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#76 2020-06-29 22:42:02

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,898

Re: GPS system for Mars?

At every decent FAA listed airfield with lighting systems, the runway lights can be turned on by a series of radio clicks, and the intensity varied by the operator. The on-surface transponders for Mars could be similarly turned on by the approaching Starship. The frequency is the common traffic frequency for the airport, or CTAF. 1 clicks turns it on, 3 clicks medium intensity, and 5 clicks for brightest runway lights. One Falcon Super Heavy could carry enough Starlink satellites converted to GPS use to place a great GPS system in place for landing
interplanetary craft.

We need in addition to the GPS system, a series of surface transponders. One each. or more,  at the desired and preselected landing sites.

Last edited by Oldfart1939 (2020-06-30 08:04:15)

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#77 2020-06-30 01:40:21

elderflower
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Registered: 2016-06-19
Posts: 1,261

Re: GPS system for Mars?

They also need to have a comms relay function. There isn't likely to be any shortwave round-the-globe communications as was used on Earth when I was young.

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#78 2020-06-30 07:04:37

tahanson43206
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Registered: 2018-04-27
Posts: 3,598

Re: GPS system for Mars?

For Oldfart1939 re #76

Thanks for your vision of what a pilot controlled landing assist system might look like on Mars.  Are there any references to suppliers, specifications or other guidelines for Mars mission planners?  Those mission planners are alive today (most likely).  Some may be working at SpaceX, but (I expect) the vast majority are still in school.

For elderflower re #77

The idea of having a ground based communications system on Mars to supplement a GPS system seems reasonable to me.  Would you be willing to develop your ideas a bit?  Is there any overlap between a communications relay system and a GPS system?  If not at present, could overlapping functions be designed into the new units to be deployed at Mars?

(th)

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#79 2020-06-30 08:06:41

Oldfart1939
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Registered: 2016-11-26
Posts: 1,898

Re: GPS system for Mars?

If SpaceX chose to do so, the Starlink satellites could double up as the planetary communication links for ground to ground communication. Maybe a half load (30 satellites) would be a feasible payload to Mars on a Falcon Heavy?

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#80 2020-06-30 08:30:14

tahanson43206
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Registered: 2018-04-27
Posts: 3,598

Re: GPS system for Mars?

For Oldfart1939 re #79

The Starlink satellites are designed for ground to ground communication on Earth, so it shouldn't be to much of a stretch (except logistically) to deploy them for that purpose on Mars. 

The question that might flow from this observation is that potentially the communications satellite network might be adapted for use as a GPS system.

The two satellite designs are coming from two completely different starting points, but convergence seems reasonable.

GPS satellites are not intended to receive traffic (except for command and control purposes), but the capabilities they provide could probably be added to communications satellites.

Edit#1: Following up a bit ... there appears to be one significant difference between a GPS satellite and a communications satellite:

Satellite Navigation Using GPS - European Space Agencywww.esa.int › esapub › bulletin › bullet90
The GPS satellites carry very stable atomic clocks that are used to derive the ... The latest receivers are inexpensive, small, offer very good performance and are ... It includes a network of ground GPS receivers, the necessary communication ...

If someone is going to all the trouble to build and deploy a communications satellite network on Mars, if seems possible (to me at least) that upgrading the satellite to include an atomic clock might not be out of the question.

(th)

Last edited by tahanson43206 (2020-06-30 11:01:03)

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#81 2020-06-30 13:43:17

Oldfart1939
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Registered: 2016-11-26
Posts: 1,898

Re: GPS system for Mars?

I implied that these satellites would be upgraded to dual purpose, and made a weight (mass) allowance for such purpose. That's why I suggested only a load of 30 of them on the Falcon Heavy loadout.

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#82 2020-06-30 13:50:50

tahanson43206
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Registered: 2018-04-27
Posts: 3,598

Re: GPS system for Mars?

For Oldfart1939 re #81

Thanks for the clarification and confirmation of a dual purpose design ... have a vendor in mind?

There ought to be engineers who would like the challenge of dual functionality!

(th)

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#83 2020-06-30 13:54:57

Oldfart1939
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Registered: 2016-11-26
Posts: 1,898

Re: GPS system for Mars?

Why not SpaceX as an in-house development?

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#84 2020-06-30 18:16:16

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: GPS system for Mars?

A falcon 9 heavy payload delivery to mars is 13,600 kg,  to 15,600 in a launch which was 60 starlink satelites of a 30 count mission seems to be on target

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#85 2020-06-30 18:44:11

tahanson43206
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Registered: 2018-04-27
Posts: 3,598

Re: GPS system for Mars?

For Oldfart1939 re #83

A wise manager hires third parties to handle needs that are not at the core of the business.

I agree that the talent assembled at SpaceX is on the order of what's needed, but my guess is they already have their hands full.

However, to my surprise, it appears SpaceX has developed its satellites in house.  Here is an article about the division possibly going public.

https://www.cnbc.com/2020/02/06/spacex- … he%20world.

Note: the URL above looks busy to my eye.  I hope it works.

That reinforces my belief that satellites are not at the core of SpaceX's business model.  They are instead a revenue driver which it would make sense to spin off.

Should that happen, the management of the new private>public company would presumably be interested in a business case for providing GPS services at Mars.

I think that GPS services are more likely a government function than a commercial one. 

***
For SpaceNut ... thanks for the lift figures you provided in #84

As a reminder, GPS satellites (and communications ones for that matter) need to be in very different orbits in order to provide full coverage of the surface of the planet they are orbiting.

My expectation is that ** each ** satellite will need its own delivery vehicle. 

Elon is able to launch 60 satellites in a batch at a time because his plan is to have hundreds of them.  Each batch is launched on a different trajectory, and then the satellites are released at intervals so they disperse over time.

That strategy would not work very well for the minimal coverage case of just 30 satellites.

(th)

Last edited by tahanson43206 (2020-06-30 18:46:29)

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#86 2020-06-30 19:17:01

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: GPS system for Mars?

http://www.nbcnews.com/id/5387135/ns/te … stem-mars/

https://space.stackexchange.com/questio … n-for-mars

https://science.slashdot.org/story/04/0 … ps-on-mars

Seems even less satellites are required
https://insidegnss.com/study-proposes-s … -for-mars/
The proposed system’s constellation of the satellites includes 15 navigation satellites in three orbital planes, each containing five satellites.

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#87 2020-06-30 19:43:41

tahanson43206
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Registered: 2018-04-27
Posts: 3,598

Re: GPS system for Mars?

For SpaceNut re #86

That is impressive work coming out of Slovakia!

The three plane system could (presumably) set up shop with only three rocket delivery vehicles.

I read that article first because of your tag line.  Perhaps the other links you provided are equally encouraging.

(th)

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#88 2020-06-30 19:48:59

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: GPS system for Mars?

Each group of 5 satellites can be made up with there own payload cruise staging booster for the ability to get to the correct orbital plane by releasing them early along the path so that they can get into the correct track before they get released into the orbits that they need to be in.

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#89 2020-07-01 22:20:10

Oldfart1939
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Registered: 2016-11-26
Posts: 1,898

Re: GPS system for Mars?

If we are discussing 3 independent sets of 5 GPS satellites and perhaps a secondary payload of orbiting comsats, then we're talking about 3 Falcon Heavy missions in 2022. The ability to throw 5 sturdy and long-lived GPS units and maybe 10 comsats per orbital plane would make sense. The Falcon Heavy costing perhaps $90 million, in addition to the cost of the various satellites. Could be less if reflown Block 5 side Boosters are used. Based on reuse of previously flown hardware, the cost of establishing a communications and GPS system on Mars could conceivably come in below $250 million.

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#90 2020-07-02 09:37:30

elderflower
Member
Registered: 2016-06-19
Posts: 1,261

Re: GPS system for Mars?

Could Spacex build and test the proposed satellites in 2 years? Probably not, but 4 years is credible for such a task if they build on the experience of others. Well maybe not then.

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#91 2020-07-02 17:12:16

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: GPS system for Mars?

With the three launches we still need way more than three landed waan systems to make it work....yes Oldfart1939, that's where I was heading with the thought of the three orbital paths...

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#92 2020-07-03 12:58:45

Oldfart1939
Member
Registered: 2016-11-26
Posts: 1,898

Re: GPS system for Mars?

The ground based systems can be activated by approaching spacecraft. The WAAS system need not be hugely massive. These could be delivered in same launch vehicles as GPS and Comsats.

Last edited by Oldfart1939 (2020-07-03 12:59:07)

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#93 2020-07-03 15:51:38

SpaceNut
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From: New Hampshire
Registered: 2004-07-22
Posts: 19,729

Re: GPS system for Mars?

Current landers similar to Insight could be a stable platform to design from for the WAAS system. That type of lander could be in the 1mt sizing which is a shipped to orbit mass in the 15mt order for what we are capable of currently. Since this is a long term running night and day device we would want to go with a similar nuclear design that is used for the rovers that are running around mars for the core power system.

So where to land and how many would we need to allow for anywhere landing of ships to come? Granted man will have specific locations that we would want but if we land enough of these around the planet I think we still can land as we would want.

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