AO-51: SK. It was fun...

[Moleculo]

AMSAT has announced the end of mission for AO-51. What a great bird and congrats to the AO-51 team who brought a lot of fun to ham radio. It will be missed.

AMSAT - AO-51 Control Team News

 

[K4WOW]

Tis a shame

Just having gotten started on FM sats, I never had a chance to work AO-51. Heard it a couple of times during my learning/listening phase before it petered out.

Now we have AO-27 which rocks and SO-50 which is a real challenge for me handheld.

I missed out on 7 years? Bummer!

 

[Captain Kilowatt]

With AO-27 having spent 18 years in orbit as of this past September and SO-50 approaching nine years it makes you wonder just how much life those two easy-sats may have left in them.

 

[office888]

We need an RTG powered AMSAT.

 

[Captain Kilowatt]

We need an RTG powered AMSAT.

I don't even want to think about the effects of a launch failure with a RTG on board. They work well but the risks of a failure are too high IMHO especially for an AMSAT.

 

[office888]

I don't even want to think about the effects of a launch failure with a RTG on board. They work well but the risks of a failure are too high IMHO especially for an AMSAT.

It has happened before in the far past. And nothing happened to the RTG.

Voyager 1 is a true story of success though! It finally is at the edge of interstellar space...and still transmitting data back at about 115 kilobit/s. It will continue doing so until about 2025.

Not bad, considering it was launched in 1977.

 

[Captain Kilowatt]

There is always a risk of containment failure over populated areas. The known failures have been over water mostly either by design or luck. Either way it's a pretty expensive option for a ham sat.

There have been at least six known accidents involving RTG-powered spacecraft:

1. The first one was a launch failure on 21 April 1964 in which the U.S. Transit-5BN-3 navigation satellite failed to achieve orbit and burnt up on re-entry north of Madagascar.[16][17] The 17,000 Ci (630 TBq) plutonium metal fuel in its SNAP-9a RTG was injected into the atmosphere over the Southern Hemisphere where it burnt up, and traces of plutonium 238 were detected in the area a few months later.
2. The second was the Nimbus B-1 weather satellite whose launch vehicle was deliberately destroyed shortly after launch on 21 May 1968 because of erratic trajectory. Launched from the Vandenberg Air Force Base, its SNAP-19 RTG containing relatively inert plutonium dioxide was recovered intact from the seabed in the Santa Barbara Channel five months later and no environmental contamination was detected.[18]
3. Two more were failures of Soviet Cosmos missions containing RTG-powered lunar rovers in 1969, both of which released radioactivity as they burned up.
4. There were also five failures involving Soviet or Russian spacecraft which were carrying nuclear reactors rather than RTGs between 1973 and 1993 (see RORSAT).[19]
   A SNAP-27 RTG deployed by the astronauts of Apollo 14 identical to the one lost in the reentry of Apollo 13
   
   
5. The failure of the Apollo 13 mission in April 1970 meant that the Lunar Module reentered the atmosphere carrying an RTG and burnt up over Fiji. It carried a SNAP-27 RTG containing 44,500 curies (1,650 TBq) of plutonium dioxide which survived reentry into the Earth's atmosphere intact, as it was designed to do, the trajectory being arranged so that it would plunge into 6–9 kilometers of water in the Tonga trench in the Pacific Ocean. The absence of plutonium 238 contamination in atmospheric and seawater sampling confirmed the assumption that the cask is intact on the seabed. The cask is expected to contain the fuel for at least 10 half-lives (i.e. 870 years). The US Department of Energy has conducted seawater tests and determined that the graphite casing, which was designed to withstand reentry, is stable and no release of plutonium should occur. Subsequent investigations have found no increase in the natural background radiation in the area. The Apollo 13 accident represents an extreme scenario because of the high re-entry velocities of the craft returning from cislunar space. This accident has served to validate the design of later-generation RTGs as highly safe.