In light of the hoopla (well in space circles anyway) over the thirtieth anniversary of the Apollo-Soyuz Test Project (ASTP), Jim Oberg has a little corrective to point out the danger of confusing cause and effect:
Even if Apollo-Soyuz had never happened, Shuttle-Mir (in some form) would have become possible in the political context of the early 1990s, and both countries
Wednesday is the thirty-sixth anniversary of the first Apollo landing, and long-time readers will be aware that I and some others (primarily Bill Simon, also the Transterrestrial web designer) have come up with a Sedar-like ceremony to celebrate the event, and describe all (well, all right, not quite all) of the events throughout the history of the universe that culminated in it.
We’ll be discussing and perhaps reading from it on The Space Show tonight, from ten to eleven thirty PM, Eastern time (7-8:30 on the west coast). You can listen live on the Internet by following the link. It will also be podcast.
And if you want to perform the ceremony yourself, there are still a couple days to plan a dinner with some friends. It seems a little weird, but everyone I know who’s actually done it has been surprised and pleased with the results (we’ve found that people who aren’t as heavily into space actually find it more interesting than some of the more jaded types).
As I pulled into Titusville last week to the news that the launch had been scrubbed due to a sensor failure, I had similar thoughts to the following from George William Herbert, posted at sci.space.policy today, but he wrote them down, and I didn’t:
“Something has been nagging me since the current round of hydrogen depletion sensor problems started on Discovery’s launch attempt, and I haven’t seen any good comments come up on the newsgroups or other commentary, so I’m going to launch it out there.
The Shuttle design was intended to be highly reliable and to have multiple redundant sensors and systems in most key areas. By and large, other than structural items where it’s hard to have another whole heatshield under the first one, they have had good success with redundancy covering flight faults and avoiding nasty aborts and the like.
There is a key difference to be seen between the behaviour last week trying to launch Discovery, though, and what typically happens with say a large 747 jetliner and its typical operational cycle.
Airliners have what’s called a Minimum Equipment List. This covers a set of systems that have to be operational in order for the vehicle to safely depart on a flight. The MEL is usually designed so that a number of minor faults are tolerated, and in areas where a fault would cause the aircraft to have to stay and be repaired, where possible an extra set of redundancy is applied so that if four units are needed for safe suitably redundant flight operation, five are installed, and the MEL is four. One sensor or navigation system or whatever can be completely broken, and the required flight safety level is still met with the remaining units.
Airliners are designed that way because it costs serious money when they can’t depart on time… either they have to be repaired in a hurry, which means lots of technicians at each airport and lots of expensive spare parts stocked everywhere (plus, a long enough operating cycle to accomplish the repairs in), or you have to scramble to find another plane to shift to the flight whose aircraft is down with a gripe, and then shift another plane to cover for the one you grabbed, and so on.
Shuttle was designed with an adequate level of systems redundancy for safety considerations, in most systems. It was not designed with an adequate level of systems redundancy for operational considerations. The cost per day of a Shuttle sitting on the pad, the ops crews and the control room crews and the costs of a rollback and destacking are all very significant. The opportunity cost of not being able to fly on time is also not at all a minor issue, with Shuttle’s life span limited by a currently hard deadline and too many ISS flights remaining to get done between now and then.
Redundancy is often described in “N+1” or “N+2” or “2N” terms; shorthand for one or two more units than are required for safe operation, or twice as many as are required. MEL logic really goes to a different level. We should really be looking to “(N+1)+1″, or both safety redundancy and an operational redundancy margin. Defining the safety redunancy factor as the N plus or multiplied by whatever, we can then define an operational redundancy factor, consisting of some margin on top of the minimum safety requirements. In shorthand, let’s say O for Operational Factor = (required safety factor including margins), or for example O = N+1 . The operability factor would then be, for example, O+1 or 0+2, with the additional operability margin depending on the maintainability of the parts.
Future reusable spacecraft and their operators generally already have a clue about these issues, but it bears repeating in public to make the point. The capsules I am working on should not have to be destacked and dissassembled if one out of a set of four units fails while we’re on the pad; either there should be a fifth, or three should be adequate for safe flight including safety margins, and listed in the MEL. The same should go for any other manned orbital project.
Not every system can be made this redundant, but as Discovery is showing, there are many systems for which safety dictated enough redundancy that adding an operability margin on top of that would have not been that difficult. Two wires in the shuttle/tank interface, one more sensor unit, a few pounds of payload capacity lost… and how many millions of dollars lost destacking Discovery the first time, and in this launch delay now?
Thin margins kill costs.”
[Copyright 2005, by George William Herbert]
[Update a few minute later]
Via Clark Lindsey, here’s a good description of the sensor that failed from Bill Harwood.
I should also mention that there’s a good discussion of the problems associated with troubleshooting this problem over at sci.space.policy. Some of the posters there are theorizing that it’s a separation of an electrical conductor that only occurs at cryo temperatures (if so, it would likely be due to differential thermal expansion). They also point out the high costs of figuring out just where it’s happening to the degree necessary to have confidence in flying again. And as always, it points out the fragility of the system, and the danger of relying on a single hardware concept for all of NASA’s human exploration goals. Because this is an element of the external tank, which would be common to all Shuttle-derived heavy lifters, our ability to get to the Moon would be shut down until this issue was resolved.
There are many lessons to be drawn from the programmatic disaster that is the Shuttle program. Unfortunately, many of the most popular ones are wrong. Alan Boyle has apparently succumbed to one of them, when he writes:
Of course, it takes a lot of innovation to replace a manned spaceship capable of putting almost 30,000 pounds of cargo into orbit. I
We heard about the launch scrub just as we were pulling into Titusville. We headed back down the coast, but took A1A all the way, so it was a longer, but more scenic trip.
I find it a little ironic that the part that failed today was one of the components that Mike wants to keep ad infinitum, while there was no problem with the Orbiter, which he wants to retire. I may have some further thoughts on this at TechCentralStation, if I can work up the gumption for a piece, but unfortunately, because I lost any productivity today to this futile expedition, I’ve got three other deadlines breathing down my neck in the next couple days.
I just got a call from Bill Khourie (pronounced ‘curry’), Director of OSIDA who let me know that they are putting their finishing touches on Oklahoma’s spaceport application with FAA AST and environmental impact statement and are targetting December 2005 for approval for horizontal takeoff horizontal landing vehicles. He said they would be delighted to be approached by the vertical crowd and would be pleased to welcome them assuming AST says OK.
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Wednesday, 15:30 CDT: One of the vertical crowd emailed me and said that they already approached OSIDA some time ago and “would be pleased” might not be enough to get a new AST spaceport application filed.
Over at The Space Review today, Jeff Foust has a more detailed critique of the “Abbey-Lane” Report, a document that I didn’t have a very high opinion of. Also, Craig Carberry has a rundown of the political prospects for NASA and the Vision for Space Exploration in the context of the 2008 elections. He repeats a popular myth, though–a common one:
…it was a Republican president who initiated the new vision, and back in 2000, the Republican platform called for
I got this message from Ned Abel Smith of Virgin Galactic this morning.
Hope all is well. Only 2 of us made it into the office this morning due to the Suicide attacks on London, but have heard that everyone is accounted for. Very scary.
He also answered my question about where deposit money goes:
All moneys are not kept in escrow and therefore any deposit received is backed by Virgin Holdings Ltd.
This project is so exciting because its so real and anyone that has the opportunity to become a Founder or Pioneer with us is incredibly fortunate. I have attached your Terms and Conditions to be printed and signed.
Here are the terms and conditions Ned mentioned:
Mike Griffin has been calling for using nuclear power for Earth’s rocky Moon exploration rather than Jupiter’s Icy Moon exploration. Anti-nuclear activists should propose a cost-effective non-nuclear alternative.
Here’s an old idea for lunar nighttime power worthy of rediscovery: laser illumination of solar cells from Earth.
Mike Griffin has been calling for using nuclear power for Earth’s rocky Moon exploration rather than Jupiter’s Icy Moon exploration. Anti-nuclear activists should propose a cost-effective non-nuclear alternative.
Here’s an old idea for lunar nighttime power worthy of rediscovery: laser illumination of solar cells from Earth.