Random Question + Nuclear Bomb

[Ice97531]

Lets pretend that it is possible to make a box, roughly 4’ x 4’, that can withstand a nuclear explosion.
Then lets pretend Hermand places this box on top of a nuclear bomb, lites the fuse, and gets inside his box.

How far will Hermand fly?
What forces will he feel?
Will he be blasted into outerspace?

[sleestak]

What size bomb?

Slee

[Ice97531]

Like this big:

http://www.hometheaterforum.com/htfmeets/obi9-99/dabomb.jpg

(BIG)

[Mangetout]

He won’t feel very much; we’ve alsready assumed that the box is made of some magical material capable of withstanding the energy of a nuclear explosion, but the passenger is an ugly bag of mostly water - the rapid acceleration is going to turn him into soup.

I don’t think he’d be blasted into orbit, let alone outer space - there’s a heck of a lot of air resistance to overcome on the way up, as well as gravity.

[Ice97531]

Well then picture this:
The guy inside has a special suit on so he can’t be turned into soup…or whatever…ignore the soup thing
Also the box is no longer a box but an areodinamic marveal that has minimal air resistance
What then?

[Desmostylus]

http://www.geocities.com/CapeCanaveral/Hall/1892/sputnik.html

Every kid who has put a firecracker under a tin can understands the principle of using high explosives to loft an object into space. What was novel to scientists at Los Alamos [the atomic laboratory in New Mexico] was the idea of using an atomic bomb as propellant. That strategy was the serendipitous result of an experiment that had gone somewhat awry.

Project Thunderwell was the inspiration of astrophysicist Bob Brownlee, who in the summer of 1957 was faced with the problem of containing underground an explosion, expected to be equivalent to a few hundred tons of dynamite. Brownlee put the bomb at the bottom of a 500-foot vertical tunnel in the Nevada desert, sealing the opening with a four-inch thick steel plate weighing several hundred pounds. He knew the lid would be blown off; he didn’t know exactly how fast. High-speed cameras caught the giant manhole cover as it began its unscheduled flight into history. Based upon his calculations and the evidence from the cameras, Brownlee estimated that the steel plate was traveling at a velocity six times that needed to escape Earth’s gravity when it soared into the flawless blue Neavada sky. ‘We never found it. It was gone,’ Brownlee says, a touch of awe in his voice almost 35 years later.

The following October the Soviet Union launched Sputnik, billed as the first man-made object in Earth orbit. Brownlee has never publicly challenged the Soviet’s claim. But he has his doubts.

By the way, the velocity required to escape earth orbit is about 25,000 mph. That means the lid would be the fastest man-made object in history to date, traveling at around 150,000 mph (at launch - it would be slowed some by earth’s gravity on its way out). The fastest objects otherwise are the Voyager 1 and 2 spacecraft - now beyond what would commonly be termed the solar system - which are traveling 80-something thousand mph relative to the Earth and 30-something thousand mph relative to the Sun.

[Ice97531]

Any idea on how many G’s Hermand and his flying lid would feel?

[edwino]

That bomb isn’t that big. Looks like a mock-up of Fat Man, which was around 20 kilotons when dropped on Nagasaki.

That’s about the size of the Trinity bomb. There is a famous picture series of Trinity (see here) taken at 6 and 16 milliseconds post explosion. They have a 100 meter ruler on the bottom of the picture. At 16 milliseconds, the fireball is roughly 100 meters around, accounting for the 30 meter test tower that the “Gadget” was mounted upon.

Assuming no air resistance and constant acceleration, acceleration can be calculated by a=2x/t[sup]2[/sup]. x=100 meters, t=0.016 seconds. So a=200/0.000256 = 781,250 m/s[sup]2[/sup], or 79,719 * g. He would be mush.

[Mangetout]

I was under the impression that the story Desmostylus links was either unsubstantiated or an outright hoax - didn’t we have a thread about it? I may be misremembering.

[Desmostylus]

You could well be right Mangetout. I’ll try to find the earlier thread.

[Mangetout]

Here is a link to an earlier thread discussing the same (or a similar) story; the thread includes a tantalising no-longer-working link to what is implied to be a NewScientist article debunking the account.

[Desmostylus]

I couldn’t find the earlier thread, but I found this instead:

http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html

In the event, the cap appeared above the hole in one frame only, so there was no direct velocity measurement. A lower limit could be calculated by considering the time between frames (and I don’t remember what that was), but my summary of the situation was that when last seen, it was “going like a bat!!”

As usual, the facts never can catch up with the legend, so I am occasionally credited with launching a “man-hole cover” into space, and I am also vilified for being so stupid as not to understand masses and aerodynamics, etc, etc, and border on being a criminal for making such a claim.

So yeah, the story I first quoted is crap.

[Desmostylus]

Thanks, Mangetout. That explains where I first heard the story. Dr Karl.

[Padeye]

That’s a faulty assumption *Edwino that the velocity of the expanding fireball has anything to do with the force exerted by the blast. Even if it was an accurate representation of the force it might be noted that a 4’ cube of unobtanium will accelerate somewhat slower than a pressure wave in air given the same motive force.

[Flander]

I think if you remove the person from inside the cube, it would make things a lot easier. It isn’t really necessary to have a guy haning out in the box, just adding “dead weight”. Also, consider making the object a sphere. That way, the drag coefficient is the same relative to the objects orientation. Of course, getting the sphere to balance on the nose of the bomb is your problem.

[Ice97531]

Hermand is just there to make you laugh…just ignore em in your mathematical eqautions guys
For the balancing act…hmmm
Just put the bomb face down
The fins should do the trick:D

[edwino]

Yes I see the error of my ways Padeye. It’s why I’m in biology, I suppose. I just figured the shock front at the edge of the fireball would be dense enough to propel anything at the rate of the expanding fireball. I once read somewhere that the density of an expanding shock wave from a nuclear blast approaches steel. I have no cite, so I’m not sure if that is BS.

[An_Arky]

So, Ice97531, is this a particularly difficult homework assignment?