Re: SL-16

Dr Paul J Henney (
Fri, 20 Aug 1999 11:17:28 +0100


Thanks for the clarification.
I think I meant to say CURRENT tumblers :-)


BTW I thought it was the venting of the excess propellent that produced the
tumbling or is it a combination of propellent and explosive bolts??

-----Original Message-----
From: Kurt Jonckheere <>
To: <>
Date: Friday, August 20, 1999 10:54 AM
Subject: RE : SL-16

>hello all,
>Paul J Henney wrote :
>>Other SL-16's have also been launched(zenit's) but are not known tumblers.
>SL-16 or Zenits are almost ALL known to be great bright easy-to-spot
>The first great Zenit flasher was 85- 97 B = 16182, several have
>These second stages are seperated from the active payload by
>explosive bolts.  They are usually flashing quite fast after
>lauch with less than one second.  Because they are about
>10 meters long, they become as bright as mag +2.
>Due to magnetic friction their rotation period slowly goes down,
>so the time between two flashes become greater.  For Zenits,
>it usually take about five months for the period to become
>about 3 times larger (in fact 2.71...=e times larger).  This time
>is known as the charateristic time of the rocket and depends
>(mainly) on the rocket itself, its inclination and semi-major axis.
>This means that after 2-3 years they become steady.
>You can find more about flashing satellites, theory
>and practice on the VSOHP :
>especially at the "flashing satellites" part.
>In the PPAS - BWGS part you can find a link to the
>PPAS database.  There you can check that SL-16s were
>nice tumblers.
>In our program of flashing satellites you can also notice some
>Zenits :
>96- 51 B b     24298/Zenit
>98- 43 G b     25400/ "Zenit" Resurs 1-x rocket
>98- 45 B b     25407/ "Zenit" C 2360 rocket
>99- 39 B b     NEW,  Okean-O Zenit, bright, fast flashing !
>96- 51 B is nearly Steady right now, the two launched in
>1998 have a period of 40 to 50 seconds.  Only the last one
>is still quite spectacular and will stay like that for two years
>or so !
>You can find the program overview at :
>(it will be updated next week or so)
>Please don't hesitate to send your timings (with date -time
>in UT - observer - ...) to
>Kurt Jonckheere (,
>observations collector for the Belgian Working Group Satellites.
>Get Your Private, Free Email at