2014-01-07

Quick Review: Mythbusters AT-ST Log Smash

So, did the Mythbusters get it right?

In broad strokes, yes.  As reader Vorus noted, my old 2002 page on the AT-ST log smash held up well compared to their scrutiny.

In short, they build a rig with telephone poles and hang logs beneath them, pulling them back and letting them smash a test vehicle and then a full-on (and nicely painted) armored truck of the sort you might expect to haul bank loot.

There were some great moments beyond the eminently television-friendly Kari's various attire, such as Grant Imahara describing "back of the envelope" calculations suggesting that the energy involved per log was going to be about a megajoule, followed by a quick flash of assorted scenes from the show of megajoule scale, like car crashes and so on.

The total for both logs of two megajoules falls in line nicely with the notations on my AT-ST log smash analysis page in which, as always, I heap the benefit of the doubt upon Star Wars and basically double the likely figures.   The Mythbusters team, unencumbered by claims of bias from a group of Star Wars fans bent on maximizing Star Wars technology at every turn, felt perfectly at liberty to simply follow the facts and not inflate the figures in favor of Star Wars.

But, there were also some oddities.

"Aren't you a little short for a chicken walker?" - The AT-ST height is given as 20 feet (a rather low figure given that the full-scale mock-up in the film was over 8 meters, or 26 feet), and for some reason they felt it necessary to then hang a Ford Econoline test vehicle at that height for smashification.   Not only was the altitude completely unnecessary, but it put undue stresses on their rig to move the logs about at that height.   Fortunately this was abandoned for final testing, otherwise they would've had to rebuild it. 

"Aren't you a little short for an Ewok log?" - Also, despite having a fake log of proper length to width ratio at the beginning of the episode, it is somehow decided that the logs in the film are about ten feet long and five feet wide, which makes them entirely too short.  In the scene below, for instance, the logs would not even extend all the way to the edge of the frame.



On my page I came out with 1.5 meters by nine meters, or about five feet in diameter and 30 feet long.  And, since their targets were quite a bit shorter than the AT-ST cab section, the five foot logs looked a bit monstrous.

"Aren't you a little short for a log nose?" - The logs themselves were unfinished, in the sense that they were straight or nearly-straight cuts and had no pointed/rounded tips.  In the first hit against the armored truck, this seemingly resulted in the left side (as viewed from the front) not actually penetrating the side of the vehicle since it hit the roofline broadside.

"Aren't you a little far back for a logsmash?" - The first strikes were against the flat sides of a van and then the flat side of an armored truck.   In the case of the truck the right side simply caved in, which makes sense given that there is likely very little actual vehicle structure back there.   The second hit, however, was aimed more forward, and literally tore the roof off of the vehicle and smashed the cabin.  There is likely a pillar just behind the driver's door, making that more of a fair test.   After all, armored trucks of that nature are mostly intended to be bulletproof rather than structurally strong.

Of course, comparing that to the actual AT-ST's structural failure is interesting, since the first hit, as noted, only poked a hole in the truck.  The general structure appeared to remain fairly intact.   Compare that to the logsmash itself, in which the AT-ST literally crumples.   I guess in an age of blasters, the notion of kinetic impact may seem altogether quite foreign.



"Aren't you a little hard for a log?   Wait, don't answer that."  - For some unexplained reason, eucalyptus logs were selected explicitly for their hardness.   Presumably this was intended to allow repeated strikes without fear of log failure . . . the rig, after all, would've been rather difficult to 'reload'.    Nevertheless, it seemed odd when watching initially.

This does bring me back to my page, however.   I did assorted calculation via forces and whatnot, but never really got into the actual pondering of hardness of the AT-ST hull.   Given the malleability against logs it would be nice to review that ancient page and see what I can come up with in that regard.   Presumably I dismissed it back then as relatively unimportant, given that I had already concluded that AT-STs were more or less bulletproof.

In any case, I'd say the Mythbusters team did a great and very entertaining job, and it was great fun to see things get smashed and have Grant Imahara generally confirm my old figures.

2014-01-05

Shuttlecraft Terminal Velocity

Number-crunchy-stuff, ahoy!

Perusing a page on my site, I saw where I'd said I wasn't sure what the terminal velocity of a Federation shuttlecraft might be.

Well, *that* needs fixing, so we're fixing to fix that right now.

Applying Google-fu, I found:  http://www.wikihow.com/Calculate-Terminal-Velocity .  There, we are told that terminal velocity is the square root of the following:  2 times the mass and times gravitational acceleration, divided by the density (of air) times the area of the object times the drag coefficient.

Easy enough, with caveats.

First, we have a mass of the Type-6 shuttle that is an estimate from my Volumetrics pages, scaled down from the density of full-size ships.  That said, the Delta Flyer is believed to be of similar density to Voyager, and so we're gonna roll with a similar density, providing a mass of 29 tonnes . . . that's only about half the mass of an M1A1 Abrams tank, so I'm cool with it.

Second, the reason I didn't think I'd be able to calculate it before is because I had no method of determining the drag coefficient.   However, I am now willing to make scientific-sounding wild-ass guesses.   For instance, a handy-dandy list of various drag coefficients is linked to from the WikiHow page.  For example, a cube is said to have a drag coefficient of 0.8, a flat square plate facing the wind provides 1.17.   For our purposes, we'll want to look at something akin to a minivan or SUV and then bump it up a notch to factor in the nacelles.   Doing so, we find that an SUV commonly falls somewhere in the neighborhood of 0.45 or less, while a bus is listed as 0.6 to 0.8.  So, I'm going to say a shuttlecraft should be in the 0.55 range, but your coefficients may vary.

A final problem is finding the frontal area of the shuttlecraft . . . as in, were it to fly through paper and cut it perfectly rather than tear it, thus making a neat shuttle-sized hole, what would the area of that hole be?  Fortunately, this is easy enough with Google Trimble SketchUp, at which point we find a frontal area of 7.55 square meters, give or take.



So, now we have basically all the parts we need.   For the density of the air we will just rough it as an average of .9 kg/m^3 . . . at sea level it can be 1.2, but at 50,000ft (15km) you're gonna be looking at a much lower value, somewhere in the .3 range.   .9 is the pressure at about 7500 feet (~2300m).

The terminal velocity of a shuttlecraft is thus the square root of:   2 times 29,000kg times 9.8 m/s^2, divided by 0.9 kg/m^3 times 7.55 m^2 times 0.55.

Check my math, but I believe that works out to the square root of 568400/3.73725, or the square root of about 152090, which yields about 390 m/s as the terminal velocity.  

Interestingly enough, that's greater than Mach 1 at the altitude indicated by our "average" pressure.   If we calculate instead based on sea level pressure of 1.2 kg/m^3, then the terminal velocity drops to 338 m/s, which is so close to Mach 1 at sea level STP (340 m/s) that, given the back-of-the-envelope wild-ass nature of our exploration, it might as well be close enough.   (And hey, wouldn't it be cool to see the transsonic condensation clouds around a shuttle as it is about to hit the ground?)

So, terminal velocity of a shuttlecraft is approximately 340 m/s (Mach 1) at sea level, and greater than Mach 1 at higher altitudes.

Now, of course, it's worth noting that this is not especially useful for the page in question, since the shuttle from "Rise"[VOY3] was not actually dropping like a brick, but was instead engaged in powered descending flight and then suddenly lost power.  The result would be more like a ballistic trajectory than a simple fall.   But hey, it was fun anyway, wasn't it?

2013-12-29

Did the Enterprise See Herself?

While writing on a page, a thought crossed my mind.

You see, it seems very odd that the Federation would have authorized the intentional time travel mission from "Assignment: Earth".   Even if you assume that the timeline is pretty robust and resilient, it doesn't seem wise to plop an entire bright-white 289 meter Constitution Class starship in 1968 Earth orbit when the same job could be achieved by a specialized low-observability vessel or microsatellite or somesuch.

However, it also occurs to me that "Tomorrow is Yesterday" did feature an accidental dropping of the same Constitution Class starship into Earth's atmosphere.   On that occasion the Enterprise escaped via some sort of unusually slow time-warp maneuver.  Her sensors were capable of recording information at the time, which is how they were able to do the beaming maneuver as they slowly returned to their time.

So, as they travelled forward in time with sensors recording information, did the Enterprise see herself in 1968, which led Starfleet's eggheads who were later poring through the sensor logs to send them back there?   Was her assignment to 1968 Earth thus a predestination paradox?

Just a random thought.

2013-12-28

Ben Sisko, Gunslinger

Imagine if you are sent back in time by accident.

You awake in a strange land of oddly dressed humans . . . they speak English but it sounds quite odd to your ears.  Seeing your strange clothing they assume you are some sort of spy for their foes and detain you, along with some others.

You soon come to realize that you are in the colony town of Lexington, Massachusetts in mid-April 1775.   You manage to escape, but in so doing you inadvertently cause the death of Solomon Brown, who (we shall pretend for the purpose of this gedankenexperiment) fired the first shot against the British redcoats from the area of a tavern on April 19, 1775.   Aware that your action has potentially screwed with history, and knowing you have only minutes to make history right, you take on his identity, picking up a weapon of the era and firing the shot at the appointed time.

Okay, so this is all well and good, but there's a problem.  Unless you are especially well studied in the arms of the era and not just the historical specifics, you really ought not have much idea of what to do with that weapon.

Sure, just from watching the History Channel or somesuch, you'd know that you're probably dealing with a muzzle-loading weapon, hopefully with a rifled barrel.   You'd probably try putting some powder down the barrel, maybe a piece of fabric or paper or somesuch, then a ball.  You'd tamp it down and then try to figure out how to deal with actually firing it.   Is there something to light which then makes contact?   Is there a flint striker?   Do you need to put a little powder down some other hole?  

You may have been hanging out in the 1770s for a day or two and seen other weapons, but unless you've had a chance to observe them used you may have no idea how to actually make the gun go boom.   And if you fail, the American Revolution may happen completely differently.

This brings us to 2024.

In "Past Tense", Ben Sisko is thrown back in time from the 24th Century.   Placed in a concentration camp for the poor, his knowledge of the era's history leads him to realize that he is at the precise location which, in mere days, will be the epicenter of the Bell Riots, a watershed event of the 21st Century.  While trying to survive, an event occurs which causes the death of Gabriel Bell, hero of the event.   Later, as the riots break out, Sisko grabs a shotgun, immediately racks and fires it, and is then able to take control of the situation along with Gabriel Bell's identity.   His action gets him shot later, but keeps history correct.

The problem with that story is pretty much identical, except in his case a Remington 870 is dropped into his hands and boom, he's running the thing smoothly.

While I'm hardly a firearms expert by any stretch, I have owned, handled, and fired a variety of pistols and rifles.  I am at least basically familiar with the operation of such weapons from .22 revolvers to 1911-style semi-automatic pistols to bolt-action magazine-fed rifles to semi-automatic "assault" rifles.  I even shot a friend's 12 gauge shotgun a few times over ten years ago, though as I recall he probably did the loading.   I was also recently helping a friend who was having issues with his 12-gauge semi-automatic shotgun, aiding in the disassembly and helping assess what was going wrong with it on the trigger group mechanically, and even watching him fire it.

But when roaming around in a sporting goods store a few months ago, I spotted a particularly interesting pump-action shotgun and asked to take a look at it.  The kid behind the counter handed it over and I was giving it a look-see.  I had the mind to rack it, pulled back on the fore-end and  . . .  nothing happened.  It wiggled but didn't otherwise budge.  Trying to look nonchalant, I fiddled with the safety and messed around otherwise, surreptitiously trying to rack it again, to no avail.  As I had no real interest in purchasing the shotgun I didn't just decide to stop and ask for directions from the kid as I normally would be happy to do when lost . . . I simply handed it back and thanked him.

The thing that either eluded my attention or which I otherwise failed to try to operate correctly was the part of a pump-action shotgun most commonly called the action release or slide release (the latter is what I mostly hear, despite it being potentially confusing considering pistols feature that same term for a different purpose altogether).  Now, in fairness to myself, my most recent shotgun experience was with a semi-auto that had no slide and no release . . . it operated much as any semi-auto rifle.   And the experience a decade prior with a pump probably didn't feature a lot of me working the gun.   I can't even recall what kind of pump-action shotgun it was, though I do remember how sore my shoulder was.

I tell that story not to embarrass myself in regards to my ignorance, stupidity, and/or forgetfulness, though I'm sure I've succeeded in doing so.   Nor do I tell the story to regale you with overly inflated tales of my manly potency with firearms (lol).  I simply tell it to make the point that I am familiar with the general principles of many weapons of the late 20th and early 21st Centuries, and yet properly working a pump-action shotgun, cold and with no preparation, was a mystery to me.   Had yet another leftist shooter or some band of terrorists stormed the place at that moment and the kid behind the counter tossed me shotgun shells as his dying act, the most I could've done is try to use the shotgun as a baseball bat to knock the shells in the general direction of the badguys.

Meanwhile, you have Starfleet Captain Commander Benjamin Lafayette Sisko, a relative stranger to these parts temporally-speaking, pick up a period firearm and operate it just as smoothly as a Hollywood actor who'd been shown how to do it shortly before the scenes started filming.  And more than that, he had correctly assessed that he needed to do it in order to fire a shot mere seconds after picking it up to get the nearby crowd under control.   (In other words, he snatched a weapon without a shell in the chamber, so he had to rack it to load a shell in the chamber and cock the internal hammer, and if the safety was on at the time he also had to disengage that.)

How the hell did that happen?    That man should most likely have virtually zero experience with 20th/21st Century projectile weapons, and certainly not a pump-action shotgun.   And after reviewing the episode, there's no indication that he had opportunity at any point to carefully observe one being manipulated before he himself had to do so.

And it isn't as if the Remington 870 slide release is the sort of thing you could work by accident, either.  Located well ahead of the trigger on the very front end of the long trigger guard's left side, some people find that they cannot operate the slender slide release with a trigger-ready grip,    That said, it is worth noting that when Sisko first gets his hands on the shotgun, he works it like a left-handed shooter . . . that is, his left hand is the trigger hand, which would've made it easier to work by accident.   Later, he's usually running it right-handed. 

Besides, it isn't like phaser rifles have pump slide-action releases that he could've practiced with, and given Sisko's general disdain for much of the 20th Century it seems unlikely that he'd have been futzing around in a Dixon Hill sort of setting on a holodeck.   He did have an interest in early 21st Century history, but learning about history is, at least in the modern era, a very different thing than living in the moment and playing with the local doodads.

_________________________________________

Then again . . . 

After writing the above I have performed a more thorough review of the second part of that episode.  The issue I'm seeing is that folks appear to be racking the shotguns without recourse to the slide release at all.  To be honest, I'm not sure I can even see the release at the resolution available.    And of course, since no shell emerges when they rack it, then it cannot have had one in the chamber at the time.

As a rule, racking without the slide release would only be possible under a particular sequence of events.   For instance, if the weapon was already cocked and the trigger pulled with no shell in the chamber, then you would have successfully unlocked the bolt.   This allows free movement of the fore-end, meaning that if you have done this you could theoretically then rack the shotgun to load a shell into the chamber with a shell from the magazine without using the slide release.

That doesn't really make a great deal of sense unless you are expressly wanting to have to rack it to prepare to fire (as a roundabout safety precaution or for psychological terror purposes) and want to make that racking as easy as possible.   Given the user-unfriendly slide release location on the 870 I can actually kind of see this being a plausible desire, but I'm not aware of this being a big trend in the 870-owner community.

So again, that's a complete series of events that is quite unlikely for most people to engage in, and given that we also see the main "ghost" theater-major thug doing it . . . a guy who seemed intent on shooting someone . . .  it becomes even more unlikely.

One possibility is that the slide release somehow was removed from the design or otherwise became obsolete, but this would be incredibly odd.   The slide release is there because the gun, when ready to fire, is locked into battery.  If it weren't, it would be possible to fire it with the bolt partially open ("out of battery"), meaning you could have hot gas heading toward the shooter.   Without a release, the only way to unlock it is to pull the trigger.

I suppose it's possible future shotguns could be made with some sort of electronic slide release . . . that is, if there's a hand on the fore-end (or maybe a squeezing hand) and it is pulling back on the fore-end, it might 'know' that you're trying to rack it and let you do it if your finger's off the trigger.  That seems like a terribly bad idea to me and one that would most likely result in a lot of accidents, but still.   And worse, of course, is that Sisko's effortless picking up of a shotgun and perfect operation thereof is even harder to believe if you imagine he had to know how to work a shotgun totally different in operation from today's models.

So let's abandon our imagined magic slide release. Besides, in any case, we see multiple occasions where the characters rack the shotgun (with no working of the slide release) to prepare to fire, and then for whatever reason they don't fire, only to repeat the maneuver a few scenes later.   This means that they have loaded a shell into the chamber but no longer intend to use it.   A few scenes later, they again rack it (without the slide release) to prepare to fire.   Since no shell comes out, they must have removed the earlier scene's shell from the chamber.   This is not something you can generally do with a finger . . . the most common technique, as seen in this video of a fellow with his 870, is to simply hit the slide release and rack the weapon over and over again so it loads from the magazine to the chamber and then from the chamber unloads out of the ejection port.

So after completely unloading the shotgun in that fashion, they would then have to pull the trigger on an empty chamber to unlock the action and allow the slide release to live free, and then reload the magazine with shells.  A practiced shotty-lover can probably do this pretty quickly if for whatever strange reason they had the desire to do so, but most people would probably just flick the safety on.

Of course, if we assume instead that these early 21st Century shotgun models have no safety, then all the racking makes a little more sense as being the only way to safe the shotgun (i.e. not having one in the chamber).   But again, I rather doubt that the theater-major thug would have been acting like a responsible gun owner and keeping it as safe as possible . . . he would've been more likely to leave it ready to fire as soon as his finger met the trigger, even if it meant it was possible to have an accidental discharge.  It isn't like there was anyone else in the room (or even out of it) that he actually cared about.

Then again, maybe Sisko convinced him to keep it safe in that way that Sisko seemed good at in this episode.

 In short, other than the out-of-universe truth that the shotguns weren't loaded at all and were probably otherwise modified for endless racking, I don't have any good answer as to what exactly was going on, though it seems most likely that the characters engaged in a whole lot of unloading, dry firing, and loading off-camera, generally for no apparent reason.   Maybe if DS9 gets the HD remastering treatment we'll be able to see if the 870s are missing externally-visible bits like safeties or slide releases.

In-universe, the only good answer I can figure is that maybe everyone spends more time on the holodeck running amok in earlier centuries than we've ever suspected, and that working primitive projectile weapons is something that comes up rather more frequently than we ever would've suspected.

2013-09-14

The Master of Finsbury Hill

In May 2008 I started a blog entry with that title, but no text.  Can anyone tell me what the hell I was talking about?  It is such an intriguing (albeit derivative) title that I hate to keep doing what I have been doing for a long time, which is to stare at it, google at it, and otherwise waste it.

Thank you.

2013-08-14

Phaser Bank Aim Tech

Reality is copying sci-fi again as a flat immobile emitter becomes a device with wide field of fire thanks to metamaterials:

http://nextbigfuture.com/2013/08/metamaterials-are-set-to-migrate-out-of.html

Blah blah cheaper blah blah smaller blah blah better for all mankind.  Whatever.  What is *really* important here is that we finally have a plausible example of how the Cardassian square beam emitter thingy and even the Federation phaser strip could functionally aim.

Now if the guys could just put multiple devices together and have the energy combine at one point like phasers supposedly do, we could have an awesome phasery deathray.

Old TNG Advert

To the tune of "We Didn't Start the Fire" by Billy Joel... this, I may add, is from memory.  (See also:  "brain sludge" by Dave Barry)

Jean-Luc
Geordi's specs
Mysteries on the holodeck
Asteroids
Triple droids
Telepathic Betazoids
Transporter
Deadly claw
Visitor from LA Law
Photons
No Kirk
Captain has gone berserk
Shuttlecraft
Counselor Troi
Doctor Crusher's little boy
Klingon rites
Parasites
New heights
Phaser fights
Data's head
Tasha's dead
Riker's hangin' by a thread
Celebration
Transformation
Everyone to battlestations!
We didn't start the series
It's The Next Generation on your favorite station
We didn't start the series
And when we are gone it will still be on and on and on and on and on ...

I had this post to this point and was going to put more info on all the clips used (not counting the customization each "favorite station" could insert), since the last time I searched for this a few years ago the internetstubes didn't know of it.  I presumed I was the final repository of this all-important knowledge.

However, just the other day a poster on Flare linked to a YouTube video of one station's version.   Happily, then, I am no longer the sole keeper of the ancient knowledge.

http://www.youtube.com/watch?v=UumYV2jAAAw