Caption: This is a schematic of displaced geostationary orbit. Credit: Advanced Space Concepts Laboratory, University of Strathclyde
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Posted on 07/26/2010 6:43:13 AM PDT by decimon
When American space pioneer, Dr Robert L Forward, proposed in 1984 a way of greatly improving satellite telecommunications using a new family of orbits, some claimed it was impossible.
But now engineers at the University of Strathclyde's Advanced Space Concepts Laboratory have proved that Forward was right.
The late Dr Forward - a renowned physicist who worked in the United States and from his second home in Scotland - believed it was possible to use 'displaced orbits' to deploy more satellites to the north or south of the Earth's equator, helping to meet the growing demand for communications.
He proposed that the orbit of a geostationary satellite could be pushed above - or below - the usual geostationary ring around the Earth, which follows the line of the equator, by using a large solar sail propelled by the pressure of sunlight. However, critics later claimed that such 'displaced orbits' were impossible due to the unusual dynamics of the problem.
Now graduate student Shahid Baig and Professor Colin McInnes, Director of the Advanced Space Concepts Laboratory, have shown that Forward was in fact correct, in a new paper published in the Journal of Guidance, Control and Dynamics.
Professor McInnes said:"Satellites generally follow Keplerian Orbits, named after Johannes Kepler - the scientist who helped us understand orbital motion 400 years ago. Once it's launched, an unpowered satellite will 'glide' along a natural Keplerian orbit.
"However, we have devised families of closed, non-Keplerian orbits, which do not obey the usual laws of orbital motion. Families of these orbits circle the Earth every 24 hours, but are displaced north or south of the Earth's equator. The pressure from sunlight reflecting off a solar sail can push the satellite above or below geostationary orbit, while also displacing the centre of the orbit behind the Earth slightly, away from the Sun."
Although the displacement distance above or below the equator is small - of the order of 10 to 50 km - work on hybrid solar sails, which use both light pressure and thrust from a conventional electric propulsion system, is underway and aims to improve the displacement distance.
Professor McInnes added: "Other work is investigating 'polar stationary orbits', termed 'pole-sitters' by Forward, which use continuous low thrust to allow a spacecraft to remain on the Earth's polar axis, high above the Arctic or Antarctic. These orbits could be used to provide new vantage points to view the Earth's polar regions for climate monitoring."
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Shahid Baig and Professor Colin McInnes' work has been funded by the National Centre for Physics, Quaid-i-Azam University, and VISIONSPACE, an Advanced Investigator grant from the European Research Council, respectively.
The Advanced Space Concepts Laboratory is a world leader in frontier research on visionary space systems. Opened in 2009, the Laboratory's researchers are investigating how new space technologies can be used to deliver radically new space services, such as increased telecommunications capacity and new orbits for Earth observation and space science missions. More information at: www.strath.ac.uk/space
Notes to Editors:
1. The papers described in this press release are:
R L Forward, Light-levitated geostationary cylindrical orbits using perforated light sails, can be found in the Journal of the Astronautical Sciences, Vol.32, Apr-June, pp.221-226, 1984.
S Baig and C R McInnes, Light-Levitated Geostationary Cylindrical Orbits are Feasible, Journal of Guidance, Control and Dynamics, Vol. 33, No. 3, pp. 782-793, 2010.
A pre-print of the new paper is available at: http://strathprints.strath.ac.uk/18865/
Caption: This is a schematic of displaced geostationary orbit. Credit: Advanced Space Concepts Laboratory, University of Strathclyde
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Orbituary ping.
Which is code for agenda-driven science.
Shame, because the technique is interesting. However it's just going to be used for/funded by more climate garbage.
Forward himself appeared to be pretty pro capitalist in his sci fi writings. The very first sentence in Saturn Rukh is “Got a job for you, it pays a billion.”
Scots engineers prove space pioneer’s 25-year-old theory (displaced orbits for satellites)
Wait! Could there be a spaced-out connection to Displaced Immigrant Alien Travelers found in the in the Arizona wilderness by U.S. Park Rangers??
Ping.
Issac Asimov used the name Dr.Robert Forward in a humorous story,probably not the same one as in this story he made one of his usual puns with the name Forward
That was my impression as well. I really enjoyed his sci fi novels, and my first thought when he died a few years back was pretty selfish: no more new Forward novels for me to read.
In the very first page of Saturn Rukh he speaks of the “greenie organization, the peaceful planet protectors against the further development of mars”.
Just to put things in perspective: at GEO altitudes, a 50 km displacement corresponds to a truly insignificant 0.07 degrees in elevation.
They'd need to get about 10 degrees of elevation shift for this idea to have any practical utility.
I seriously doubt they're anywhere close to that.
The real use of these orbits is increasing the number of geosynchronous satellite slots by 3X. They could also provide better comsat coverage at high latitudes.
The ref to climate change was probably put in by some NASA PR twinkie.
The basic science is not “agenda driven”; it is really useful science for comm apps.
BTW, I had the honor of meeting Dr. Forward and contributing to one of his projects in a minor way. He had a contract from USAF to check out inertialess drives and other far-out space propulsion ideas.
He found that almost all of the novel ideas were BS or violated the laws of physics. However, he found two winners: tethers and antimatter drives. Either of those could revolutionize space travel.
If you’re going to keep station over a pole, you’re going to be sitting there with no orbital momentum. This means that the always-present weight vector, pointing at the center of the earth, will have to be counteracted with an equal amount of upward thrust from some source or another, for the entire lifetime of the satellite.
(Of course, the higher the altitude, the less the weight for a given mass, and therefore the less the required thrust.)
It’s by no means obvious how they can utilize solar pressure in the polar sitting-case, since its force is always directed at 90 +/- 22 degrees from the needed direction. Converting that force into thrust using an ion engine, for instance, that could (1) Counteract the sunlight force itself, and (2) Provide levitating force equal to the weight of the satellite, would seem to violate the laws of Physics.
I can conclude only that they are assuming the presence consumable fuels onboard. But how long could such a satellite remain on station given the levitating impulse (thrust * time) available from any present or achievable or proposed, thruster technology? In terms of thrust alone, no presently achievable ion engine would even be close to supporting its own weight (even at, say, 40 000 KM), much less the weight of a practical satellite.
** Side note: Let us define a “classical” orbit as being one where the satellite is not subjected to external forces. This means that the orbit will be planar, with one focus at the center of the earth. (This leaves aside the secondary effects of solar pressure, drag from micro-atmosphere, and tidal irregularities from the earth, moon, and other massive objects.)
Now consider the case of a geosynchronous orbit in the plane of the equator. To “levitate” this orbit so that it follows a line of latitude away from the equator takes increasing amounts of thrust (power). The extreme case is considered above; viz., the polar-sitting case.
I’m really annoyed that the author uses “Geostionary” when they should use “Geosynchronous”.
Yeah I learned about the nanotube thethers from his fiction. Very interesting and novel idea for climbing into and out of gravity wells.
Does this really “prove” anything? Seems to me a satellite with a solar sail in a stable orbit would be a lot more like “proof.”
Isn’t the EIB Satellite in “Geosynchronous Orb”?
Who else where ye' expectin'?
CC
” a conventional electric propulsion system”
um...that is going to take a long extension cord...
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