Thank you Sil - excellent explanation.
Jeff
----- Original Message ----- From: "Sil - ZL2CIA" zl2cia@amsat.org To: "jkelly@home" jkelly@bellatlantic.net; "AMSAT" amsat-bb@amsat.org Sent: Saturday, December 15, 2007 6:04 PM Subject: Re: [amsat-bb] Explain Photo?
jkelly@home wrote:
Can someone explain to me what actually is happening in this photo?
http://www.eanet.com/kodama/astro/2007/1110a/7.htm
Jeff KT2K
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Hi Jeff,
you probably want to know more than this..
What I understand is happening is that the excess fuel (propellant and oxidizer) is vented from the rocket. This is fuel that was unused by the rocket and remained in the tanks. The rocket motor was shut down before all the fuel was used because the rocket had reached a sufficient velocity to attain the required orbit.
I think the fuel is dumped into space because it is considered a safety risk to leave it in the rocket's fuel tanks.
When the fuel is dumped, it does not burn. The fuel is visible because it reflects sunlight before it becomes dispersed. I imagine that the fuel is released in liquid form. Surface tension probably forms it into small droplets which quickly evaporate.
While it looks as though the fuel is being squirted out of the rocket in a jet of fluid, it is not and this is an illusion. The fuel is vented and the cloud of fuel immediately starts expanding into the vacuum around the craft. In this photo, the rocket is moving from left to right. It is orbiting and not being propelled by it's motor any more. The fuel on the left of the picture has had more time to expand into space, while the fuel on the right has only just been released. This creates a nice illusion of a jet from the rocket but that is not what is happening in this photo.
There must be more to the story that this. Even dumping the fuel could alter the orbit of the craft, so it would have to be done in a very managed way. I have read that the Apollo 13 flight suffered an error because the Lunar Module (used as a lifeboat) vented waste gases unevenly.
It you are interested, I found a story about another space fuel dump here:
www.space.com/spacewatch/mystery_cloud_040901.html
And a story about some on watching it here:
http://www.satobs.org/seesat/Nov-1997/0141.html
And here:
http://www.allaboutastro.com/Delta4.html
It would be a cool thing to see.
Best wishes.
Sil ZL2CIA