OT: Random question for the physics guys

Re-watching some of this series with the SO and, cuz I'm a nerd the question occurred to me: Is an object falling through the lower atmosphere at terminal velocity as massive as the Galactica creating enough heat from friction/ram pressure to be shooting flames all over the place as in the following clip?

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Reply to
bitrex
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When the ship jumps away and leaves a big vacuum behind, I thought all the rocks and dirt being sucked up into it was a nice touch of "realism", at least.

Reply to
bitrex

Probably not. Only because the design would have used something like the ceramic tiles on the space shuttle. So you would get incandescent surfaces ,but not flames. But if there were anything that could burn, then there would be flames.

Dan

Reply to
dcaster

On Aug 14, 2016, snipped-for-privacy@krl.org wrote (in article):

More to the point, if it were moving as slowly as shown (or even for the human eye to be able to track), there would be no flames or incandescent glow at all.

Also, launching that one-man fighter sideways from the mothership while at reentry speed would break the fighter in half as it left the launch port.

Joe Gwinn

Reply to
Joseph Gwinn

Even Mercury capsules caused enough air ionization to blank out radio communication during re-entry. Shuttle re-entries were easily visible from the ground, and that wasn't radiation from the tiles.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

ceramic tiles on the space shuttle. So you would get incandescent surface s ,but not flames. But if there were anything that could burn, then there would be flames.

I seem to remember someone working on a heat shield from something similar to cork that was actually supposed to slowly burn away

-Lasse

Reply to
Lasse Langwadt Christensen

Not bad for a short scene. I might just rewatch the series. Was a fan of farscape at the time too. Too bad the sifi channel isn't much syfi anymore.

Cheers

Reply to
Martin Riddle

The difference here (assuming for the moment that this fantasy situation were realistically possible) is that our steely-eyed captain has somehow rapidly brought his battleship to something like 0 relative velocity with the "target" while still in orbit, and then

Reply to
bitrex

Oops. And then "dropped the ship like a rock" from some altitude above the atmosphere, say 100 miles, and just let Newton do the work in the Z direction.

I'm sure it would take an enormous amount of energy to get a spacecraft with a mass of ~a million tons to do all these maneuvers, but as they appear to have some fashion of magic engine available with enough power output to bend spacetime, that what's needed is on tap..

Reply to
bitrex

All of the re-entry vehicles, other than the shuttle, use(d) ablating heat shields.

Reply to
krw

org:

r

the ceramic tiles on the space shuttle. So you would get incandescent surf aces ,but not flames. But if there were anything that could burn, then the re would be flames.

ar

I guess that wasn't expensive and complicated enough for the shuttle ;)

-Lasse

Reply to
Lasse Langwadt Christensen

I read somewhere that the fictional Galactica is about 1 km long. So assuming a cross sectional area of 300,000 square meters, a mass of maybe 10 million tons, ten times that of an ULCC tanker, and a drag coefficient of 1.5 (a few tenths less than a flat plate oriented towards the flow) the calculator I'm using gives a terminal velocity of nearly Mach 2. :-)

Reply to
bitrex

All, what's known as "Science Fiction", today, (and most other genres, including chick flicks ;-) require a suspension of disbelief. Why should this be any different.

Reply to
krw

Ablating heat shields are pretty hard to reuse. ;-)

Reply to
krw

Naturally. But IMO the best sci-fi only requires only a couple leaps of disbelief, and the rest of it tries to operate within some kind of constraints still imposed by the physical universe, with some kind of consistency.

That is to say, the author might say "Okay, there's warp travel, and whatever associated technologies are required to build spacecraft that can endure it. But people still need to eat and shit and take out the garbage and all the other tasks of daily living required by the physical universe."

That's why I'm not a big fan of Star Trek. They have so much fantastic technology - warp drive, transporters, holodecks, food replicators, alternate the shield frequencies, etc. that it's essentially magic, and you constantly end up with suspension of disbelief shoved in your face to the point that it becomes distracting.

Why does everyone take the elevator everywhere on the Enterprise, when they have matter teleportation and essentially unlimited energy on tap? Why not just teleport from the bridge to the bathroom? Why do they even have to fight the baddies at all? With that much technology they should be able to just wave their hands and make them disappear.

Star Trek isn't really "science fiction" as I'd define it. It's definitely more like "space opera"...wizards and dragons and magic, but set in space.

Reply to
bitrex

The ship in Star Trek: Voyager spend ~7 years lost in the galaxy trying to get home and at the end of the series the paint wasn't even scratched!

What I liked about the re-imagined Galactica is that after several years of doing the same thing, the Galactica is absolutely wrecked and beat to pieces. Like it actually existed in the real universe...

Reply to
bitrex

Den mandag den 15. august 2016 kl. 00.01.23 UTC+2 skrev krw:

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ke the ceramic tiles on the space shuttle. So you would get incandescent s urfaces ,but not flames. But if there were anything that could burn, then there would be flames.

milar

sure but sometime replacing a single use consumable is the smart and cheap choice ;)

-Lasse

Reply to
Lasse Langwadt Christensen

Would it have even been possible to design an ablative heat shield that was relatively straightforward to replace, yet could still protect all those aerodynamic surfaces well enough, using circa 1972 technology?

I seem to remember that the engineers toyed with the idea, but discarded it.

The fact is that the Shuttle wouldn't even have needed all those aerodynamic lifting surfaces if not for the ~1000 km crossrange requirement imposed by the military. It wasn't completely NASA's fault the system was expensive and complicated; it could've been simpler if the DOD didn't have its heart set on a system that could be launched from Vandenberg northbound on short notice and do a 1 orbit return to launch site.

Reply to
bitrex

If you have the technology to warp space, what's the big deal with your maneuvers, above? Energy isn't an issue, at that point.

But then there was "A Piece of the Action". Of course none of these "science fiction" movies has anything to do with science. They're just another cowboy shoot-em-up: white hats and black hats. I have no problem with that, either.

Because the teleporter never works when they need it.

I bet your head explodes when you realize their elevators don't just operate in one dimension. ;-)

Wild West = Wild sector 4. What's your problem?

Reply to
krw

I thought the three letters were missing.

That was the big thing with Star Wars. Everything was really grungy (except the imperial storm trooper's helmets, I suppose). Again, it was nothing but a pirate movie. It's called "entertainment". It's hard to be entertained if you try to analyze everything. Science fiction isn't alone, in this respect.

Reply to
krw

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