PhysOrg: Scots engineers prove space pioneer's theory

[bystander]

Scots engineers prove space pioneer's 25-year-old theory
University of Strathclyde | PhysOrg | Space Exploration | 26 July 2010

[b]This is a schematic of displaced geostationary orbit. [i]Credit: Advanced Space Concepts Laboratory, University of Strathclyde[/i][/b]

---

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.

Light levitated geostationary cylindrical orbits are feasible - S Baig, CR McInnes

• Journal of Guidance, Control and Dynamics 33(3) (May-June 2010) doi: 10.2514/1.46681 (preprint)

Why light-levitated geostationary cylindrical orbits are not feasible- HJ Fischer, A Haerting

• Journal of the Astronautical Sciences 40(3) (Sept 1992)

Light-Levitated Geostationary Cylindrical Orbits: Correction and Expansion - RL Forward

• Journal of the Astronautical Sciences 38(3) (Sept 1990)

Light-Levitated Geostationary Cylindrical Orbits Using Perforated Light Sails - RL Forward

• Journal of the Astronautical Sciences 32(2) (June 1984)

Light-Levitated Geostationary Cylindrical Orbits - RL Forward

• Journal of the Astronautical Sciences 29(1) (Mar 1981)

[Chris Peterson]

Interesting. But I'd consider it a misnomer to refer to such a spacecraft trajectory as an "orbit".

[rstevenson]

Interesting. But I'd consider it a misnomer to refer to such a spacecraft trajectory as an "orbit".

I suspect this is one of those arguments you'll lose in the long run. If we ever achieve the technology to do this sort of thing easily (and it seems we're beginning to do just that), the concept of orbit will just be conflated with the concept of trajectory, and we'll speak of powered "orbits". (As opposed to, say, "Light levitated geostationary cylindrical orbits". ) And then, after awhile, we'll drop the quote marks. Language evolving, as always.

Rob

[Chris Peterson]

Interesting. But I'd consider it a misnomer to refer to such a spacecraft trajectory as an "orbit".

I suspect this is one of those arguments you'll lose in the long run. If we ever achieve the technology to do this sort of thing easily (and it seems we're beginning to do just that), the concept of orbit will just be conflated with the concept of trajectory, and we'll speak of powered "orbits". (As opposed to, say, "Light levitated geostationary cylindrical orbits". :shock: ) And then, after awhile, we'll drop the quote marks. Language evolving, as always.

It's not even an argument I'd engage in. My first response on seeing the picture was "this is impossible". And indeed, it is... if we're talking about ballistic orbits. If you are able to pump energy into the system, of course, you can follow any sort of path you like.

English is flexible, and certainly one meaning of "orbit" is simply "to go around". So in some senses, a "light levitated orbit" is still an "orbit". But I'd hope that if things like this ever become common, people have the sense to apply the right modifiers.

[neufer]

It makes so much more sense to have an entire fleet of:

• quasi-equatorial
  quasi-circular (~35,786 km semi-major axis)

redundant quasi-geostationary satellites =>

Even the poles would be covered by the satellite procession
passing through one of the quasi-fixed "solstice" points.