IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
Shackelton Station - Earth communication
paranoid123
post Dec 1 2006, 01:18 AM
Post #1


Newbie
*

Group: Members
Posts: 6
Joined: 31-October 06
Member No.: 1305



I just read this press release about having relay satellites in "stable" lunar orbits for continuous Earth - Shackleton Station communication.

http://science.nasa.gov/headlines/y2006/30nov_highorbit.htm

It says "High-inclination, highly elliptical orbits being cheapest and most stable for communications satellites around the Moon? To Earth-centered satellite engineers used to thinking in terms of circular equatorial orbits, "it's a new paradigm," Ely declares."

Now, I'm no engineer or designer or anything, but wouldn't several line of sight relay stations, or probably a really really long fiber optic to a transmitter placed somewhere on the moon that faces the earth be much cheaper than the launch and operations of three relay satellites?

Or am I reading too much into this article?
Go to the top of the page
 
+Quote Post
Guest_AlexBlackwell_*
post Dec 1 2006, 01:25 AM
Post #2





Guests






QUOTE (paranoid123 @ Nov 30 2006, 03:18 PM) *
Now, I'm no engineer or designer or anything, but wouldn't several line of sight relay stations, or probably a really really long fiber optic to a transmitter placed somewhere on the moon that faces the earth be much cheaper than the launch and operations of three relay satellites?

How exactly are you going to place all of that infrastructure on the lunar surface? Call me crazy, but I'll assume you'll have to launch and land on the lunar surface, then complete the assembly, either robotically or by humans. And you think that's cheaper than placing three satellites into lunar orbit?
Go to the top of the page
 
+Quote Post
Phil Stooke
post Dec 1 2006, 01:30 AM
Post #3


Solar System Cartographer
****

Group: Members
Posts: 10127
Joined: 5-April 05
From: Canada
Member No.: 227



Aren't those elliptical orbits basically the kind the Russians have used for a long time? - Molniya orbits? Hardly a new paradigm, if so. But I don't know much about this.

Phil


--------------------
... because the Solar System ain't gonna map itself.

Also to be found posting similar content on https://mastodon.social/@PhilStooke
NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
Go to the top of the page
 
+Quote Post
Guest_AlexBlackwell_*
post Dec 1 2006, 01:34 AM
Post #4





Guests






QUOTE (Phil Stooke @ Nov 30 2006, 03:30 PM) *
Aren't those elliptical orbits basically the kind the Russians have used for a long time? - Molniya orbits? Hardly a new paradigm, if so. But I don't know much about this.

You're right, high-inclination elliptical orbits for communications (or even SIGINT, e.g., NRO Jumpseat spysats) is nothing new. And the now-defunct Mars Telecom orbiter (and even earlier iterations of Marsat constellations) had similar orbits as an alternative architecture to areostationary monitoring.

There are tradeoffs, but that's show biz biggrin.gif
Go to the top of the page
 
+Quote Post
helvick
post Dec 1 2006, 09:57 AM
Post #5


Dublin Correspondent
****

Group: Admin
Posts: 1799
Joined: 28-March 05
From: Celbridge, Ireland
Member No.: 220



QUOTE (AlexBlackwell @ Dec 1 2006, 01:25 AM) *
And you think that's cheaper than placing three satellites into lunar orbit?

[A] Line of sight relays. Assuming 4m masts you will need one surface relay station every 5km or so. You'll need to come down to around 70N or so. My back of the Envelope calculations makes that around 115 relays. Each of those has to be landed, commissioned and powered for the duration of the mission. A mass of around 500kg per relay seems optimistic to me but even at that we are talking about delivering close to 60 tons to the lunar surface with extremely precise positioning.

[B] Run a cable of some sort from the base to a main Earth Relay station at 70N (or thereabouts). Single armoured submarine comms cables come it at around 5 tons per km. Even assuming that we could do a lunar comms cable for two orders of magnitude less than this you are still talking about laying 30tons of cable across 600km of the lunar surface and getting all that mass to the lunar surface safely (along with the laying equipment).

[C] 3 x Molniya type satellites in lunar orbit. These would probably weigh in the region of 500-1000kg.

Practicality and cost are directly related to the amount of mass you need to use - the satellite solution is cheaper and easier by at least an order of magnitude.
Go to the top of the page
 
+Quote Post
djellison
post Dec 1 2006, 10:16 AM
Post #6


Founder
****

Group: Chairman
Posts: 14431
Joined: 8-February 04
Member No.: 1



QUOTE (helvick @ Dec 1 2006, 09:57 AM) *
- the satellite solution is cheaper and easier by at least an order of magnitude.


Several infact. $800m will build, launch and upgrade groundstations for three TDRS sat's which can each do 400 (or even 800) Mbps from GEO - $250m..ish..each. You'd drop some of the bandwidth - but a TDRS asset plased at some sort of L2 point would probably make most of the problem go away, for something like $400m including launch and augmentation of the bus for a greater fuel load and a larger LV to get it off the ground.

In the new mould of COTS etc...I would personally have thought that this is something that could be just handed to one of the big Sat manufacturers with a big cheque and told "make it so"

Doug
Go to the top of the page
 
+Quote Post
Phil Stooke
post Dec 1 2006, 04:43 PM
Post #7


Solar System Cartographer
****

Group: Members
Posts: 10127
Joined: 5-April 05
From: Canada
Member No.: 227



"Line of sight relays. Assuming 4m masts you will need one surface relay station every 5km or so. "

Not so many, bacause you wouldn't measure to a flat horizon (as that must assume), you would naturally transmit from peak to peak - for instance, I think Schrunk and others have shown Malapert Mountain is within line of sight of Shackleton rim, 5 degrees or 150 km away. With good planning you might only need 5 or 6 relays.

I still prefer satellites, though, just making a point.

Phil


--------------------
... because the Solar System ain't gonna map itself.

Also to be found posting similar content on https://mastodon.social/@PhilStooke
NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
Go to the top of the page
 
+Quote Post
helvick
post Dec 1 2006, 06:16 PM
Post #8


Dublin Correspondent
****

Group: Admin
Posts: 1799
Joined: 28-March 05
From: Celbridge, Ireland
Member No.: 220



QUOTE (Phil Stooke @ Dec 1 2006, 04:43 PM) *
I still prefer satellites, though, just making a point.

Good point. I am compelled to add as a parting shot that however difficult landing a series of relays out on a lunar plain might be I suspect that landing a handful on the peaks of the four or five tallest Lunar mountains around the pole would be quite an interesting challenge.

smile.gif
Go to the top of the page
 
+Quote Post

Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 28th March 2024 - 10:42 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.