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§ 3.4.2 Interorbital Lightsails

Like wind, sunlight exerts pressure. This pressure is so "light", or gentle, that humans don't feel it. However, in orbital space, if you make a large sail out of thin aluminum reflective material, you can go places without any propellant, merely using the pressure of the sun. However, you need to control your sails so that you go where you want to go.

Going away from the Sun, you tilt the sail at an angle of approximately 35 degrees, since achieving a higher orbit is a combination of being pushed away from the sun and picking up angular momentum (orbital speed at the moment). You can go in towards the sun, too, by pointing your sails at an angle so that you slow down your orbital speed in order for the sun's (or Earth's) gravity to pull you inward. Thus, you have flexibility in maneuvering, assuming you have well designed sails.

Notably, going straight out from the Sun is not useful for achieving into a higher orbit, and just makes your orbit more elliptical, passing back through the point where it was when the sail was deployed. The component of force which increases angular momentum is what produces useful changes to orbital parameters.

Light sails are perhaps better known as "solar sails". However, the phrase "solar sails" is often confused with "solar cells", two very different technologies. This is compounded by different international accents. Indeed, within the USA, my southern accent confuses people in the northeast US on this phrase. Both phrases are used in the literature, and I use the minority phrase "light sail".

The following links give information on Light Sails:

U3P has a nice layman's explanation of the concept of solar sailing as well as its scientific history, on their beautiful Solar Sails website, which also includes animations, images, specific papers and more web links. Also covers Znamya, the Russian in-space solar sail experiments. Multiple language translations. (U3P means Union for the Promotion of Photonic Propulsion.)

Benjamin Diedrich's Solar Sails page, which includes a great list of web links, books, articles & reports, and people, as well as explanations of the concepts (though not most basic).

In addition to the Russian Znamya effort, commercial lightsails could come sooner than expected if the InterWorld Transport's Commercial Solar Sailing R&D Project is commercially successful. This is a serious hardware project.

Manfred Leipold has a Solar Sail page at the German Aerospace Center (DLR) The DLR has investigated the feasibility of solar sail technology and assessed several deep-space mission scenarios utilizing solar sail propulsion over the last 5 years. Recently, a feasibility study on a low-cost solar sail technology demonstration mission in Earth orbit was conducted cooperatively by DLR and NASA/JPL (Jet Propulsion Laboratory). Currently, a breadboard model of a fully deployable sail structure is being developed for ground demonstration purposes and testing on a co-funding basis between DLR and ESA.

A UKSEDS (U.K. Students for the Exploration and Development of Space) page entitled The Microlight Solar Sail talks of past and potential student projects. (SEDS is Students for Exploration and Development of Space.)

The physics of solar sailing is also discussed in a page by Christopher Neufeld (Canada). > Transportation > Midterm > Lightsails


PERMANENT needs a PHP / MySQL (actually, MariaDB) programmer. Are you a PHP / MySQL programmer interested in getting into space development as a career, or already working in space development? Or do you know somebody else who might be interested?

There is an ongoing process to update this website in 2019 with a target relaunch in 2020.
This website is actually very out of date. Much of the website text content was written in the 1980s to early 2000s, but that's a different matter. As regards PHP / MySQL, some offline databases go into the 2010s, as regards professional publications, engineers, companies, etc., and this is what we need programming help with. We are updating our databases on people, organizations, publications, and other things, for open source space development for all.

The current status is we have some working databases which we have been using internally for a long time for organizing professional publications, and to track people (authors, R&D people, other professionals, quality volunteers, journalists, etc.) and organizations. We want to put information online for the general public pending a security review of the programming code.

Step 1 is fixing some bugs in what we already have, the PHP code. It is functional, and been used a long time, but there are some bugs.
Step 2 will be improving the system. Some small improvements would help its usability.
Step 3 will be a security check for putting it online for the general public to be able to access and use, but with reasonable protection against hackers.
After Step 3, the main mission is accomplished, as regards PHP / MySQL, though of course we hope to keep people engaged and happy, and the sky's not the limit.

This is a volunteer, unpaid role at this point in time. A limited paid role would be considered on a tight budget, such as for at least bug fixing with some minor improvements, and/or a security review of our code before it goes online publicly. If you or one of your friends or associates may be interested, please send an email to spaceprogrammer at ... of course this domain.

Reasons to do something yourself:

  • It will help save life on our special planet -- be part of the solution in your generation.
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  • It could be an interesting, cool, and a fun adventure for your life!

You can join us and volunteer to help out,

... or ...

If you're short on time, you can just donate:

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