Thanks Burns, I was completely forgetting the 480 million copper dipoles
(Westford Needles) launched into 3500-3800 km orbits. That's a lot of debris.
73 Trevor M5AKA
On Sunday, 6 July 2014, 14:03, Burns Fisher wrote:
Trevor, the link that Dan provided defines "orbital debris" as manmade. Thus I
suspect the millions count does not include anything naturally occurring. It
does seem to include flecks of paint and other material that come off a
spacecraft as a result of thermal stress or planned operations (I assume
explosive bolts and the like).
Dan, that is great info! Thanks from me too.
73,
Burns W2BFJ
On Sun, Jul 6, 2014 at 5:19 AM, M5AKA wrote:
Thanks for that Dan, can you just confirm that the millions of items of debris
that NASA was referring to are naturally occurring chunks of rock ?
>
>
>As you mention Weapons Testing in space has produced thousands of debris
>pieces in orbits around 800 km and below.
>
>73 Trevor M5AKA
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>On Sunday, 6 July 2014, 8:03, Daniel Schultz wrote:
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>>I noticed that after the last Dnepr launch, it's upper stage was raised
>>to an apogee of 1454 km, putting it in a 1454 km x 609 km orbit with a
>>97.9 degree inclination, in order to avoid collision with any of the 37
>>satellites it released.
>
>>There are, however, no legally binding requirements regarding debris
>mitigation.
>
>
>International agreement requires that objects in orbits lower than 2000 km
>must exit that region within 25 years after end of mission. Objects in orbits
>above 2000 km can remain there for longer than 25 years in a "disposal orbit",
>but only a few missions have the excess propulsion capacity to reach that
>orbit. Some US Government missions have disposed of upper stages to a higher
>orbit to avoid the need to issue a Notice to Airmen concerning the falling
>debris hazard. At least one polar orbiting weather satellite launch sent the
>upper stage on an Earth escape trajectory for disposal.
>
>It would seem that the Dnepr orbit is still too low to satisfy the
>international requirement.
>
>>In the case of amateur transponder satellites they can be assumed to have an
>>operation lifetime of 40+ years (think OSCAR-7), as I recall debris
>mitigation
>>suggests re-entry within 25 years of the end of mission. For amateur
>transponder
>>satellites this might imply 65 years in orbit.
>
>NASA is considering a revision to this policy to specify a total lifetime in
>LEO of no more than 30 years regardless of mission lifetime.
>
>Other interesting facts from Scott Hull's July 1 colloquium at NASA Goddard
>include:
>
>1. There are about 22,000 objects larger than 10 centimeters in the NORAD
>database, an estimated 500,000 objects between 1 and 10 centimeters which are
>too small to track, and millions of objects less than one centimeter. The
>Chinese Fengyun 1C disintegration in 2007 produced about 2850 trackable pieces
>of debris. The new S-band space fence will be capable of tracking objects
>larger than 5 centimeters when it becomes operational in 2018.
>
>2. There are about 4000 dead satellites on orbit, and about 1000 active
>satellites.
>
>3. The debris population has peaks at 750, 900 and 1400 km. You would have to
>go to Saturn to find a worse debris environment than that of a 750 km Low
>Earth Orbit. Science missions can be difficult when you live in a minefield.
>
>4. Most spacecraft disintegrations are caused by battery and pressure vessel
>explosions. Nickel hydrogen batteries are most susceptible to explosion but
>NiCd and lithium ion batteries can also explode. A lithium ion battery must
>NEVER be recharged after it has been fully drained. Rocket bodies left in GTO
>are subject to explosion when the perigee height dips low enough to begin
>atmospheric heating, which can cause remaining fuel in the tanks to explode.
>Modern mission design requires that batteries be disconnected from solar
>arrays and fully discharged and pressure tanks vented to space at the end of
>the satellite mission.
>
>5. Space is still pretty big. We have been lucky so far. Statistics predict
>another eight or nine major collisions in the next 40 years with just the
>current population of debris.
>
>6. The movie "Gravity" did have a science adviser, and they did get a few
>things right, namely that there were no loud sounds when the debris struck the
>shuttle, and objects with lower area to mass ratio arrived first. Nevertheless
>most NASA folks still consider the movie to be a comedy. If you have the DVD
>there is an additional 20 minute documentary video about orbital debris on the
>disk.
>
>For more information see http://orbitaldebris.jsc.nasa.gov/faqs.html#6
>
>73, Dan Schultz N8FGV
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