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Civil Engineers and the Death Star

Civil Engineers and the Death Star

If it wasn’t two weeks late, this would almost be topical.

At almost 3.2×1014 kg the column would have almost enough pull, to cause near-by objects to overcome friction and drift towards it.

It turns out that there is a lot of things wrong with Death Star, from its implausible garbage shoot, gaping chasms inside rooms, and preposterously high energy weaponry. As a Civil Engineer, however, what nags me the most is the structure.

The problem is gravity.

Leaving aside the exasperation of the second, larger, model; the first Death Star had a diameter of 160km. To put that into perspective- the Shard of Glass in London is just short of 310m, or to use a more traditional unit: The first Death Star could hold almost 429 trillion elephants.

I know what you’re thinking: it’s in space- there is no gravity.

Actually the Death Star comprises 21588 internal levels stacked north-to-south, which means the structure has a ‘right-way-up’, and is simply a big space-ship with a gravity generator at the base, rather than a planetary body with an attractor at the centre. Additionally; the films never show people gliding along corridors, so it is fair to assume the Death Star gravity is 1g, just like Earth.

The loading Eurocodes are woefully unequipped for designing 21.5 thousand storey buildings. Luckily, however, someone has already worked out that the ship has a crew of nearly 1.2 million (bewilderingly this works out at an average of 53.8 people per floor). Assuming everyone weighs 80kg, the personnel load alone hits 0.9 GN.

Then you have the spaceships. It gets a little harder to work this one out, but as an engineer you have to pick the worst case loading; so assume that every ship is a fully loaded Millennium Falcon. I expect this equals out to the certainty we’re working with. That gives us an additional dead weight of 15.2 GN.

Allowing for a very forgiving 2.5 kN/m2 nominal floor and furnishing load (this is the future), the total weight of the floor structure is approximately 1’036’000 GN; completely eclipsing the weight of any of the users. The films show, however, that the Death Star is full of inexplicable holes, and therefore this can be charitably reduced by 50% to 518’000 GN.

Some very back-of-a-fag-packet maths will tell you that even if the Death Star was made of a hitherto undiscovered S1000 steel, the base of any central support pillar (allowing for distribution to the outer shell) would need to be somewhere in the region of a 500x500m solid S1000 steel column.

At almost 3.2×1014 kg the column would have almost enough pull, to cause near-by objects to overcome friction and drift towards it.

Of course, maybe it’s just held up with ‘the force’.

Editor’s Note: I have been a little too busy writing difficult speeches this week to do this topic as much justice as it deserves; something that became apparent when I discovered just how much Information there is about Starwars online. No doubt I’ll be doing a second part later this year.

As an apology I’ll tell you a secret about this site: Every single link and picture has a message that appears when you hover your mouse over them. Some of these might even be funny- but don’t get your hopes up.

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Comments

  1. @Civilpengineer

    Excellent article, lots of fun!

    How about if each floor had it’s own gravity generator built in?

  2. It did cross my mind- but considering it can’t be centrifugally generated- you’d need something with significant mass; and (so far) there’s no way of turning off gravity at a point- say the ceiling- so you’d just have a cumulative gravity effect all the way up the 25 thousand-odd floors.

    You could spread the column a little too; but it’ll all eventually end up at the bottom.

    • Fantastic post Tom. I would say that augmenting the strength of the gravity field on a per deck basis will help. Orientating the floors horizontally rather than radially would waste so much space wouldn’t it? I would have designed the floors it to layered like an onion.

      • noting the (relatively) tiny populous, wasting space probably isn’t an issue!

        like an onion would make more sense from a gravity perspective too; although it would result in a large diameter core that could not be inhabited due to the high pressures.

        frankly building massive planet sized structures is just madness.

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