Archive for the ‘Uncategorized’ Category

Paul Gilbert’s made a nice song here and plays it well. The production might be better, but I like the melodies and the joyfulness.

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Apple’s Iphone, the various Google Android phones by Samsung, HTC and probably others, and Nokia’s Symbian phones are fighting on the smart phone market. As far as I know, Iphone is “closed” and you can only download those apps that Apple lets you have. Android lets you use any apps, and I assume Symbian is similar, though I’ve heard it’s old-fashioned. I don’t have real experience with any of these phones.

What’s really missing from the palette is an open source OS.

Well, there is one, Nokia’s Maemo, nowadays called MeeGo when they started co-operation with Intel. Only one phone, N900 uses it currently. I’m waiting for the next one, N9. Just look at a source example. All graphical development is done with Qt. It’s apparently not sucky since even XFLR5 managed to move into it quickly.

I’m using Linux at home, Windows at work and a Mac every now and then, like when the Windows is acting up every day or when I’m not at home. So this writing comes from a Macbook.

I hate Windows’ instability and sucky performance, Apple’s quirks and desire to do things differently (how do I get {} brackets on this keyboard?) and Linux’ need to fiddle with configs to get things to work.

I love Windows’ hardware versatility and choice of programs, Apple’s “things just work”* approach to software and hardware and Linux’s powerfulness and openness.

As a phone, I’m using a Nokia 6310i from 2002. The battery lasts more than a week and the user interface is snappy. It has a monochrome display. Hope N9 will be ready soon. You could run Dosbox on N900. Irssi. XFLR5. Just anything. In case something goes wrong, Android will be my fallback option.

*who ever thought that waking from sleep mode should take 15 to 45 minutes,
or connecting to a wireless connection should take forever and require ten
different cross-preventing logic levels? That every week you should
download updates that would require long installing times and reboots?
That the additional desktop room should switch from the left to the right side...
Apparently, someone at Microsoft, but nobody at Apple. I don't think it's
great innovation, it's just making things not suck.

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Modern manufacturing technologies enable strange shapes and could produce unconventional pumps. What is good for small scale rockets if turbines and centrifugal pumps have too much tip losses?

Rotary engines have vastly better power to weight ratios and vibrate less than piston engines. They’re also expensive and hard to build (cue modern manufacturing again). Here is one demonstrated in a paramotor, Parajet Cyclone using a Rotron engine. Love the music.

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Well, scaling seems to be my pet issue. I recently wrote something not entirely well reasoned in a comment at Paul Breed’s. (For some reason Chrome complains about blogrolling.com malware there so continue if you’re sure you’re safe.)
So let’s make it better. (A word of caution though, I’m quite sleep deprived now.)
For those who like to jump into conclusions, it’s going to be like this all over again.

Assume a pressure fed rocket first stage has a certain propellant chemistry, tank and thus chamber pressure and must operate in the atmosphere, hence has a certain exit pressure (0.1 MPa or 1 bar or 15 psi is the optimal). Then it has certain thrust per nozzle area.

Now, the rocket needs thrust to lift off. If we assume a constantly scalable shape, its mass will be base area times length times density.

Since the maximum fittable nozzle exit plane also depends on the base area, we find that for a certain area, the rocket can only have so much mass – or that the rocket has a maximum density times length parameter. If we assume the propellants have been picked early on, density is set and the rocket only has a height constraint.  Each pressure and propellant chemistry basically has a “characteristic length” that can’t be exceeded. Otherwise it can’t lift off.

The higher the exhaust velocity, the smaller the nozzle, so raising chamber pressure reduces the needed nozzle size per thrust and the rocket can be lengthened.

For small rockets, I’d hunch that they have little length and thus they don’t really have to worry about this. They can be as thin (and thus long) as practical, to try to avoid drag losses.

For upper stages, the thrust to weight needed is less and the weight even less so it’s even less of a problem – except that the expansion ratios can be huge since there’s no back pressure anymore. Still, with small rockets, pretty huge expansions might be possible without having much problems because the second stage is very small (=also short) anyway and thus there’s little mass per nozzle exit plane area.

On really tall rockets like Saturn V, the thrust per base area has to be huge, hence it had to have those base extensions for the corner engines (note how the N-1 had a conical shape with a wider base, the engines had a bit higher pressure but the upper stages were kerosene – these cancel out a bit but the base of the rocket had some empty space) . Similarly with STS, putting so much thurst on the tiny orbiter’s tail required high chamber pressures and some tail shaping

I don’t have any numbers handy, but if we assume a 10 m tall 1000 kg/m^3 density (water) rocket, then it has 10,000 kg per m^2 or the thrust required for a 20 m/s² acceleration is 200,000 N/m^2. This is easily achievable. With an exhaust velocity of 2000 m/s, the mass flow needs to be 100 kg/(s*m²) to produce that thrust. Again with the exhaust velocity that mass flow means a density of 0.05 kg/m^3. Air’s density is 1.2 kg/m^3 at 300 K, so that’s 20 times less dense which means hotter, the density is like hot air at 6000 K. Though the molecules might be mostly lighter OH instead of N2 and O2, making that rocket exhaust at 3000 K for the density. Rocket exhaust isn’t that hot – it’s cooler and denser and thus more thrust per unit area.

For a second stage we can look at the pressure fed AJ-10 from Delta 2: 1.7 meters diameter (certainly constrained), 40 kN of thrust. For a T/W of 1, density of 1000 kg/m^3, we get 4 tonnes and 1.7 meters of depth. Quite a stubby stage with a roughly spherical tank! Isp is 321 s. The real Delta II second stage weighs 7 tons and the payload is some too, but reusable rockets won’t have such high performance first stages (nevermind solids!), so they might need more T/W.

Oh, BTW, I assume three stages to orbit for pressure feds though I haven’t looked it that closely.  Mass ratios and ISP:s I’ve only hunched.

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There’s a free lecture series (it’s also a course but attendance is open) at HUT Aalto University about new energy technologies, organized by a friend of mine who works at the lab there. Here’s the lecture program (they will be held in the mechanical engineering building):

Thu 9.9. Introduction. Prof. Markku Lampinen: Energy conversion – From nanomachines to renewable sources.
Thu 16.9. CO2, greenhouse effect and climate change. Dr. Jouni Räisänen, University of Helsinki
Thu 23.9. Looking for a carbon storage, biochar as a win-win solution. Dominic Woolf, Swansea University, UK.
Thu 30.9. Biomass solutions for replacing coal: biochar, biomass gasification, multifuel power plants. Jukka Rouhiainen, Helsingin Energia.
Thu 7.10. Research on bioorganic fuel cells as power sources.
Professor Yohannes Kiros, KTH, Sweden.
Thu 14.10. Microturbines, a technology for local energy production. Professor Jari Backman, Lappeenranta Technical University.
Thu 21.10. Energy efficiency – “Negawatts” for cheap.
(Thu 28.10. middle term exams)
Thu 4.11. Wave power. Dr. Ana Brito e Melo, Wave energy centre, Portugal.
Thu 11.11. Geothermal energy, overview and the possibilities. Professor Eva Schill, Université de Neuchâtel, Switzerland.
Thu 18.11. Grätzel solar cells. Millennium prize winning breakthrough in solar energy.
Thu 25.11. Energy solutions for traffic – Which will win?
Thu 2.12. Student seminar
Thu 9.12. Student seminar (last lecture/seminar)

Reserve topics:
Wind power.
Passive heat technology/thermal engineering.
Solar thermal energy (STE).

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Jon Goff’s Move

Oh, what a bombshell, he’s leaving Mojave too. After Ben Brockert and Ian Garcia, there’s not that many from the Xombie/Xoie team left, but they got new people in and are moving on with the CruSR commercial sounding rocket things. And the bigger part is that Jon is founding a new company, Altius Space Machines, which only says “Building sustainable space infrastructure through low-cost space machines” on the homepage. We’ll see.

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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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