[FPSPACE] Re 'first solar sail' -- Friedman is right

[Jim Oberg]

Re the debate about whether it's proper to call Cosmos-1 'the first solar sail spacecraft'....

http://www.nasawatch.com/archives/2005/06/earths_first_so.html
Friedman respons to Cowing: "JAXA conducted a deployment test on a suborbital flight -- and did not either build a solar sailing spacecraft or attempt to fly under sunlight pressure. Those latter two goals are unique (thus far) to The Planetary Society project. JAXA's test was a valuable milestone; the Society also had wanted to do a suborbital deployment test in 2001, but it failed when the Volna rocket payload separation failed. The JAXA deployment of a big thin film in space was not the first in space either -- the Russians actually did that twice in the 1990s deploying a large reflective sail in space from the Progress to be observed by Mir. The program was called Znaimye. Their sail also was not part of a solar sail spacecraft." 

Keith, I think Lou is correct in making this assessment. Cosmos-1 is the first known attempt to launch a vehicle designed to 'solar sail' in space, to the best of my knowledge. The Japanese experiment was a laudable mechanical engineering exercise but at an altitude that 'photon pressure' was hopelessly dominated by aero effects.  The two Russian reflectors were exactly that -- reflectors -- and not sails in any operational sense (and one failed to deploy properly anyhow), and all Russian commentary at the time discussed only illumination applications on Earth's surface, not spacecraft propulsion. It's also the Cosmos-1 explicit intention to perform controlled 'photon pressure' applications, which makes them different from the first space vehicle that actually experienced substantial 'solar sail' effects, Echo-1 back in 1960. So we can find bits and pieces of technology and physics in the past, which only makes Cosmos-1 a rightful and honorable heir to previous spaceflight, but also an innovative and potentially revolutionary FIRST.