Juno launching

Roamy here.  There might be a weather delay, but there’s a 70% chance that the Juno spacecraft will be launched at 11:34 AM Eastern time today.  The launcher is an Atlas V.

(click to embiggen)

An interesting fact about Juno is that it does not use a plutonium thermoelectric generator for power, as did previous missions to the outer planets.  Florida Today said:

Bruce Gagnon, coordinator of the Global Network Against Weapons & Nuclear Power in Space, has previously protested nuclear power’s use, noting, “It is quite interesting that NASA is going to use solar to travel to Jupiter — they once claimed it was impossible. I think it just goes to show you that they needlessly put people and the planet in grave danger during past plutonium launches.”

Those past plutonium launches they protested included the Galileo and Ulysses probes in 1989 and 1990.  There’s a lot of things that were impossible 22 years ago that aren’t now.  Solar cell efficiency has been steadily increasing, along with our understanding of radiation effects on new solar cell types such as triple junction.  Jupiter is 5.2 times farther away from the sun than the Earth, so it gets about 4% of our solar energy.  Jupiter also has radiation belts which make the engineering that much more challenging.  I took part in testing the solar cells used on Juno, understanding how much performance would be lost due to the radiation effects.  The science instruments on Juno have a tight power budget, but if they maintained contamination control, this is doable.

I’ll update this post with the launch video when it’s available.  Good luck and safe journey, Juno!

UPDATED and bumped: Launch was at 12:25 ET.
[youtube http://www.youtube.com/watch?v=jl77aJmuZtg&w=425&h=349]

4 thoughts on “Juno launching”

  1. A tight power budget and a mucking great “if” standing between success and adding another ball to the cosmic pinball machine. Is there a good reason for going solar on this mission, or was NASA just caving to hysterical idiots?

  2. Jeff, I’m just being conservative. They have planned for a 14% drop in power output due to radiation damage. The *planned* mission duration is one year at Jupiter, but of course, we’d like it to be longer than that. The Galileo spacecraft gathered science from Jupiter for nearly eight years, and I want Juno to be able to do the same.

    As for no-go on the plutonium, what the principal investigator said to Florida Today was, “No plutonium-powered generators were available when Juno design decisions were being made nearly a decade ago. An advanced nuclear generator was in development. But delays could have driven up project costs and pushed back launch.”

  3. Actually RTG technology was available and undoubtedly would have provided a far more dependable power source. But the enviromaniacs manage to scare the general population (and some NASA bureaucrats) every time RTGs are mentioned.

    I find it astonishing that in 1962 John Glenn, aboard Friendship 7, rode an Atlas vehicle to be the first American into orbit. Admittedly today’s Atlas is an all new generation of lift vehicles, but it is fascinating that the technology of half a century ago is still hard at work on the final frontier.

    Good work, Roamy. I’m glad that you, and your colleagues, are still doing your best to carry the fire.

  4. Thanks, Marine6.

    I was part of the team that looked at what if a Challenger-type disaster occurred with either Galileo or Ulysses on board. There was a lot of impact testing of the multiple containment design of composites and iridium, and also Monte Carlo computer simulations. Back then, solar cells just weren’t an option, and we tried to make the RTGs as safe as possible.

    The Atlas may yet carry humans into space again.

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