24 posts • joined 7 Jul 2008
..Because rubber will behave very strangely in space / on Mars (Not to speak of the problems with de-pressurizing and re-pressurizing them).
You get degassing, temperature effects etc.
The moon rover wheels were not made of rubber. They were made of metal wire and plate:
Re: Energy density
I looked at the article, but did not see the table.
596 Ah kg−1 at 0.5V yields 298 Wh/kg, which fits to 15% maltodextrin (24 e) found in "Supplementary Table S3 Comparison of energy densities of batteries and EFCs". If I read the table correctly, then this means that the 298 Wh/kg relates to the fuel mixture, not to the complete system.
Li. Ion: 180 Wh/kg is a reasonable value for a cell with good power and lifetime values. I know of alternative chemistries that have achieved 300 Wh/kg in lab conditions.
Although I would be happy to see a good and lightweight fuel cell that can use this fuel, I fear that the 298 Wh/kg will be slashed substantially for any application that is not "low power over extreme intervals". Even for such an application, 298 Wh/kg is not "one order of magnitude higher than that of lithium-ion batteries". However, it is also not one order of magnitude less, which means that this is a technology to keep an eye on.
Energy density is measured in Wh/kg.
Proclaiming an energy-storage density of 596 Ah kg−1 is meaningless, because the voltage is missing.
I could claim that our drive battery has an energy density of 10000 Ah/kg simply by lowering the output voltage sufficiently (using a DC/DC converter).
Also, seeing that this is a fuel-cell, not a battery: What does the mass data relate to?
Mass of fuel cell alone? -Then they should compare to other fuel cells, not to Li-Ion.
Mass of fuel cell and fuel? -Then it is easy to fake good results by combining an oversize large fuel tank with a minuscule fuel cell. .. Which, when taken to the extreme, equates to the energy density of the fuel alone.
-Which is also quite misleading. We fly some 500 km on 5 kg of hydrogen. Sounds nice?
Wait until we have added the weight of the fuel cells, the peripheral systems and the pressure vessels.
El Reg is not at fault here though. Whoever wrote that press release either was being willfully misleading or ignorant of the matter at hand.
I have previously had artwork published, but I never expected to see my "flying pig" joke picture published in the noteworthy el Reg!
The picture used in the link uses a 3d model that I in my former life generated for open source (slow)MMO found at www.worldforge.org combined with a pair of wings. I hacked up that picture in order to convince another contributor that it definitely was the right time for her to release some more artwork.
Some years ago I noticed that someone had contributed the picture to wikipedia http://en.wikipedia.org/wiki/File:Flying_pig_hell_freezing.jpg , pretending to be the creator. Have never bothered to rectify, but think it is funny to be the creator of the most used "flying pig" image available in the interwebs (says something about the quality of the net doesn't it?).
some more piggyness:
Re: That's some battery
We have a product with an automotive size battery pack. early units have been in customer hands for eight years now, and we see no degradation.. so yes it is possible.
Note that the 8 years are with regards to natural aging of the cells (which is mainly dependent on charge state (higher is worse) and storage temperature (higher is worse). Each charge cycle also has an effect on battery life, but if you buy good cells, then you can get more than 4500 SAE cycles (80% discharge - recharge). I am convinced that we will all be driving electric cars in a not so far off future. The advantages are simply to many, and the technology is progressing steadily.
Re: Lots of dots
Here is a link which describes a working open source tool-chain very well:
The core program is visual sfm:
I tested it using reduced resolution (as suggested in the article) and the results came out surprisingly well.
Following the article, the whole tool-chain is surprisingly simple to follow. Add a 3d-printer at the end, and you can set up your own business.
However, Note that the software requires a non-transparent surface with texture in order to work well.
A uniform white box tends to end up with only the edges being detected, and with gaps in the sides.
Re: I call bullshit @Holtsmark
Nope, it is not fear.
I have spent the last 4 weeks fixing under-defined models where the "engineer" created parts with "wide sweeps of his hand". I would LOVE tools that would speed up my work-flow more while yielding well defined models. Such tools would not lay off engineers, but rather result in the same amount of engineers (there is never enough of us) produce more refined designs.
However, having world + dog bow before Mr Musk and his new way of using BOTH HANDS to view an object where a single hand plus an input device, or just head + Track-IR could do better (Leaving one or two hands to actually work the model), then thats when I CALL BULLSHIT.
And yes.. It is only proof of concept. However, the proof should show a little more novelty before it becomes a newsworthy "breakthrough". There is enough cool engineering out there that does not get coverage.
I call bullshit
Spending my day designing Aerospace parts in CAD, I can not come over the impression that this is pure management porno.
Engineering is parameter driven. All important thicknesses, angles, lengths are set by entering numbers on a keyboard (or using filtered output from computer analysis). You do NOT gesture a wall thickness of 2.467885423456mm, instead you enter 2.5 mm on your keyboard
All that I can see in the video is some manager impressing other managers by using hand gestures to move around an ALREADY ENGINEERED part.
This is NOT progress
Re: "clearly Top Gear"
I did read the bit about "open source" and "low cost". However, the post I replied to described this in "leading edge" terms, and I therefore noted that leading edge was already quite a bit further.
That this comes at a price is quite clear, but the users seem quite happy with what they get for the money.
If proxydynamics has been all over the place for a while, then I have not noticed.
All in all, it is nice to see development moving ahead. Now I am only waiting for an available certified sense and avoid system, and interesting things can start to happen.
"clearly Top Gear"
impressive as this is, "Top Gear" is already for sale.
These guys http://www.proxdynamics.com/products/pd_100_prs/ have obviously already achieved a much higher degree of integration and miniaturization, they just prefer to keep a somewhat lower profile than your usual academic research group. Only problem: you can not buy it unless you have government backing :(
Black helicopter because the gray helicopter icon is missing.
Re: LiPo at altitude
"LiPo capacity drops nearly exponentially with temperature.
I suspect it needs to keep itself warm as much as it needs to keep warm the motor. That will add some more weight and logistics around insulation."
First: Use low temperature capable cells.
Second: Insulate them well (keep them inside truss payload compartment
Third: Do something like this: http://lange-aviation.com/htm/english/products/antares_20e/img_battery_module_xl.html
The red stuff is the battery heating wrapped around 3 individual cells.
LiPo at altitude
may I respectfully suggest that you load-test LiPo in REHAB?
LiPo usually is kept together using the coffee-pack principle, meaning that the active ingredients are inside an air-tight bag at (close to) vacuum. The outside air pressure then presses the cathode, the conductive polymer and the anode together, do that beautiful chemistry may occur. Remove said air pressure, and chances are that the spark will be missing, with the sad result that LOHAN will fail to see an ejection while suspended under her massive orbs. Should LiPo fail in REHAB, then you may want to consider using potted Li-Ion. The hard enclosure means that energy/weight is somewhat reduced (chemistry can be the same), but these batteries can work successfully in space (check specs for individual cell types).
Also note that you will get more energy out of the pack if some energy is used to keep the pack itself at temperature.
..mine is the one with a 12.5 kWh / 289V space grade Li-Ion pack in the pocket...
I build these things for a living, and although I do not doubt that the wings will reduce the rate of decent somewhat ("fly"), I am sure that weight could easily have been reduced substantially, and performance increased. I will spare you the long and tedious analysis.
The additional strengthening of the fuselage will indeed undergo tension, so unless the but-end glue joints have been strengthened locally, the tubes will probably do little.
To all who discuss levers: The bending force created by the aerodynamic lift is simply carried over into the other wing (assuming continuous wing spar. All the fuselage sees is an upwards force, no bending force.
Anyway: Good luck on Saturday. Bring enough alcoholic beverages to either celebrate or forget .
Not enough oxygen available at critical altitude.
Chemical or electical solutions may be better. If you go electrical: LiPo batteries may have problems due to lack of external atmospheric pressure to keep the (vacuum-) pack together and working. Go LiIon with a cylindrical metal shell if you can. Make sure that the battery heats itself as well.
Not impressed with weight of box. Better get someone to sponsor you with low density Rohacell foam. Extremely good insulator as well. Glue it with epoxy or polyurethane and skip the duct tape. .
Blender 3d is a clear winner in this field
Chasing the wrong program
Sadly, the moment FreeCAD approaches AutoCAD capabilities, the developers will discover that most engineering (Not Architecture) is performed in parametric modellers like SolidEdge, SolidWorks or (Ugh!) Pro-Engineer. (Or CATIA, if big wealthy Aerospace or Automotive companies are involved)
I never touched AutoCad again after I started working with these. In my experience, ONLY architects still work in AutoCAD. ..And I do design stuff that is slightly more complex than a custom tray...
The penguin? ..because I actually have a fully parametric solid model of him laying around somewhere on my HD.
This is not a pulse jet engine.
Pulse jet engines, like the WW2 Argus engine uses reflected shock waves both to inhale fresh air and to create sufficient compression of the fuel-air before ignition.
This invention does not appear to use shock waves, and appears, technically to be closer to a quite normal two stroke engine. Sadly this does not make for a just as good headline, since Mr. Page cannot insert NAZI into it without looking ridiculous.
"Nazi-WV-beetle-powered father of all paintball guns patented" really does not have the same ring to it does it?
The reason why the DA42 is so popular in the UAV scene is that it is powered by two diesel engines with very high fuel economy. There are reports of DA42 UAVs with 40h endurance. This is impressive for a system using a conventional (infernal combustion) propulsion system, allowing for persistence at the target.
The beer? Well if it is a "Sink the Bismarc", then it can probably be used to fuel the DA42...
A bug or a feature?
Some cheaper Li based batteries get a SUBSTANTIALLY lower lifespan (factor 10 or worse) if they are regularly discharged below 50%. It may very well be that what we see here is the properties of a bad battery being sold as a "feature". Not something you want to give your customers regular access to.
All aircraft are built to an order.
Any manufacturer that builds aircraft in the hope that it will be sold has serious problems.
The article says "the world’s first commercially available electric aircraft.". The Antares 20E fulfilled this description 6 years ago. Whether the aircraft mentioned in the article will be built in the numbers of the Antares still remains to be seen. There is a vast gap between a flying prototype and a press release and a series production aircraft.
Mine's the one with a 11 kWh battery in the pocket.
Please perform your research before publishing
The first electric aircraft to be commercially available was the Antares 20E.
First flight was in the summer of 2003.
See http://lange-aviation.com/htm/english/products/antares_20e/antares_20E.html for further details.
The alternative route
Or go the alternative route:
Skip the troublesome Ares solution and reuse the proven shuttle components:
This is at least what a number of NASA Ares engineers believe in and work on in their spare time.
Cheaper, Faster, Lower technical risk.
No mammoth launcher like the Saturn V
Mine is the one with a slide ruler in the pocket
"Laptop battery tech" is simply a completely wrong description. Without further research I would guess that the cells used will be similar to these: http://saftbatteries.com/Produit_Large_VLM_cell_range_301_62/Default.aspx
These are high performance industrial cells which cannot be compared to the (China made) cells which can be found in laptops, electronical gadgets, or model aviation.
Which is why real aviation goes in a similar direction:
The real value of Prius
In my eyes, the real value of the Toyota Prius is that it got the alternative drivetrain out of the concept cars and into the mass market. Suddenly all the car manufacturers had to come up with a similar or (,and here is the good part,) better product.
In my eyes, the biggest problem with most hybrid cars available right now, is that one cannot drive the first 100 km or so (to work thus) on batteries only. However, doing so would require the utilization of some really good batteries (like these http://lange-aviation.com/htm/english/products/antares_20e/battery_system.html ), and they again require a slightly more serious investment than most people are ready to make.
The good news is that prices are falling, and that the technology is moving forward.
Personally I hope that my next car can have a primarily electric drivetrain.
....A helicopter because anything is simpler than a vehicle consisting of 10.000 parts doing their best to shake apart.
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