Carnival of Space 633

The Carnival of Space 633 is up at Cosmoquest.

Universe Today – NASA is Working on Electric Airplanes

NASA, GE and other companies are developing electric aircraft, which could start replacing commercial jets by 2035.

NASA is investigating cutting-edge material science to create lighter and smaller electronics. To this end, they recently signed a $12 million contract with General Electric (GE), one of the world leaders in the development of cutting-edge silicon carbide (SiC) technology.

Semiconducting mineral is used in the fabrication of high-temperature, high-voltage electronics, and GE is hoping to use it to meet the size, power, and efficiency requirements specified by NASA. These specifications call for an inverter that is no larger than a suitcase and capable of generating a megawatt (MWs) of electricity.

NASA’s Single-aisle Turboelectric Aircraft with an Aft Boundary-Layer (STARC-ABL) uses advanced propulsion technologies. It needs 2.4 MW of power to operate.

Universe Today – NASA is Going to Test 25 New Technologies in Upcoming Aircraft, Balloon and Sub-Orbital Rocket Flights

In 2017, the MOJO Micro-robot was one of the chosen technologies in the Tech Flights program. It was designed to traverse 3D structures like space habitats built in space. The MOJO Micro-robot was developed by MIT for construction and inspection of structures. Image Credit: MIT’s Center for Bits and Atoms

30 thoughts on “Carnival of Space 633”

  1. Hydrogen fuel cells address a lot of the issues with electric planes.

    1. (1) As the energy requirement grows relative to the system size, a fuel tank (even a double insulated liquid H2 tank) ends up much cheaper than a battery of the same stored energy.
    2. (2) Much lighter too.
    3. (3) H2 fuel cells have the advantage of losing weight as the energy is used. And the product is just water so throw that over the side.
    4. (4) Refuelling with liquid H2 can proceed at a high rate, much faster than battery recharge.

    There are still some problems that need addressing
    (1) Liquid H2 is not something that standard airports are set up to deal with.
    (2) Liquid H2 is very light (good) but it occupies very large volumes (bad). You’ll need to dedicate a significant slab of your fuselage to large insulated tanks.
    (3) H2 fuel cells of the required (multi-megawatt) power are still not small, light and cheap.

  2. Lithium air is totally unrealistic. The best bet is lithium sulfur, if they manage to get a solid electrolyte preventing dendrites. And even those have issues with cycling due to the extremely low solubility of Li2S.

  3. Well, yes, but now that you ask, burn it perhaps. Seems like everything is going H in cars and trucks, so why not airplanes? Even fuel cells have smallish battery pack to buffer the load, like a hybrid, but the O is there in the atmos, as with cars. An innocent question!

  4. fuel cost is only a very small part of the airticket (less than 5%

    The particular cost breakdown you’ve linked to is a very short haul flight where the actual flying part is a small fraction of the total cost.

    As flights get longer the fuel becomes a much more important part of the equation.

  5. I first saw the weight increase of lithium-air batteries pointed out here, in the appendix. Interesting article on how to run an industrial society without fossil fuels.
    Here he gives the details on why wind & solar can do little to solve the problem.
    The author has more doubts about the reality of Global Warming than I consider justified, but his position is he doesn’t care whether it is true we need to get off fossil fuels because of limited supply anyway. Also getting off FF now where it is easy will give us more time to find alternatives for where it is hard.

  6. Yes…

    1 kg × 42 MJ/kg × 33⅓% Carnot Efficiency = 3.9 kWh/kg for JP-A
    3.9 kWh/kg … ÷ 13 = 0.30 kWhkg for “modern batteries” using that calc.

    The 85 kWh Tesla battery weighs over 540 kg. 
    85 ÷ 540 = 0.157 kWh/kg … fully packaged. 

    People wishing to criticize this calculation should also remember that the Tesla 85 kWh battery is “fully packaged, fully road-worthy”, having double-redundant weather sealing, having heat wicking tech, having heavy bus-bars to conduct the high power into and out of the module. That is … necessarily … part of the packaging overhead.  

    This is why eve 13-to–1 is probably pretty optimistic. 

    But no matter, one can also derate jet fuel by considering its “packaging”, tanks, pipes, hoses, pumps, valves, fill-gas systems, fire control systems, redundancy. Right?

    GoatGuy ✓

  7. You know, I didn’t think of that.  And yes, you are right. Perhaps tho’, like jet fuel, the average is better than the starting mass of both-oxidizer-and-reductant type lithium-ion batteries. Which have to carry both either when charged or discharged.  

    I just wonder what real, tight, safe, compact, powerful, relatively inexpensive ‘numbers’ might be developed. Musk seems to think that 1+ kWh/kg is doable. One wonders about the safety. Others have projected numbers as high as 4 kWh/kg … usually by loudly ballyhooing just one anode, either anode or cathode technology, but not both in the context of {+electrolyte & packaging}.  Which ruins the numbers.  

    Still, if something north of 2 kWh/kg is feasible, then I think that long-regional air-travel by electric plane may well be possible. The numbers work out OK for that, easily. Without relying on magical airframe pusher-prop technology, nor below-expected-speed transport.  

    I’m personally betting on some kind of super-hybrid though. Turns out that jet-turbine engines can be made WAY more efficient at particular, high, output power levels. So, having smaller jet engines, just “amped up” with powerful hybrid motor-generators and modestly substantial battery packs, might be the calculus-optimum.  

    Not my professional domain.
    GoatGuy ✓

  8. By Tesla style you mean much less likely to burn than any gasoline powered car I assume, because that’s the fact.

  9. “the fact that battery mass remains a constant over the entire flight is a significant difference from petrol-powered flight”
    & while the lithium-air batteries *potentially* have much higher energy density than other batteries, they have the complication that they get heavier as they discharge.

  10. Batteries will need a whole lot better power densities than they have now. One kg of jet fuel has the energy of about 13 kg of modern batteries.

  11. … Have we not discussed this already? 
    → → yes

    … difficult [but possible] technically [with today’s] battery cells.
    → → yes, for short-and-slow comporting

    … Of course, given that jet fuel is cheap 
    → → no. $1.92/gallon, delivered. 

    … and that the fuel cost is only a very small part of the airticket (less than 5%, [1]), 
    → → no, more like 60% or more for long-haul flights

    … Just the interest [payment] on the batteries would be far greater than fuel cost for an airplane of today…
    → → on this we AGREE. Yep.

    The real issue (if ‘fuel/energy’ cost) is that present day jet fuel at $1.92/gallon delivers aeronautical energy at about 7¢/kWh.  

    $1.92 per gallon.
    0.800 kg/L
    42 MJ/kg
    33⅓% thermodynamic efficiency…


    And if a plane going only 2,000 km, at only 75% of jet-speed (saving 50% of energy, with right wings) then

    0.188 kWh/passenger-nm • ( 1 km = 0.547 nm ) = 0.103 kWh/passenger-km

    100 passengers
    2,000 km
    0.103 kWh/p-km
    50% energy savings, going slower…
    10,350 kWh
    0.8 kWh/kg for MAGIC batteries

    → 12,904 kg battery
    divide by 100 passengers…
    130 kg batteries per passenger. 

    just wow…

    GoatGuy ✓

  12. Nothing can go wrong with this idea. After we have the first plane burn down Tesla-style, nobody will want to get on one.

  13. Have we not discussed this already? Yes, jet fuel is much better from a technical point of view for airtravel. Yes, jet fuel allows far longer range.

    But, as far as I remember, an airliner with a fairly short range (2000 km) and a slightly lower air speed (650 km/h versus 800 km/h) was possible, albeit very difficult from a technical point of view with to days battery cells.

    Of course, given that jet fuel is cheap and that the fuel cost is only a very small part of the airticket (less than 5%, [1]), then battery powered flight does not make any sense economically. Just the interest on the batteries would be far, far greater than the actual fuel cost for an airplane of today…


  14. Hmmm, wouldn’t service and maximum ceilings be significantly affected as well? Since the batteries don’t lose weight like jet fuel during a flight, the electric aircraft never gains in efficiency, or ability to fly higher. Let alone, an electric aircraft doesn’t have the thrust from the high energy core of jet engines to help at altitude. But then, the electric aircraft doesn’t have to work about oxygen starvation to the powerplant, either. Be interesting to see what NASA comes up with.

  15. PS… A 767 holds 90,770ℓ of jet fuel, 0.8 kg/L = 72,600 kg, times 3.9 kWh/kg = 283,000 kWh of aeronautical motive power at 33⅓% jet turbine-to-thrust efficiency.

    300 seats, 5,000 nautical miles), → 0.188 kWh/person-nm.

    If we just take … the lithium battery tech of today (over 0.45 kWh/kg), then wave our magic unicorn-horn wand and project 1.2 kWh/kg prismatic cells, with 0.8 kWh/kg SAFE packaged, SAFE thermal cooling etc., future … and we admit that there are going to be no jaw-dropping efficiencies in subsonic airframe tweaking, then taking the 0.188 kWh/person-nm figure, for a smaller craft (150 passengers), with a shorter flight profile (1,500 nm), then we get what … 

    150 × 1,500 × 0.188 → 42,480 kWh of battery needed.  
    Divide by 0.8 kWh/kg → 53,100 kg of battery, cooling, etc. 

    Its definitely worth reading … https:\en.wikipedia.orgwikiFuel_economy_in_aircraft (repl with slash)  

    Especially the graph of a 737–200 showing minimum specific fuel at about 2,500 nm range (i.e. without FULL tanks).

    The napkin prediction is that 53 tons of battery to go only 1,500 nautical miles – even if the all-electric gambit offers amazing efficiency — is still going to lose to jet fuel from energy density, and the non-loss-of-mass of batteries in flight.

    Just saying, folks. 
    Great talking points.
    Nothing ‘radical new discovery’ tech on horizon.

    GoatGuy ✓

  16. Yah… electric flight!  

    Jim Baerg sez it well … mass of batteries. It pretty much is the ‘whole problem’ in a nutshell. Opinions vary, but for sure … the fact that battery mass remains a constant over the entire flight is a significant difference from petrol-powered flight, where the fuel mass is gradually being reduced.  

    Even at turbine thermodynamic efficiencies of “only” 33⅓%, the 42 MJ/kg thermal, 14 MJ/kg motive power (3.9 kWh/kg) of jet fuel is pretty impressive compared to SAFE-packaged battery tech. SAFE in caps because if there’s one thing the FAA certifications will demand, is absolutely, positively, 200% overdesigned safety packaging for highly flammable lithium-ion-or-air batteries. They can NOT catch fire, period. In flight or otherwise.  

    This requirement imposes mass overhead of its own. Active non-ionic (electrically insulating) liquid cooling of the cell-packs. Radiators. Redundant DC-to-AC power inverters. Active cooling of…  

    Then there’s the battery-swap tech(no way to recharge in short time, many megawatt-hours) again … needing to be 6-nines safe. More Mass. Connector wear-and-tear. Wow. Just wow.

    Just Saying,
    GoatGuy ✓

  17. For electric airplanes the crucial thing is high energy density batteries. Lithium-Air is the most plausible tech for that. Cutting the weight of everything else is just a modest gain compared to cutting the weight of the battery.

  18. What? Surely using the motors as generators at the front to power the back fan generates more drag than it reduces? Why not just run the rear fan on the same electric power? I get using ‘regenerative braking’ when dropping in altitude, but that’s bizarre to say it’s wholly powered by drag.

  19. Looks to me like a hybrid jet… Both engines under the wings are proper jets, reduced in size thanks to the chaparral-style fan doing its boundary-layer thing in the back…

  20. All the eVTOL work is helping to push some work on high power low weight electronics and inverters. STARC-ABL in particular is trying to do a full up “ironbird” test run on the ground for a complete airliner sized system, as opposed to all those Uber UAM eVTOL rigs. EU is doing a lot of relevant work regarding combined propulsion/electric work as well for the airliner design space (The ULTIMATE project doing lots of weird stuff like box rotor open rotor engines, liquid metal recuperators, and a funky turbo-piston compound like the turbocompound diesel engines of old)

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