Not seeing the connection. Somebody's going to be launching satellites either way, whether it's SpaceX or a competitor.
Not that I am at all opposed to more satellite launches, but... how can you possibly believe that SpaceX increasing the global supply of (relatively) cheap rocket launches won't affect the quantity of stuff launched into orbit?
This is like, economics 101 - when supply goes up and prices go down, demand increases in response.
That said, I think batteries become viable, if not today, maybe soon:
Very possibly, although I should point out that experimental "10x" improvements have been announced about 3 times per year (on Slashdot, no less), every year, for at least the past decade. And yet, batteries today are still not even 10x better than batteries were then - let alone 10^30 times better...
Your point about jet fuel expenditure being front loaded on the trip... I read somewhere that the most fuel efficient flight for a jet is around 4300 miles. It seems that an alternate fuel for short hops could make sense.
Don't bet on it.
For short hops, efficiency may be maximized with a lower cruising altitude and speed, which in turn allows the use less wing sweep and higher bypass ratio engines. But, whether you want a turboprop like a C-130, or a turboramjet like the SR-71, the best fuel is still some kind of diesel.
Growing crops to turn into fuel, it amounts to an *extremely* inefficient solar solution (months of solar collected in the form of plant biomass) which then has to be processed into fuel... better perhaps to take those fields grow food in them, and throw up panels in the deserts to charge batteries.
Current bio-diesel and (to a lesser extent) bio-ethanol schemes are very wasteful. But, from what I have read I think that algae-derived bio-diesel and cellulosic ethanol both have the potential to be truly energy positive, without directly competing with food crops for land.
Indeed, breakthroughs have been announced about 3 times a year (on Slashdot no less), every year, for the past decade straight. Surely it will all come to fruition any day now, right?;-)
Regardless, there is always the more boring solution of the Fischer-Tropsch process, which has already been proven to be viable on a large scale in the past. The only reason it (or some modern successor) is not used much at the moment, is because it so much cheaper to just pump oil out of the ground.
As for your comments about the charging issues, I imagine a battery swap solution being viable for fleets of aircraft.
Not with current technology - at least, not in a business sense. See my comment above.
Airports would potentially be the sort of scenario where exchanging the batteries themselves between flights might be feasible.
A battery for a battery-powered 777 would store about 17 MWh - maybe enough for a 30 minute flight - weigh about 100 tons, and cost about $2,000,000.
To operate continuously, you need to be able to do a full recharge in about an hour (a plane flying such short routes spends most of its time on the ground, but you can bet that swapping two 100 ton pieces of equipment won't be instantaneous, either). That means the airport will need to be able to supply 17 MW of power per operational plane.
(If you don't want to charge an individual battery that fast, you can buy a bunch of extra $2,000,000 batteries. But, you still need to recharge the collection at an average rate of about 17MW per operational plane, otherwise you'll soon run out of fully charged spares.)
The LAX airport has hundreds of large jets arrive each day, most of which, I'm sure, flew a lot longer than 30 minutes to get there, and consumed proportionally more energy in the process. If each of these required a such a battery swap, the airport would require the continuous output of several dedicated full-size (1 GW) nuclear power plants.
One more thought, following up on my other answer above...
3% of the energy also means 3% of the flight time, all else being equal.
A real Boeing 777 can stay aloft for about 17 hours before it runs out of fuel.
A hypothetical Tesla 777 could stay aloft for about 30 minutes before it ran out of juice.
I can't imagine that either the FAA or any commercial airline would be excited about operating a plane that will lose engine power every time there is a mere 10 minute delay in getting permission from the tower to land.
An electric plane would have about 3% of the energy to work with, and little-to-no efficiency gains compared to a hydrocarbon-powered jet.
A Boeing 777-200LR (among the longest-range airplanes ever built) can fly almost 18,000 km with a full load. Multiply this by 3%, and we get 540 km, or 290 nmi. (And that's a huge airplane; smaller planes generally have much shorter range, assuming they're actually carrying a payload.)
However, this may actually be an over-estimate of the electric plane's range, though, because a significant portion of the 777's fuel is devoted to take-off and climbing to cruising altitude right at the beginning of the flight. You can select a lower cruising altitude to avoid some of this, but you'll have to fly slower to maintain comparable range in the thicker air.
Los Angeles to Las Vegas is probably doable.
Paris to Madrid is way too far.
London to Frankfurt or Sydney to Melbourne is a stretch; either would probably require reductions in payload and/or cruising speed.
And of course, even where the route is possible, this is a horrifically expensive way to go about things: you need a humongous plane to go much of anywhere (at least if you want it to be faster than ground transport), which will be both time consuming and dangerous to recharge (kilovolts and kiloamps at the same time if you want to make multiple flights per day) after every short hop.
All around, it makes far, far more sense to just use liquid fuels. Synthetic fuels are a legitimate option, although many of the specific options commonly suggested are a poor fit for aviation:
Hydrogen is a terrible choice unless you're planning to go hypersonic, or into space. Its density is way too low, even liquefied, and you'll have to work with extreme temperatures, pressures, or both - which means heavy tanks and significant safety challenges.
Methane is good for ground transport or rockets, but it's too hard to liquefy to be a good choice for ordinary subsonic planes, I think.
Amonia (which someone else suggested) is an interesting possibility for rockets, but way too toxic for me to be comfortable fueling every airliner with 50+ tons of the stuff.
Ethanol is a legitimate option. (But please, stop making it out of corn!)
Really, though, the best known fuel for planes is the one we're already using: a diesel-type hydrocarbon blend. It's energetic, dense, not particularly explosive or flammable, stable across a wide temperature range (especially the higher grade stuff available to aviation users), and fairly clean-burning in a modern turbine.
It's also dirt cheap, thanks to oil wells. If you want to replace fossil fuels in jets, figure out how to make synthetic diesel cheaply. Bio-diesel seems promising, but at the moment it's really expensive, and the manufacturing process doesn't scale up enough.
Lots of flights are between New York and Chicago, LA and Las Vegas, Miami and New York, Seattle and LA... their is no necessity that that electrics have to do trans-pacific runs before we can start using them.
Of those, only Los Angeles to Las Vegas is remotely feasible with something like a Li-Ion powered passenger "jet"; all the other routes you mentioned are long enough that you would either have to go really slow, cut the payload down to nothing, make stops along the way to recharge, or some combination thereof.
A full sedan-sized gas tank is about 55 kg, and comprises 4% of the weight of the whole car.
The Tesla Model S battery pack is 540 kg, and comprises 28% of the weight of the whole car.
A fully-fueled long-haul passenger jet may be as much as 50% fuel by weight.
There is simply no weight margin available to devote to multiplying the weight of the energy storage system by 10x; attempting to do so leaves you with something too heavy to fly at all.
Moreover, even if it could get off the ground, a miraculous all-electric plane that was 100% battery by weight would still lack the energy required to carry the weight of the battery, alone, at 600 mph across the Atlantic Ocean using wings and ducted fans. (This assumes present-day resuable battery tech; I am not suggesting that future battery tech couldn't do better.)
Additionally, most of the factors that make electric cars more efficient than hydrocarbon-powered ones (like regenerative braking) don't really apply to airplanes.
A typical gas-powered sedan's fuel tank may hold around 15 U.S. gallons of gasoline, which weighs about 40 kg. The tank itself may add another 10 or 20 kg, for a total of ~55 kg. In contrast, the battery pack of the Tesla model S weighs 540 kg! - even though its range is still a bit less.
This 10x weight increase is acceptable in a sedan, because the gas-powered sedan already weighed about 1400 kg; adding another ~500 kg is significant, but not overwhelming.
For a typical airplane, though, increasing the weight of the energy source by 10x guarantees that it will never leave the ground: at take-off the jet fuel powered version is already 25-60% fuel by mass; increasing this by 10x would increase the total mass of the plane by 3-6x.
Realistically, a hypothetical "Tesla 777" could not afford to devote meaningfully more mass to energy storage than the equivalent Boeing jet does. So, whereas the sedan can store about 25% of the energy available to its competitor, an electric jet would have only 3% to work with.
Moreover, while the sedan can make up for some of its energy shortage by a combination of (1) regenerative braking, (2) vastly more efficient idling, and (3) improved aerodynamics, an electric jet would not enjoy such advantages:
1) Regenerative braking is useless for long-haul plane flights, because the optimum flight profile does not involve slowing down until it is time to land, at which point additional energy is not normally needed.
2) Similarly, the ability of electric drive systems to idle efficiently is not helpful because a good flight plan does not idles the engines at any time, except the landing approach.
3) Unlike many gas-powered cars, modern turbine-powered planes are already aggressively optimized for aerodynamic efficiency (as opposed to looks). An electric plane would not enjoy any inherent advantage here.
Sometimes people will suggest solar panels as the solution but - even ignoring all the other problems with this idea - there simply isn't enough surface area on a high-speed airplane to collect enough sunlight to meaningfully offset the drain from the engines:
The 777 has a wing area of around 400 m2, implying that even if the entire surface of the aircraft (fuselage included) were covered in 100% efficient solar panels, no more than 1 MW could be collected. But, the 777's engines can each produce something like 40 MW of power (at full throttle and low altitude).
Of course they're producing less than that during cruise - but not 80x less.
Slashdot Mirror
Not seeing the connection. Somebody's going to be launching satellites either way, whether it's SpaceX or a competitor.
Not that I am at all opposed to more satellite launches, but... how can you possibly believe that SpaceX increasing the global supply of (relatively) cheap rocket launches won't affect the quantity of stuff launched into orbit?
This is like, economics 101 - when supply goes up and prices go down, demand increases in response.
That said, I think batteries become viable, if not today, maybe soon:
Very possibly, although I should point out that experimental "10x" improvements have been announced about 3 times per year (on Slashdot, no less), every year, for at least the past decade. And yet, batteries today are still not even 10x better than batteries were then - let alone 10^30 times better...
Your point about jet fuel expenditure being front loaded on the trip ... I read somewhere that the most fuel efficient flight for a jet is around 4300 miles. It seems that an alternate fuel for short hops could make sense.
Don't bet on it.
For short hops, efficiency may be maximized with a lower cruising altitude and speed, which in turn allows the use less wing sweep and higher bypass ratio engines. But, whether you want a turboprop like a C-130, or a turboramjet like the SR-71, the best fuel is still some kind of diesel.
Growing crops to turn into fuel, it amounts to an *extremely* inefficient solar solution (months of solar collected in the form of plant biomass) which then has to be processed into fuel... better perhaps to take those fields grow food in them, and throw up panels in the deserts to charge batteries.
Current bio-diesel and (to a lesser extent) bio-ethanol schemes are very wasteful. But, from what I have read I think that algae-derived bio-diesel and cellulosic ethanol both have the potential to be truly energy positive, without directly competing with food crops for land.
Indeed, breakthroughs have been announced about 3 times a year (on Slashdot no less), every year, for the past decade straight. Surely it will all come to fruition any day now, right? ;-)
Regardless, there is always the more boring solution of the Fischer-Tropsch process, which has already been proven to be viable on a large scale in the past. The only reason it (or some modern successor) is not used much at the moment, is because it so much cheaper to just pump oil out of the ground.
As for your comments about the charging issues, I imagine a battery swap solution being viable for fleets of aircraft.
Not with current technology - at least, not in a business sense. See my comment above.
Airports would potentially be the sort of scenario where exchanging the batteries themselves between flights might be feasible.
A battery for a battery-powered 777 would store about 17 MWh - maybe enough for a 30 minute flight - weigh about 100 tons, and cost about $2,000,000.
To operate continuously, you need to be able to do a full recharge in about an hour (a plane flying such short routes spends most of its time on the ground, but you can bet that swapping two 100 ton pieces of equipment won't be instantaneous, either). That means the airport will need to be able to supply 17 MW of power per operational plane.
(If you don't want to charge an individual battery that fast, you can buy a bunch of extra $2,000,000 batteries. But, you still need to recharge the collection at an average rate of about 17MW per operational plane, otherwise you'll soon run out of fully charged spares.)
The LAX airport has hundreds of large jets arrive each day, most of which, I'm sure, flew a lot longer than 30 minutes to get there, and consumed proportionally more energy in the process. If each of these required a such a battery swap, the airport would require the continuous output of several dedicated full-size (1 GW) nuclear power plants.
One more thought, following up on my other answer above...
3% of the energy also means 3% of the flight time, all else being equal.
A real Boeing 777 can stay aloft for about 17 hours before it runs out of fuel.
A hypothetical Tesla 777 could stay aloft for about 30 minutes before it ran out of juice.
I can't imagine that either the FAA or any commercial airline would be excited about operating a plane that will lose engine power every time there is a mere 10 minute delay in getting permission from the tower to land.
An electric plane would have about 3% of the energy to work with, and little-to-no efficiency gains compared to a hydrocarbon-powered jet.
A Boeing 777-200LR (among the longest-range airplanes ever built) can fly almost 18,000 km with a full load. Multiply this by 3%, and we get 540 km, or 290 nmi. (And that's a huge airplane; smaller planes generally have much shorter range, assuming they're actually carrying a payload.)
However, this may actually be an over-estimate of the electric plane's range, though, because a significant portion of the 777's fuel is devoted to take-off and climbing to cruising altitude right at the beginning of the flight. You can select a lower cruising altitude to avoid some of this, but you'll have to fly slower to maintain comparable range in the thicker air.
Los Angeles to Las Vegas is probably doable.
Paris to Madrid is way too far.
London to Frankfurt or Sydney to Melbourne is a stretch; either would probably require reductions in payload and/or cruising speed.
And of course, even where the route is possible, this is a horrifically expensive way to go about things: you need a humongous plane to go much of anywhere (at least if you want it to be faster than ground transport), which will be both time consuming and dangerous to recharge (kilovolts and kiloamps at the same time if you want to make multiple flights per day) after every short hop.
All around, it makes far, far more sense to just use liquid fuels. Synthetic fuels are a legitimate option, although many of the specific options commonly suggested are a poor fit for aviation:
Hydrogen is a terrible choice unless you're planning to go hypersonic, or into space. Its density is way too low, even liquefied, and you'll have to work with extreme temperatures, pressures, or both - which means heavy tanks and significant safety challenges.
Methane is good for ground transport or rockets, but it's too hard to liquefy to be a good choice for ordinary subsonic planes, I think.
Amonia (which someone else suggested) is an interesting possibility for rockets, but way too toxic for me to be comfortable fueling every airliner with 50+ tons of the stuff.
Ethanol is a legitimate option. (But please, stop making it out of corn!)
Really, though, the best known fuel for planes is the one we're already using: a diesel-type hydrocarbon blend. It's energetic, dense, not particularly explosive or flammable, stable across a wide temperature range (especially the higher grade stuff available to aviation users), and fairly clean-burning in a modern turbine.
It's also dirt cheap, thanks to oil wells. If you want to replace fossil fuels in jets, figure out how to make synthetic diesel cheaply. Bio-diesel seems promising, but at the moment it's really expensive, and the manufacturing process doesn't scale up enough.
Lots of flights are between New York and Chicago, LA and Las Vegas, Miami and New York, Seattle and LA... their is no necessity that that electrics have to do trans-pacific runs before we can start using them.
Of those, only Los Angeles to Las Vegas is remotely feasible with something like a Li-Ion powered passenger "jet"; all the other routes you mentioned are long enough that you would either have to go really slow, cut the payload down to nothing, make stops along the way to recharge, or some combination thereof.
Airplanes are not cars.
A full sedan-sized gas tank is about 55 kg, and comprises 4% of the weight of the whole car.
The Tesla Model S battery pack is 540 kg, and comprises 28% of the weight of the whole car.
A fully-fueled long-haul passenger jet may be as much as 50% fuel by weight.
There is simply no weight margin available to devote to multiplying the weight of the energy storage system by 10x; attempting to do so leaves you with something too heavy to fly at all.
Moreover, even if it could get off the ground, a miraculous all-electric plane that was 100% battery by weight would still lack the energy required to carry the weight of the battery, alone, at 600 mph across the Atlantic Ocean using wings and ducted fans. (This assumes present-day resuable battery tech; I am not suggesting that future battery tech couldn't do better.)
Additionally, most of the factors that make electric cars more efficient than hydrocarbon-powered ones (like regenerative braking) don't really apply to airplanes.
I know what a ram air turbine is. What relevance does this have to the viability of large electric airplanes?
Here's the real answer:
A typical gas-powered sedan's fuel tank may hold around 15 U.S. gallons of gasoline, which weighs about 40 kg. The tank itself may add another 10 or 20 kg, for a total of ~55 kg. In contrast, the battery pack of the Tesla model S weighs 540 kg! - even though its range is still a bit less.
This 10x weight increase is acceptable in a sedan, because the gas-powered sedan already weighed about 1400 kg; adding another ~500 kg is significant, but not overwhelming.
For a typical airplane, though, increasing the weight of the energy source by 10x guarantees that it will never leave the ground: at take-off the jet fuel powered version is already 25-60% fuel by mass; increasing this by 10x would increase the total mass of the plane by 3-6x.
Realistically, a hypothetical "Tesla 777" could not afford to devote meaningfully more mass to energy storage than the equivalent Boeing jet does. So, whereas the sedan can store about 25% of the energy available to its competitor, an electric jet would have only 3% to work with.
Moreover, while the sedan can make up for some of its energy shortage by a combination of (1) regenerative braking, (2) vastly more efficient idling, and (3) improved aerodynamics, an electric jet would not enjoy such advantages:
1) Regenerative braking is useless for long-haul plane flights, because the optimum flight profile does not involve slowing down until it is time to land, at which point additional energy is not normally needed.
2) Similarly, the ability of electric drive systems to idle efficiently is not helpful because a good flight plan does not idles the engines at any time, except the landing approach.
3) Unlike many gas-powered cars, modern turbine-powered planes are already aggressively optimized for aerodynamic efficiency (as opposed to looks). An electric plane would not enjoy any inherent advantage here.
Sometimes people will suggest solar panels as the solution but - even ignoring all the other problems with this idea - there simply isn't enough surface area on a high-speed airplane to collect enough sunlight to meaningfully offset the drain from the engines:
The 777 has a wing area of around 400 m2, implying that even if the entire surface of the aircraft (fuselage included) were covered in 100% efficient solar panels, no more than 1 MW could be collected. But, the 777's engines can each produce something like 40 MW of power (at full throttle and low altitude).
Of course they're producing less than that during cruise - but not 80x less.