX end up buying someone elses satellites to take to mars.
For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled. -- Richard Feynman

Offline guckyfan

  • Senior Member
  • *****
  • Posts: 6757
  • Germany
  • Liked: 1790
  • Likes Given: 1766
Re: SpX Mars Communication Constellation?
« Reply #7 on: 04/16/2018 06:05 PM »
Using a higher altitude than on earth could reduce the number of needed satellites to less than 10. Fast ping times are not critical at this time on Mars.

Re: SpX Mars Communication Constellation?
« Reply #8 on: 04/16/2018 06:43 PM »
I heard that, as of 2 years ago, only 3% of Mars' surface was mapped with sufficient detail, how is the situation now? Is the current resolution (and extension) of mapped areas enough to evaluate the morphology of potential landing sites, locate in situ resources accurately and support human missions? Would <1m per pixel resolutions, something like WorldView, but for Mars, be necessary to select the projected 2022 uncrewed landing site?

On this, there are quite a few low cost imaging and radar satellites coming in to play now. I think the low cost of satellite launches that SpaceX are bringing to the market stand to really improve innovation in this area, which as a side effect benefits mars, even if SpaceX end up buying someone elses satellites to take to mars.

True, I brought this up because there were mentions of remote sensing applications in Starlink's filings, if I'm not mistaken.
Failure is not only an option, it's the only way to learn.
"Tradition is not the worship of ashes, but the custody of fire" - Gustav Mahler

Online philw1776

  • Full Member
  • ****
  • Posts: 1076
  • Seacoast NH
  • Liked: 696
  • Likes Given: 303
Re: SpX Mars Communication Constellation?
« Reply #9 on: 04/16/2018 07:27 PM »

I heard that, as of 2 years ago, only 3% of Mars' surface was mapped with sufficient detail, how is the situation now? Is the current resolution (and extension) of mapped areas enough to evaluate the morphology of potential landing sites, locate in situ resources accurately and support human missions? Would <1m per pixel resolutions, something like WorldView, but for Mars, be necessary to select the projected 2022 uncrewed landing site?

Excellent point.  In NASA's recent Mars Landing Workshop

https://www.nasa.gov/feature/mars-human-landing-site-workshop-presentations

advocates for each target landing site in closing each made the point that existing data is way too sparse and ambiguous concerning the viability of each site.  I maintain that SpaceX needs to update their game plan with some sort of survey mission(s) before landing expensive BFS cargo ships ready for ISRU that may not be sufficiently accessible.
“When it looks more like an alien dreadnought, that’s when you know you’ve won.”

Re: SpX Mars Communication Constellation?
« Reply #10 on: 04/16/2018 07:41 PM »

I heard that, as of 2 years ago, only 3% of Mars' surface was mapped with sufficient detail, how is the situation now? Is the current resolution (and extension) of mapped areas enough to evaluate the morphology of potential landing sites, locate in situ resources accurately and support human missions? Would <1m per pixel resolutions, something like WorldView, but for Mars, be necessary to select the projected 2022 uncrewed landing site?

Excellent point.  In NASA's recent Mars Landing Workshop

https://www.nasa.gov/feature/mars-human-landing-site-workshop-presentations

advocates for each target landing site in closing each made the point that existing data is way too sparse and ambiguous concerning the viability of each site.  I maintain that SpaceX needs to update their game plan with some sort of survey mission(s) before landing expensive BFS cargo ships ready for ISRU that may not be sufficiently accessible.
Maybe they think they've got sufficient data, at least for initial missions, or maybe there are some unannounced plans.

Thanks however, I was looking for a resource like this!
Failure is not only an option, it's the only way to learn.
"Tradition is not the worship of ashes, but the custody of fire" - Gustav Mahler

Offline CuddlyRocket

Re: SpX Mars Communication Constellation?
« Reply #11 on: 04/16/2018 08:04 PM »
Anyone care to venture a guess of how many satellites it would take for adequate coverage? What is adequate coverage? ... Min number of satellites to establish an initial operating capability at Mars?

First question: Do you need a satellite communications constellation? Especially in the early days of manned operations and later a colony. (Eventually a growing colony will probably want a satellite constellation, but you can let them design it!) Sure, such a thing is desirable, but do you actually need it. Such things cost money. Money which might be better spent elsewhere. So don't put the cart before the horse. Decide what communications you're going to need and then decide how to meet that need.

One thing to take into account is that even with humans on Mars there will probably still be scientific satellites in orbit, many of which will have their own communications capability, which can be possibly be co-opted.
« Last Edit: 04/16/2018 08:05 PM by CuddlyRocket »

Offline geza

  • Full Member
  • **
  • Posts: 215
  • Budapest
    • Géza Meszéna's web page
  • Liked: 65
  • Likes Given: 33
Re: SpX Mars Communication Constellation?
« Reply #12 on: 04/16/2018 08:06 PM »
Initially, 3 synchronous satellite can provide the necessary connectivity and navigation everywhere, incl. EDL support, except the polar regions. Because of the higher distance, the Starlink satellites can provide much lower bandwidth, but it will sufficient for the few people and few vehicle; latency is a nuisance.

Probably they will not want to maneuver a BFS to synchronous orbit and land it after that. Instead BFS will release the satellites before arriving to Mars. They will maneuver themselves first from the incoming hyperbolic orbit to the synchronous transfer orbit and then to synchronous orbit. The DeltaV is not that much.   

   

Offline AncientU

  • Senior Member
  • *****
  • Posts: 6217
  • Liked: 4008
  • Likes Given: 5546
Re: SpX Mars Communication Constellation?
« Reply #13 on: 04/16/2018 08:20 PM »
Ha. Good initial wit, speedevil!

Valid points though, and I was also thinking the laser link would be a requirement. Secondly, I had not thought about dual-use of the sats. Mars colonists would like to have at least some 'Mars weather' monitoring capability, I would think. Possibly other dual uses...

I wasn't so much thinking about this as 'broadband' service on Mars, but more of a link to Earth, writ large, and more of a comm/data relay for anything on/around/entering Mars' atmosphere, such as arriving EDL needs of NASA or other space agencies, not to mention SpX's EDL needs. I use the Starlink sat's as an example and an in-house capability SpX is building that may be adaptable.

Splinter

You should be. 
While you're at it, think in terms of Mars and the Moon.

Broadband service won't be for kitty videos and Netflix, but for a real-time internet of things and users... mostly the former at first.  SpaceX is a Silicon Valley company which thinks in terms of universal, continuous connectivity, not minimalist communications or relays of science data via orbiting science satellites to an expensive deep space network on Earth.  Plan on every device (humans are just complicated devices) on the planet being in continuous, broadband communication with every other...

The laser sat link to Earth possibly works from Starlink-like satellites, but that won't cut it in reverse.  Need large (several meter aperture) telescope receiver at each end to establish dual direction, high bandwidth link.  Starlink constellation can handle the Earth-side uplink and downlink with the relay satellites.  This also establishes a capability to provide positional information to ships making way to/from Mars.  These interplanetary laser tracking and data relay satellites should eventually be in GSO, Earth-Sun L-4 and/or 5, and ASO -- this distribution could provide better positional and tracking data for anywhere in the Solar System than ever before available due to the long baseline and multiple lines of sight.
"If we shared everything [we are working on] people would think we are insane!"
-- SpaceX friend of mlindner

Offline DistantTemple

  • Full Member
  • **
  • Posts: 270
  • England
  • Liked: 156
  • Likes Given: 286
Re: SpX Mars Communication Constellation?
« Reply #14 on: 04/16/2018 10:42 PM »
I've (also) just been reading https://www.nasa.gov/journeytomars/mars-exploration-zones particularly  a paper on mining water for ISRU.

The biggest current problem is lack of data, including hi res visual, and other remote sensing. The only good detail is from the rovers, MSL etc.

I bet we see a FH mission or two in 2020, to place satellites mainly for detailed remote sensing for site selection and planning. These will have comms capability. However the first BFS's in 2022 appears be an ideal time to set up the start of a mars net, and main earth relay. (And it'd be great if SX placed a rover! Which would make perfect sense if they have a favourite base location, to get detailed answers about water, resources, where to set BFR's down etc.)

These 2022 arrivals reported purpose, is to set up ISRU fuel production. There is opinion that ISRU should be working well before humans arrive, so it is critical path technology.

Some of the robotic operations will need to be quite accurate, following "roads", laying/burying  cables in specific places, dumping in hoppers, avoiding bumping into equipment whilst needing to manoeuvre close to it. For this radio beacons can be placed, and/or a GPS like system can be set up. (AI and sight may well complement this, but will be secondary) If some of these beacons will be some miles away, behind hills, or in valleys, then comms via satellite, if available would be very convenient. Also the operation will (I assume) combine autonomous operation with human oversight and issue resolution from Earth. All the equipment will need to communicate fairly seamlessly and reliably between items. Therefore excellent comms both local and to Earth are very important. You don't want to be waiting hours till the satellite goes over to see if the a rover is correctly orientated to the spoil hopper before unloading! Or to find it aborted autonomous mode 1 minute after you last lost contact.

If the ISRU fails before 2024, and communications could have "saved" it, that's a powerful reason to having at least several satellites in place covering the ISRU site, and relay to earth.

So remote sensing and minimal Comms on FH's in 2020 (+ rover please Elon), Then functional network, particularly over landing site, and link to Earth with the BFR's in 2022 ... then .... crystal ball.

Most of this is just my opinion. I agree with relays at Lagrange points etc, larger dishes etc... and
Quote from: geza
Probably they will not want to maneuver a BFS to synchronous orbit and land it after that. Instead BFS will release the satellites before arriving to Mars. They will maneuver themselves first from the incoming hyperbolic orbit to the synchronous transfer orbit and then to synchronous orbit. The DeltaV is not that much. 
makes perfect sense.
« Last Edit: 04/16/2018 10:45 PM by DistantTemple »
We can always grow new new dendrites. Reach out and make connections and your world will burst with new insights. Then repose in consciousness.

Offline biosehnsucht

  • Full Member
  • **
  • Posts: 287
  • Liked: 94
  • Likes Given: 146
Re: SpX Mars Communication Constellation?
« Reply #15 on: 04/16/2018 10:43 PM »
But, it's plausible to start out with a communications constellation initially weighing around 25 tons maximum, including fuel to trim their final orbits.

BFS comes in, with around 180 tons of payload total, skips off the top of the atmosphere dumping a couple of kilometers a second speed, and then drops the 30 tons of satellites + dispenser, and then proceeds to land.

If they get the chomper ready for the first pair of BFS to land at Mars (to carry needed stuff for ISRU), perhaps they can chomper-deploy the dispenser, then use the now-empty cargo space for inflatable tanks for ISRU? So the volume doesn't go to waste even after "losing" 30 tons of cargo to surface.

Actually, depending on the remaining cargo to surface and it's density, and if they do any in-orbit transfer, perhaps they can still land the full amount of cargo - just starting out with 30 tons more than they could land, which they deploy before landing to get under landing mass.

Re: SpX Mars Communication Constellation?
« Reply #16 on: 04/16/2018 11:22 PM »
A question related to this: could a chomper BFR deploy a sizable amount of payload (let's say 20 tons) in martian orbit and come back? If I had to guess I'd say that it could by refueling in HEO, but I'm no expert.
Also: could it go to Mars orbit and come back to Earth in 6 months, if launched at the beginning of the window?

If possible, this kind of mission would also be a good test for guidance, communications and to see how the spaceship behaves in long duration, several months long flights.
Failure is not only an option, it's the only way to learn.
"Tradition is not the worship of ashes, but the custody of fire" - Gustav Mahler

Online FishInferno

  • Full Member
  • *
  • Posts: 103
  • Liked: 58
  • Likes Given: 100
Re: SpX Mars Communication Constellation?
« Reply #17 on: 04/16/2018 11:37 PM »
A question related to this: could a chomper BFR deploy a sizable amount of payload (let's say 20 tons) in martian orbit and come back?

Probably not, but presumably BFR should be able to land on Mars, refuel, launch something to Martian orbit and then land back on Mars to refuel for the trip home.
Comparing SpaceX and SLS is like comparing paying people to plant fruit trees with merely digging holes and filling them.  - Robotbeat

Offline DistantTemple

  • Full Member
  • **
  • Posts: 270
  • England
  • Liked: 156
  • Likes Given: 286
Re: SpX Mars Communication Constellation?
« Reply #18 on: 04/16/2018 11:45 PM »
A question related to this: could a chomper BFR deploy a sizable amount of payload (let's say 20 tons) in martian orbit and come back? If I had to guess I'd say that it could by refueling in HEO, but I'm no expert.
Also: could it go to Mars orbit and come back to Earth in 6 months, if launched at the beginning of the window?

If possible, this kind of mission would also be a good test for guidance, communications and to see how the spaceship behaves in long duration, several months long flights.
Depending on the speed you leave Earth... I believe the mars journey can be a "free return" orbit, coming back to earth some months later, with no other burns!
As 
Quote from: AbuSimbel
Also: could it go to Mars orbit and come back to Earth in 6 months, if launched at the beginning of the window?
says.
So if the satellites in their dispenser, and other cargoes, were all deployed as the BFS approached mars, the BFS would carry on back to Earth, and the various cargoes would all begin their missions. It would suit landing items away from the main base, such as other rovers. Its the sort of complication that SX might not like as it involves separate thruster and EDL arrangements, for each part. Maybe it could even deploy a Dragon containing rovers... as that already is designed for EDL. !
We can always grow new new dendrites. Reach out and make connections and your world will burst with new insights. Then repose in consciousness.

Offline CuddlyRocket

Re: SpX Mars Communication Constellation?
« Reply #19 on: 04/17/2018 08:31 PM »
Broadband service won't be for kitty videos and Netflix, but for a real-time internet of things and users... mostly the former at first.  SpaceX is a Silicon Valley company which thinks in terms of universal, continuous connectivity, not minimalist communications or relays of science data via orbiting science satellites to an expensive deep space network on Earth.  Plan on every device (humans are just complicated devices) on the planet being in continuous, broadband communication with every other...

SpaceX may very well think in those terms; but they may also possibly forget just how much investment in equipment and manpower is needed to maintain that connectivity (which in any case is mainly provided by short range radio links and cables of one sort and another).

Quote
The laser sat link to Earth possibly works from Starlink-like satellites, but that won't cut it in reverse.  Need large (several meter aperture) telescope receiver at each end to establish dual direction, high bandwidth link.  Starlink constellation can handle the Earth-side uplink and downlink with the relay satellites.  This also establishes a capability to provide positional information to ships making way to/from Mars.  These interplanetary laser tracking and data relay satellites should eventually be in GSO, Earth-Sun L-4 and/or 5, and ASO -- this distribution could provide better positional and tracking data for anywhere in the Solar System than ever before available due to the long baseline and multiple lines of sight.

Jeez, how much is all this going to cost? This is the Battlestar Galactica of communications infrastructure; grossly over-engineered for what will be needed in the early stages. Most personnel for most of the time will be near or in the base or colony; in which case wi-fi supplemented by cable together with its own high-powered directional antenna (for direct link to Earth) will suffice for the vast majority of needs.

Tags: