Galileo IUS ignition Options

[nprev]

Wow. I and certainly others are edified & grateful; thanks very much, Jim & BP! The IUS has a much more varied history than I'd originally realized.

[Jim from NSF.com]

Forgot to add that DSCS-III flew on Shuttle with two spacecraft on an IUS. After Challenger, it was determined that it would be cheaper to launch the complete constellation of 10 satellites on an uprated Atlas Centaur (the yet to be designed Atlas IIA) with an yet to be designed apogee propulsion system (IABS). A person proposed this through the USAF Suggestion program. The suggestion was declined and then the gov't figured out eventually that is was a good idea and implemented it. The original suggester "protested" the response he got and was awarded 25K (the max amount).

There were backup plans to launch Galileo and Ulysses on T-IV IUS, in case the shuttle was delayed longer

[nprev]

Now that's a fascinating tidbit, Jim...thanks yet again! I made a couple of $s off of that suggestion program myself back in the day for airplane stuff, but nowhere near the max...good for him or her!

[edstrick]

The IUS was originally named the "Interim Upper Stage", when it was concieved as a short-on-budget stopgap that would be replaced by a combination of a true inter-orbit Space Tug ... planned as part of the Space Transportation *SYSTEM*.

When it became clear that "Interim" would last to the decay of the last proton in the universe, it was rather quietly renamed the "Inertial Upper Stage", meaning that it had 3 Axis inertial attitude control instead of spin stabilization, unlike most or all other solid fueled upper states.

This bogaceously expensive solid upper stage, with the miserable specific impulse of all solid propellant upper stages, cost as much or more than an equivalent performance Centaur upper stage, particularly when amortized over the enormous development cost of the stage.

In the end, it's only good feature was that as a solid fueled stage, it added minimal extra risk to Shuttle cargo missions that needed a big upper stage to deploy payloads to higher orbit.... an ability that was abandoned as fast as reasonably possible after Challenger.

[dvandorn]

When you consider that one of the next few flights of the Shuttle after Challenger was scheduled to be the launch of Galileo on a Centaur loaded into the Shuttle's cargo bay, it may not be completely correct that "interim" was a misnomer. There were plans, as of early 1986, to use the Centaur / Shuttle combination for a variety of large payloads, including planetary probes.

Of course, if you talk with Shuttle experts and afficionados, you'll hear the opinion that while Challenger was a tragedy, maybe it was a good thing in one way -- that the systems in place to fly an LO2-LH2 Centaur stage inside the cargo bay were so dangerous that we would have lost an orbiter trying to fly in that configuration. (Just the systems designed to allow fueling of and boil-off from the Centaur stage, IIRC, required major Shuttle safety waivers to be allowed to even be considered for a flight configuration.)

But it's good to remember that while the full "space tug" system was never going to be developed, there were plans to go beyond the PAM / IUS set of capabilities. And, therefore, "interim" wasn't necessarily going to be a completely dead concept. (Up until Challenger, of course, after which even the PAM / IUS configurations were considered too risky and phased out.)

-the other Doug

[Guest_Analyst_*]

I wonder if Jim has been the "original suggestor".

Analyst

[Jim from NSF.com]

I wonder if Jim has been the "original suggestor".

Analyst

Nope, I was an evaluator, but only on the shuttle parts of the suggestion

[Jim from NSF.com]

When you consider that one of the next few flights of the Shuttle after Challenger was scheduled to be the launch of Galileo on a Centaur loaded into the Shuttle's cargo bay, it may not be completely correct that "interim" was a misnomer. There were plans, as of early 1986, to use the Centaur / Shuttle combination for a variety of large payloads, including planetary probes.

Those plans were as earlier than 1983.

Just IUS and Centaur flew on T-IV, the IUS would have still flown for many more years. Some programs would not have migrated to Centaur

[Jim from NSF.com]

But it's good to remember that while the full "space tug" system was never going to be developed, there were plans to go beyond the PAM / IUS set of capabilities. And, therefore, "interim" wasn't necessarily going to be a completely dead concept. (Up until Challenger, of course, after which even the PAM / IUS configurations were considered too risky and phased out.)

The PAM/IUS was used for Ulysses

[BPCooper]

The PAM/IUS was used for Ulysses

And Magellan.

[Jim from NSF.com]

There was a smal difference, it was "bare" Star-48 motor, which means it didn't have any of the PAM systems, and it was part of the Magellan spacecraft vs the IUS.

[mchan]

There were also the 3-stage IUS configuration that were proposed for the split up Galileo orbiter and probe in 1984 after the 1982 launch opportunity with a 2-stage IUS was lost. IIRC, the 1984 proposal would have involved two shuttles launching within a week or two of each other, one with the orbiter, the other with the probe. Would have been an expensive set of launches.