Tuesday, 23 June 2020

Kerbal Space Program

I haven't played video games since the days of GTA3 on PS2. After weeks of boredom I bought myself a computer specifically to play a very niche, 5+ year old game. Kerbal Space Program is about space exploration. The characters looks funny and childish and there are lots of silly jokes in it. Despite that it's a deeply technical and difficult game. You have to design rockets and spaceships (from a large collection of parts which stick together like lego) and fly them to other celestial bodies. The game doesn't place any limitations on your designs or flight profiles except for actual physics. Gravitational and aerodynamic forces are modelled accurately.  Physical and thermal stress and deformation of all the parts are modelled. The orbital mechanics is accurate and difficult.

Yesterday for example I was at a moon and realized that I had no idea how to initiate a transfer back to the planet because I was on a polar orbit (the plane was normal to the moon's orbit). The answers seem to be 1) wait ¼ of a month 2) spend a huge amount of Δv on inclination changes 3) if the gravity is low enough escape northwards and start from there.


My favourite thing about the game is what's called "emergent narrative". The designers didn't have script writers, and they never wrote any story lines for me to enjoy, but I find myself with a fascinating challenge that just emerged from the lower levels of simulation. I was in upper atmosphere doing about 3km/s when I discovered a design flaw with my vehicle. The strong experiment storage vessel bridged the gap between the crew capsule and the spent fuel tank that I was trying to eject. The explosive bolts had fired but the bottom half of my rocket was still tied on. When everyone survived and the experiments were recovered it felt like a real achievement.

Richard "Hohmann Transfer" B

Thursday, 18 June 2020

Problem Drinker

I used to go out with a girl who was so unused to drinking that she once woke up (on new year's day) and couldn't identify the mystery illness with which she had been afflicted. It was characterised by headache, nausea, thirst, dizziness and hypersensitivity to noise. It turns out I'm no better. When I visit my mum for lunch she will usually offer me a bottle of exceptionally week Dutch lager (I think it's 2.6%). She will have a small glass of sherry and I'll have the lager as an aperitif. A couple of weeks ago the brand of lager had changed. She didn't mean to do it, but she had tricked me into drinking a bottle of really strong lager (quickly) on an empty stomach. That afternoon I was unusually tired, but in a cheerful and confused way, and my motorbike seemed exceptionally heavy and difficult to operate. I didn't work out why I felt so weird until the next time I was visiting my mum and was offered another bottle of the export strength lager.

Richard "a.b.v." B

Tuesday, 9 June 2020

It Was This Big

How big is a spanner?  They all have some markings on them, but it's not always the gap between the jaws. For AF spanners the number written on the spanner is the gap between the jaws in inches (ignoring a little clearance so that it will actually fit over the bolt). For Metric spanners it's the same, but in millimetres. For Whitworth spanners the number is the size in inches of a hole, through which the shank of a well designed bolt would fit, and the head of that bolt would fit between the jaws. For BA spanners it's an arbitrary, usually even number that gets bigger as the spanners get smaller.

That's all well and good, but what does a measurement of length really mean? You've got a ruler, but you just assume that it's got the same measurements on it as all other rulers, how can that possibly be organised? Where did the first ruler come from? The factory that made your ruler had their tools calibrated in a laboratory. That laboratory had their tools calibrated by the National Physical Laboratory (or your country's equivalent) and the NPL compares their reference length against two scratches on a bit of copper stored very carefully in Paris. We've all just sort of quietly agreed that those two scratches are a good distance apart. When it comes right down to it, describing the size of something is just comparing its size to something else.

I had to buy a socket in the wildly inconvenient size of 1 and 5/16 of an inch (AF), while it does have this number on the socket itself, the packaging has a far less useful (although somehow more honest) description of the size. It says "Classic size for Hub Nuts on Mini, MGB and Triumph TR4". It's not a measuring convention that I want to start using in my tool box.

Richard "0.01959 Smoot" B

Tuesday, 2 June 2020

If the Cap Leaks

Car maintenance meets automotive history. The cap on the brake fluid reservoir on my sports car is leaking a little bit so I wanted to replace it. Caterham don't have them in stock, and they're overpriced so I decided to shop around. The threads for the cap are the old fashioned Girling/Lucas ones and the master cylinder is made by AP Racing. I could easily get a cap that would fit from any racing car supplier - hell you can buy a genuine Girling one from Demon Tweeks! The problem is that mine's a road car and it needs a fluid level warning switch (it doesn't strike me as a bad idea on a racing car even if it's not a legal requirement). The warning switch is integrated into the cap. I refuse to believe that Caterham are making their own reservoir caps, so the question becomes: where did they find a brake fluid reservoir cap that will fit an elderly British car, or a racing car, but has a fluid level float switch built into it?

Half a day of googling later and the answer is obvious: Late model classic mini. When they started making minis they would have been using Girling master cylinders, or something compatible. At some stage the law changed and they had to have a warning light for the fluid level, they didn't change the master cylinder, they just cut a hole in the cap and bodged a crappy float switch into it. The part number is GRK6009 and they're available from all the people that look after old minis. It looks like a rush-job, the design is terrible and the lands for the gasket are tiny. Frankly I'm surprised that it kept the fluid in for this long. I'll probably make my own out of a real cap and a modern float switch when I take the car off the road at the end of the year.

Richard "Yes I do believe that I can make a better job of it that Austin-Rover" B