Oh crap! You're right. What was I thinking. Momentary brain freeze.
This is exactly why good old Mr. George Roemer at Dulaney Senior High only let us use metric units. And he would as frequently say "kilogram meter per second squared" as "Newton" to ensure that we understand their equivalence. Hence, no momentary brain freeze just now. See what I mean?
I just discovered while checking this stuff at Wikipedia that there actually was (is?) an attempt to screw up SI in the exact same way that the English system is screwed up, by confusing mass with force and then introducing another unit of mass to "fix" it that's tied to the gravitational properties of the earth. This is the hyl or "metric slug" (neither of which I'd ever heard of before). It's 9.8 kg, the SI mass that accelerates at 1 m/s2 under a force of 1 kg-f.
I had heard of the pond and kilopond, though infrequently, as synonyms for 1 gram-force and 1 kilogram-force. But still...ah hem....
I don't have a problem with that since go is embedded in the units. By definition,
1 Newton = 1 kilogram X go 1 pound = 1 slug X go
No, that's just my point!
1 Newton = 1 kilogram x 1 m/sec2, or the force required to accelerate a mass of 1 kg by 1 m/sec2.
So the earth's acceleration of gravity, g0, can be given as approximately either 9.8 m/s2 or as 9.8 N/kg. (I would teach it both ways, as both have obvious physical meaning.) So g0 does not show up in SI unless you're actually discussing earth's gravity, or accelerations normalized to earth's gravity.
I think your second formula is incorrect also. 1 pound-force is the force that accelerates 1 slug of mass at a rate of 1 ft/sec2.
Well, thanks to my high school physics teacher (who was actually quite good) we never even learned what a 'slug' was. We did everything in SI and he'd take nothing else. This was in the early 1970s, and of course the United States would be completely metric/SI in just a few years so why bother learning obsolete stuff?
But the EES unit of mass is the slug, not the pound.
Correct, but who the hell knows what a 'slug' is?
I know now, but I sure didn't when I first encountered it. My high school physics teacher was a SI evangelist; I think that's where I get it from. So it was a shock to get to college and find the mechanical engineering professors (who weren't even American) did everything in traditional units. And what the hell was a 'slug', anyway? Rather than remember all the stupid constants that I'd frequently forget because I was accustomed to working in SI, I converted everything to SI, did the calculations and converted the answers back to traditional.
Saying "pounds-mass" is as wrong in rigorous engineering as it is to say "kilograms-force."
True, but done very often because even engineers have a better feeling for mass in pounds than in slugs.
In each system, in the appropriate computations, we use the constant g0 to refer to the conversion between mass and Earth gravity force units, where appropriate. This is the constant that allows us to use the same units for specific impulse whether we're working in EES or SI.
Yes, but it's offensive. Why should I have to introduce a physical property of the planet Earth into a calculation regarding the performance of a rocket engine that might even be in deep space somewhere?
The cheapness of Bob's solution is its reward. I highly doubt anyone wants to pay $32,000 for my refinement using best methods. Bob gave you a defensible answer for free.
Absolutely correct, of course, but far too subtle for the deniers. Besides the general innumeracy characteristic of pseudoscience of all kinds, the whole notion of a loose upper or lower bound based on a simplified model seems utterly alien to them.
They can't understand how anything but an exact model can possibly mean anything, nor do they accept the fact that we engineers do this sort of thing all the time. So often that we have an expression for it: a "back of the envelope" calculation.
Thrust is counteracting the gravitational force acting on the LM, that is, the LM's weight. Density is mass per unit volume. Weight and mass are not the same thing.
pounds = force grams = mass
Right. This constant confusion between pounds force and pounds mass is one of the many reasons I wish we could junk the traditional system of units once and for all and just use SI for everything.
You can minimize the confusion with traditional units by always stating "pounds-force" or "pounds-mass", but it's rarely done. Even rocket scientists screw up badly; the widespread notion of specific impulse measured in "seconds" is totally bogus because it results from an erroneous cancelling of pounds-force (of thrust) by pounds-mass (of propellant). In SI, the name number represents specific impulse in either m/sec or N-s/kg, both having far more intuitive meanings than "seconds".
With SI, entirely different unit names are used for mass (kilogram) and force (newton) so there's no chance for confusion. Except for those misguided souls who put "kilograms force" on torque wrenches...
The number-letter plan was adopted when it was thought there'd be shuttles flying from both coasts. Mission names would be of the firm STS-nc-A, where n was the last digit of the year in which the mission was originally supposed to fly, c was 1 for a KSC launch, 2 for a VAFB launch, and A was a serial letter within the year. So STS-51L, the ill fated Challenger flight, was originally supposed to launch from KSC in 1985 as the 12 mission of that year. It kept its designation when it slipped into 1986.
After Challenger the completed west coast launch site was mothballed as too dangerous, so NASA went back to the original numbering plan.
I really wonder...how many more Saturn IB's and V's could we have had for what the Shuttle cost us?
Oh man... there are so many I'm sure I'll miss some.
(That's the first time here I've ever combined bold and italic fonts.)
1. By "inner" and "outer" layers I assume he means those inside and outside the pressure bladder. I knew there were more layers than this, but I had to look them up.
2. The device marked "oxygen cylinder" is the sublimator.
3. The "backpack" is actually the OPS. (Okay, it's part of the backpack, but that wasn't an official term.)
4. The "radio" is one of the oxygen tanks in the OPS.
5. The helmet (and pressure bladder) kept the inside pressure a little lower than in the ship, about 3.75 psi vs 5 psi.
6. The "outer helmet" was not sealed.
7. Sunglasses pocket??
8. Radio switch? Uh, no, but at least it had something to do with the radio -- it was the communications connector
9. Oxygen in and out are reversed. Also, the right side is for the OPS, so the red connector should be the purge valve. The inlet should be blue. (The earlier A7L version is shown, but that's OK.)
(Those are the ones I spotted from memory. Now, checking the references...)
10. There actually is a sunglasses pocket there! Obviously not too much use on an EVA, though.
11. The tubing marked for cooling water is actually one of the vents taking air out of the suit. (The vents are on the medial side of each foot.)
12. The constant wear garment can be used with the suit, but normally the liquid cooling garment is instead worn directly next to the skin. I assume that's what the CMP does during his EVAs since the CSM doesn't provide liquid cooling, only air cooling. That was the original plan for the lunar EVAs too but their tasks were thought to be much more strenuous so they added the water cooling layer.
13. The EVA version of the suit had 14 layers, so he was close. From the inside out: rubber coated nylon pressure bladder, 5 layers aluminized Mylar thermal radiation barrier, 4 layers nonwoven Dacron thermal radiation spacer, 2 layers aluminized Kapton and beta marquisette as another thermal radiation barrier, Beta cloth (teflon coated fiberglass) for abrasion and fire protection, teflon cloth outer patches (where needed?)
It looks to me like the thermal barriers essentially formed a Thermos bottle, with the aluminized plastic layers forming the metallized radiation mirrors and the Dacron cloth layers taking the place of the vacuum gap in the bottle. The Dacron was in vacuum so there wouldn't be any internal convection, and since the aluminized plastic layers weren't rigid like the glass in a Thermos bottle the Dacron was needed to keep them from touching each other and conducting heat. The outer plastic layers were Kapton for its greater temperature range, the inner ones could be Mylar since they operated near body temperature.
I do wonder sometimes if anyone ever tried to shoot a bullet through a test sample of an Apollo suit to simulate a micrometeorite hit. It probably wouldn't stop a bullet, though, even if it did stop a much smaller particle.