Talk:Cosmos 1
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Physics of Cosmos 1
The statement: "With increasing distance from the Sun, fewer photons collide per unit time and acceleration decreases even further." is true, but does not apply to Cosmos 1. This only applies for a solar sail orbitting the Sun. Since the craft remains in earth orbit the distance to the Sun will not change significantly. Also, the acceleration due to sunlight is not constant for an Earth orbitting sail. The craft spends some part of each orbit in the shadow of the Earth, it spends part of each orbit moving toward the Sun (during this time the sail is tilted "edge on" to prevent sunlight from slowing the spacecraft) and only for a portion of the orbit does the sunlight increase the energy of the orbit. The accleration of the craft would then increase slightly each orbit but it would not be constant. --Mu301 14:33, 22 Jun 2005 (UTC)
For more information about the dynamics of the Cosmos 1 orbit see orbital motion (http://www.kiasystems.ru:8100/english/solarsail/navigation.html) calculations at KIA Systems. This is a design study from 2001 modeling the orbit changes for the Cosmos 1 mission. --Mu301 15:43, 22 Jun 2005 (UTC)
who is Wogman?
I've never heard of any Dr. Darren Wogman in connection with solar sails, and I do not believe that such a person was ever involved in the development of the solar sail technology - the concept, the Mylar, the Cosmos 1 spacecraft, or anything. Indeed Google only returns one functioning hit on "Darren Wogman" and none on "Wogman, Darren." Therefore, I've deleted the following from the story: "using the pioneering technology from Dr. Darren Wogman." Since Cosmos 1 is in the news, there are probably a lot of people visiting this article, so it's important that it be accurate. I'd rather err on the side of caution and just take out the Wogman reference. Is there anyone who would like to see it put back in? -Centurion328 10:26, 22 Jun 2005 (UTC)
It's a vanity page, created from a spree of vanadlism by user 217.207.114.119. --Madchester 15:00, 2005 Jun 22 (UTC)
launch date uncertain
The Cosmos 1 mission homepage (http://www.planetary.org/solarsail/) states:
The Cosmos 1 spacecraft will be shipped to the launch area in mid May. Until then we have put our countdown on hold. The actual launch date will be announced during the week of May 16.
Also, I made minor changes to the Cosmos 1 information in the solar sail article.
--Mu301 18:02, 7 May 2005 (UTC)
physics
"The craft would have been gradually accelerating during each orbit as a result of the radiation pressure of photons colliding with the sails."
- I thought it was from the solar wind.
- Aha. "Another false claim is that solar sails capture energy from the solar wind. The solar wind, composed of charged particles, would indeed apply a small amount of pressure to a solar sail, but this is small compared to the pressure exerted by light that would be reflected from the sail."
"Photons are the sub-atomic particles that make up light, and travel at the speed of light. As photons reflect off the surface of the sails, they transfer momentum to the object."
- How does this work, anyway? The photons would have to lose velocity if they transferred momentum, no? Are they absorbed and re-reflected with lower energy (frequency)? - Omegatron 18:07, Jun 22, 2005 (UTC)
- They are indeed reflected with lower frequency. The easiest way to think about it is to assume it's something similar to an elastic collision, but with the photon moving at C before and after impact. These assumptions are realistic under most conditions. --Christopher Thomas 19:28, 22 Jun 2005 (UTC)
- Careful! Even if the reflected photon had the same energy, a net momentum is imparted on the sail. As long as the photons are reflected from their original direction, the law of conservation of momentum will "enforce" this. Awolf002 19:57, 22 Jun 2005 (UTC)
- The change in momentum of the sail, however, results in a change in kinetic enery of the sail. This is balanced by a change in energy of the photon. It isn't always redshifted; for a decellerating sail, for instance, it would be blueshifted.--Christopher Thomas 20:05, 22 Jun 2005 (UTC)
- Well, read the Laser cooling article, where all photons have the same energy. You still change the momentum of the object interacting with those photons. Awolf002 20:13, 22 Jun 2005 (UTC)
- I am very familiar with laser cooling. The photons are absorbed and emitted at the transition frequency in the atom's rest frame. The frequency of the lasers is actually tuned to slightly below the transition frequency, with the extra energy for the low-to-high transition supplied by the atom's kinetic energy. From the lab's rest frame, it looks like the atom emitted a photon of higher energy than it absorbed. This is why laser cooling is effective.--Christopher Thomas 20:22, 22 Jun 2005 (UTC)
- Careful! Even if the reflected photon had the same energy, a net momentum is imparted on the sail. As long as the photons are reflected from their original direction, the law of conservation of momentum will "enforce" this. Awolf002 19:57, 22 Jun 2005 (UTC)
- They are indeed reflected with lower frequency. The easiest way to think about it is to assume it's something similar to an elastic collision, but with the photon moving at C before and after impact. These assumptions are realistic under most conditions. --Christopher Thomas 19:28, 22 Jun 2005 (UTC)
What's next?
Does anyone have information as to what's going to happen next, assuming that Cosmos 1 is lost? If it has crashed, what are the chances that the spacecraft will be salvageable? Did Moscow provide any guarantees and/or have any responsibilities wrt the successful launch? Will it require another $4 mil to finish and launch another spacecraft, or is Russian military going to refund any money because of the failure? --Itinerant1 20:23, 22 Jun 2005 (UTC)
- If the spacecraft failed to deploy, it's probably lost (capsule would have crashed into the ocean). If it deployed while in a low orbit, I'm not sure how much you'll get back in one piece (it's big and light enough that it _might_ not heat up too much on re-entry, but I wouldn't bet on it). Spacecraft launches are typically insured to cover the costs of a failed launch, so the Planetary Society will probably get back at least some of the money invested in the project. For official answers, though, check the Planetary Society's press releases and web page.--Christopher Thomas 20:28, 22 Jun 2005 (UTC)
- Really?? Whoa. Spacecraft insurance. - Omegatron 21:49, Jun 22, 2005 (UTC)
- The Cosmos team looks like they are downgrading the chance they think it might have survived. That's based off of the weblog linked to in the article, and the most recent set of Google News articles. Unfortunately, I haven't seen any mention of the it being an insured launch. (As litigation costs go up, fewer are these days.) It might be that on a limitted budget they didn't have enough money to pay for the insurance. Although you'd think they would after they lost the last one... (--68.111.76.49 (talk • contribs))
Why a submarine?
Why was it launched from a submarine? I've never heard of probes or satellites being launched that way. Are there advantages, if so, what? -- Tarquin 13:18, 23 Jun 2005 (UTC)
