OT?: Goodbye to an era

Much as I hate to defend P-E the error was beyond all but a handful of the most advanced ATMs to detect. In fact hardly any ATMs are capable of making an R-C primary and they are so expensive for pros to make that comparatively few true R-C imaging systems are in amateur hands today even with the availability modern computer controlled polishers.

The SCT design is just so much easier to mass produce (and it is still beyond most ATMs) Meade and Celestron have that market.

Tests did show the gross error but were discounted as inaccurate (which they probably were) until the postmortem later showed they were right. Noone expected a gross systematic error of that magnitude.

They did test them to choose the best based on surface roughness. The P-E primary was the smoothest object ever manufactured.

You keep making this claim but there is no evidence for it. The project was in a budget overrun - everyone wanted to see it fly rather than being cancelled by penny pinchers (which was on the cards) so a few corners were cut.

It wasn't a cultural problem. They just did the wrong test. It would have been enough for P-E and Kodak to swap mirrors and retest to show that one of them *must* be wrong but they were overconfident about their novel null tester design.

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Dodging my questions i see, my whole original paragraph:

:As gov'ment programs go it worked pretty well for over 20 years, lots of :people productively employed over the years. Now compare the gub'ment :bailouts of the last 20 months and the liberal inspired housing bubble :and meltdown for a tab that is at least 10 times larger. Which do you :prefer? Do you vote that way?

How about answering the questions instead of expounding your bigotry?

All they had to do was point it at a star and try to focus it. They waited until it was in orbit to do that. As I understand it, Kodak actually tested their mirror. P&E didn't.

constraints.

Overconfidence can be blinding. Or defocussing, in this case.

Overconfidence, to the point of not checking your own work, isn't a cultural problem?

John

That isn't enough. The primary doesn't work without the hyperbolic secondary in exactly the right place. It would have to be a whole system test and would require a lot of extra engineering.

ISTR one was done with the mirror on its side but the effects of gravity made it less than useful.

These days they make a computational hologram as a completely different way of testing that is independent of the classic null tester. FYI the purpose of the null tester is to reduce the problem to the classic spherical mirror test that an amateur scope maker can do.

constraints.

Excessive spherical aberration in the final image.

The checks they did were supposed to be watertight. There was a systematic error in a test jig that went undetected.

It is easy with hindsight to pick fault but no one noticed it at the time. The irony is that with the launch delays they had ample time to have fully tested the subsystems and find the mirror fault pre launch. They were up against schedule and budgetary constraints to finish it.

Regards, Martin Brown

Whaddya mean, "was"? The Soyuz program is still operational. The most recent (TMA-18) was launched April 2nd and is currently docked on ISS. The next (TMA-19) is scheduled for launch on June 15th, with a further two later this year.

You have to remember that you are talking to an idiot that thinks that the ISS was/is meaningless. Some of us know better.

Tell us again how LCD displays did not come out until the 70s had passed.

Tell us about all the devices you had that used them in the 70s, asshole.

The Titanium cased, hugely expensive watch was the exception, not the rule.

The TI-30 came out in '78, the year I graduated and entered the service. The count of items that had them at that time was very few.

Now get off your little high horse, idiot.

John, I understand your pain. Believe it or not, I actually sorta agree with the Obama administration on what they (apparently) want to do with the space program. Do we need to put up a new weather satellite? Put it out to bid as commercial contract. Do we need to get some men to the moon? Fine, get LockMart or Boeing to do it at cost plus!

Now, I am a certified Space Nut, but I think that, with the shuttle, NASA became a government rat-hole instead of a space agency. Hence, its involvement and support for AGW...

Charlie

We've done comet and asteroid interceptions already. It might be helpful to assemble a vehicle in LEO, like at the ISS. If we had years of warning, which we could for most cases with enough telescopes, interception and deflection would be feasible. Slingshot trajectories might be needed in some cases.

A nuke would be effective with just a near flyby, without matching velocity vectors. Just get close and bang, ablate enough mass off the surface to give it a small kick.

The the ISS, and the dead astronauts, would arguably have a purpose.

John

I love technology. But I hate waste.

English translation, please?

To what end? Better fireworks in the sky when it comes down? What I'm bashing is terabuck-range expendatures and a dozen deaths with no goal or purpose. The ISS may as well be parked in a back lot at Universal Studios for all the science it's doing.

The "political brainwashing" here is selling a massively expensive and useless program to the public under false pretenses.

John

Weather satellites are useful, not to mention affordable. Men walking around on the moon are neither.

Mars acould be crawling with rovers and drills and chem labs for the cost of one Shuttle trip to that flying coffin up there.

The moons of the outer planets look mighty interesting. I wish we could afford to land robots on them.

John

The R-7 ICBM derived boosters have flown more than 1000 times (Sputnik, Vostok, Soyus) and quite a few early lunar, Mars, Venus probes, communication satellites an meteorological satellites. Apart from the early Sputniks, each launch carried several tons into orbit.

The US STS may have launched more tonnage to orbit, _if_ you consider the 100 ton orbiter as a useful payload for a particular mission :-).

However, if you consider as useful payload only the satellites and probes launched from the orbiter or modules launched to the ISS, the situation is quite different.

Why is a return from orbit capability needed ?

If you can not find people for a one way trip to space, do not send people to space !

In the atmosphere, launching a nuke will heat up the surrounding air. For each centigrade, the air volume will increase with about 1/273 so consider what happens, when the air is heated by thousands of degrees:-)

A nuke close to an asteroid is quite useless, unless the radiation from the blast will evaporate large amounts of materia form the object, causing a reaction in the opposite direction.

About 100 precisely placed, and sequentially fired SRB engines from the shuttle program.

You have to get them there, and set up the target location for all of them to thrust against. Then you have to place each one tip first at that location before locking its angle and firing it off.

I thought that was the game plan! A nuke detonated in vacuum still has a very large amount of energy to dispose of in a very short period of time, limited to radiation and kinetic energy in the mass that remains of the nuke. That should be good at close range for extremely quickly pimpling an asteroid with some sort of crater, and the mass vaporized from the crater will have as a whole a significant net linear momentum vector. Subtract that from the linear momentum vector that the asteroid just had, and the result is the linear momentum vector that the asteroid has after gaining a new crater. Vector values are quantified by both magnitude and direction. This means that if an asteroid is caused to erupt from its side the recently- vaporized contents of the new crater at high speed (remember, the eruption has mainly vacuum in its way), then the asteroid's course gets changed.

Changing an asteroid's course by thousands of miles out of hundreds of millions or billions of miles for it to travel does not sound that hard.

I wonder if all the rocket designers have ever considered that problem.

Ablate enough mass off the surface to give it a small kick? Brilliant idea.

John

It is like lightning not being able to be used for work due to duration and total net energy collected for use, and does not amount to s*it to perform the work of pushing the object away from the blast.

Long duration, hard, sustained push is what is needed. Rocketry answers that need, but it would have to be huge.

So put the nukes in a tube and anchor them (the tubes) against the planet THEN fire them off. That would do a better job of a directed push.

planet = spheroid = asteroid