May 19th, 2010

Mad scientist

Hints to the busy scientist...

...Don't assume that scientists are the only people who use the equipment you need. Occasionally you'll discover that there's a much bigger market out there, and one where the vendors sell at much lower prices.

For example, someone from another school was asking about the price of vacuum pumps on a technician's forum. It happened that I was looking for a supplier of vacuum pump oil that morning, so I had all the main educational catalogues open, and found something suitable at £260 from one supplier, £318 from another, for identical pumps.

So just out of curiosity I took a look on eBay, and found a supplier offering new vacuum pumps with a better specification for £167 including delivery, and one with a slightly poorer specification (but probably still good enough for education) for £109. It turns out that schools aren't the only people who use vacuum pumps; air conditioner and refrigeration installers use them too, to remove dissolved gasses from refrigerant. It's a big market, and one I'd never realised even existed.

Another time I wanted silver foil to make electrodes. It was about £25 for a fairly small bit from a laboratory supplier. We ended up buying it from a place that sold jewellery fixings - paid £8 for considerably more.

Needless to say all of this applies to anyone else who needs to go shopping for apparently specialised items - find out who else needs it, and where they buy it, you might be pleasantly surprised.
Planets of Peril

Spaceship design template

I've written a spreadsheet for spaceship design for the Weinbaum universe - if anyone wants to give it a try right click and download from

The data saved with it is for a small fast short-range racing ship.

Going down the page, the type of atomic blast determines its efficiency - Uranium blasts are cheapest and least efficient, but have minimal running costs since they use salt as fuel. Protactinium is best but hideously expensive to run, since the fuel is lead.

Emergency acceleration is normally used for a few minutes at the beginning and end of a flight; cruising acceleration is used for weeks on end, and is much more efficient. The higher either is, the more the engines costs and weighs, but the major factor is emergency acceleration. A racing engine can run at emergency power for much longer without melting / exploding, but you pay a hefty premium in weight and costs.

Flight duration determines the mass of supplies you need per trip - e.g. oxygen, water, food. You have to build for the maximum journey planned for the ship, e.g. a trip to Mars is just under two weeks at .03g.

Horizontally landing ships are better for military use and exploration, but add a lot to the cost of the engine, plumbing, etc. Most ships take off and land vertically.

An algae "farm" is most useful on long flights / big ships, it's heavy and expensive but reduces the other supplies needed by a third.

The rest should be fairly self-explanatory, I think.

I think it's moderately bullet-proof if you don't disable protection, let me know if I'm wrong. If there's anything you don't understand please ask below.

One thing - I haven't tried to have fuel tank size determined by flight duration since there's a circular argument in there - the best way to work it out is trial and error. For the sample ship changing the fuel mass has some very interesting and somewhat non-intuitive effects on maximum flight time at emergency thrust and total price - doubling the fuel load gives just 13 minutes more thrust and nearly doubles the price!

later Just tried this on another computer and a couple of the columns are a bit too narrow - it's easily fixed, just unprotect the sheet and drag them a bit wider. I'll upload a revised version tonight.

much later OK, forget it for now, I need to rework the fuel consumption and engine size formulae a little, it's virtually impossible to design a ship that'll go much past Mars.