Archive for the ‘Homebuilt’ Category

Or The Space Game, by ESA.

The Space Game Screenshot

Minimize delta vee by moving the planets around (this changes the probe's arrival time at the planet). This shows my best solution so far, with some playing one evening, about 13 km/s

This is a nice javascript webpage where a probe is shot from Earth to Jupiter with gravity assists at Venus (twice), Earth and Mars. You try to achieve the lowest propulsive delta vee. You decide when the spacecraft arrives at each encounter and the program basically calculates the rest. It’s quite a nifty little piece of Javascript, the future of web applications is like this. It works fine with Chrome on Linux at least. Probably IE will have problems but who uses that anyway?

I’m ranked at #39 at 12.74 km/s… Far behind the gurus who get below 10 km/s readings! There are apparently some prizes for the top three, but I think people are in it for the fun of it.

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Most people with interest in aerospace history know of Barnes Wallis’ geodetic structures, most famously used on the Vickers Wellington. He first invented them for the R100 airship, basically a weave of thin aluminum shapes going in different directions, forming a grid. No bulkheads or even wing spars needed, but it was quite complicated to build. Fabric was used as a cover, first linen and later thin steel wire mesh. It became outdated when airplanes were pressurized and moved to aluminium monocoque structures.

Vickers Wellington with some skin shot off

Well, now, airplane manufacturing technologies are changing again, after some 70 years of riveted aluminium sheets, bulkheads and spars. Composites laid by robots enable fancy shapes, and optimizing the strenght carefully in various directions. Boeing has been looking at a 737 replacement. So far, pressure hulls have had to be cylinder or ball sections – only that way the thin skin can be in pure tension, the only force it can really resist. Often a double bubble has been used, with the cabin floor dividing the lower and upper half into two circular sections and also keeping the left and right side together at the same time. A circular frame is not very space efficient for humans though, so Sankrithi et al at Boeing figured out how to put fibers in a grid to enable a roughly elliptical shape that is wider than it is tall. The advantages are not entirely clear to me from their description, since they seem to say the ratio of seats per circumference is similar to a circular frame, but it is nevertheless interesting. (Also, it’s strange that Free patents online shows that the patent was filed in 2009, yet Google shows it was filed in 2005, yet they seem the same at first glance).

Fiber reinforcement grid geometries for an airplane fuselage

This has some relation to the X-33 where they also attempted non-cylindrical composite pressure vessels. The technology has advanced since though.

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Huh, it always takes a long time to find anything on web pages that are so cluttered up. Here. No idea what the MPGe or miles per gallon equivalent is.


Here’s ERA’s video (they didn’t win, although they were very close. I think they were penalized for driving too fast):

Holy crap. Their vehicle has 1000 Nm torque and does 0 to 100 km/h in 6 seconds.

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I have to admit I was skeptical at first. What can a pile of trash bricks, mud and sand do, on a barren poisoned wasteland? Or some pouches of dirt around this and other abandoned post-industrial zones in the city? Apparently, a month later, the most awesome party ever, where everybody makes their own pizza and bakes it in the centerpiece of the whole happening, Archie the dome oven. Pumpkin, Zucchini, Beetroot, Onion farmed by the city farmers. Even the honeybees had participated. A huge thanks to everyone!

People building archie the clay oven in Helsinki

Building Archie

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It doesn’t have the same sound as “The Last V-8” now does it? When you look at what’s happening in the world of automobiles, you get some idea of a change. It is always slow, yet I predict that when it happens, probably starting before the end of this year, people are taken by surprise.

Why Would Anyone Buy A Hybrid Car?

It doesn’t have that much better fuel economy than a modern petrol or diesel engine if you drive out of the city, and it costs some more and is complicated. New turbocharged and variable valve engines can do pretty well because they can be built to opearate in a flexible manner. BMW has even introduced a technique that could be called a “virtual hybrid” – where the aircon compressor and battery charger are disconnected when the gas pedal is pushed to the bottom, resulting in extra power available for traction – allowing a smaller engine to achieve the same acceleration.

In some cases, like buses that need to stop often, hybrids make great sense, but otherwise I see the improvements in ordinary direct internal combustion engine driven cars narrowing the gap quite considerably. On the highway the hybrid has no advantage.

A Seemingly Small Addition

Volvo V70 Plugin Hybrid Prototype

So, add a grid recharge capability and you have a plugin hybrid. By itself that’s not much yet though, you have to enlarge the batteries too. Since most trips for most people are commuting and errands, they’re short and can be done entirely on battery power. You also still haul the gasoline engine along and it is used on longer trips. Most problems solved right here? Sounds easy.

Chevy Volt / Opel Ampera is coming soon. And just take a look at the huge number of plugin hybrids being developed, listed at Plugin America. Most of these will be dead ends, but some might make it big.

Pure Electric Cars – The Charging Problem

The problem is, gasoline is very very energy intensive. If a car uses 8 L for 100 km and a 10 kWh worth of energy, then tankage of 40 liters gives about 50 kWh of energy. Done in 50 seconds this stream of gasoline through the hose is worth 1 kWh per second or 3.6 megawatts. High enough temperature superconductors have not yet been invented that would make a hand-attachable 3.6 megawatt car charger possible. If we generously assume 240 Volts and 40 Amperes, the charging power is only 10 kilowatts. The largest home appliances like sauna stoves and water heaters are in the single kilowatts range. They often use 380 V three phase power here, but that gets slightly impractical for a car charger. This thousandfold disparity in energy replenishment speed is striking. An optimistic 10 kW charger would charge a 100 km drive’s worth of energy in an hour. Certainly useful for commuters. Charging as range extension seems doubtful. Our summer cottage is 300 km from Helsinki. If a full battery only lasts the first 200 km, one would have to stop at a loading station for one hour before one could drive the rest of the way. Not realistic. The penalty of lugging around the heavy and complicated IC engine has to be bitten at this point of battery development.

Battery Improvements?

There exist some pretty high energy per mass battery technologies right now, but they are expensive and use rare materials like cobalt that they can never really be mainstream solutions on something that stores energy in the megawatt hour class. Hopefully with enough money now available, some cheaper and less material intensive ways to store electrical energy can be developed.

Your Local Correspondent

Naturally, Finland would be a pretty ideal place to have electric and plugin hybrid vehicles. A significant portion of the populace keeps their cars parked in a spot with an electric socket nearby – those house timers that turn on the cylinder block heater on an hour or so before leaving for work in the wintertime, meaning less fuel use and wear for the engine. It is trivial to use those 240 V outlets for electric car charging. Also, electric cars are actually manufactured in the city of Uusikaupunki, Finland by Valmet. The Th!nk City is one. Too bad because of insane tax policies, it is not actually sold here – at the moment you can only get them in Norway, Austria and Holland. The Fisker Karma electric sports car will also be manufactured in “Uki”. I think they have a long nose on the car for Freudian reasons – since it doesn’t need to hold a long block internal combustion engine – or maybe it’s just that buyers are conservative. And then there’s the e-cars now project aiming to refit old Toyota Corollas with electric motors and batteries. But there’s more.

Automotive X-Prize

There’s that going on, which is actually interesting! My favorite vehicle is the Peraves E-Tracer.

Here are the results from August 2 but I still don’t know what will change / what is coming because the pages are unclear: [EDIT: fresh info at the blog indicates some testing is still going on]

1st Place Team Lithium Ion Motors of North Carolina (125 MPGe average fuel economy for the event)
2nd Place RaceAbout Association of Finland (0.179 seconds behind the leader and 100 MPGe average fuel economy for the event)
3rd Place TW4XP of Germany (11 minutes, 36.9 seconds behind the leader and 139 MPGe average fuel economy for the event)
4th Place ZAP of California (DNF – 48 laps completed)
5th Place Aptera of California (DNF – 18 laps completed)

The Raceabout team is from Helsinki’s Metropolia university of applied sciences. They have a long background of building electric vehicles, and it’s nice to see something in the competition that looks like an actual car, yet still manages to do so well.

RaceAbout's E-RA vehicle in the Automotive X-Prize 2010 competition

Hopefully the politicians here can get something sensible done, and the super-high taxes on electric vehicles (basically, anything that isn’t gasoline or diesel is considered fishy and is taxed hugely) can be dropped so we can start seeing more of them here! The current situation is a travesty!

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Gah, got tired of monkeying around with various software (XFLR5 is never provided as an executable on ANY platform despite countless requests, just some packets) so loaded up a profile in Matlab and plotted it in multiple sizes and printed those. Took only a few minutes. It’s still the best software ever.

It went something like this:

load MH78.txt %text file is copy-pasted from MH-aerotools.de
whos %check out if it worked
MH78 %check out what we just loaded
axis equal
legend MH78
%perhaps print here if it fits on one paper

%this is three views for a larger print:
xlim([0 0.4])
%print here manually
xlim([0.3 0.7])
xlim([0.6 1])
%Etc you get the idea...

Had to read some documentations for this, but the gist is that Matlab actually has some proper documentation. I just typed help gca, help set, help axis, help axes, help xlim etc and they contained some quick examples that I then tried and got the hang of everything. Matlab should be the gold standard for all similar software developers. I’ve tried coding in Python and Scilab and both have large stumbling blocks in quick and efficient numeric work.

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This is something we’re after.

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