5 ms·
There are thousands of long-haul flights—and something like 100k flights overall—per day. If we're doing 10k+ rocket launches per day, then that's a huge proble
by lkbm 3y ago
There are thousands of long-haul flights—and something like 100k flights overall—per day. If we're doing 10k+ rocket launches per day, then that's a huge problem. If we're doing 1 per day, it's a rounding error. This is premature optimization.
(Either way, the solution, of course, is a carbon tax to price in the emissions.)
- flashback2199 3y agoEdit: I messed up the math - didn't see 100k per day of flights...
- wolfram74 3y agoone upside is many modern rockets use methane, synthesizing methane with pv/wind power would be much lower impact, depending on how much of the exhaust is actually at escape velocity it could be very slightly carbon negative, like new forged steel with ore prepped with clean hydrogen.
- flashback2199 3y agoCorrect me if I'm wrong but I am under the impression that Starship does not use that, the least expensive fuels for rockets are highly CO2 emitting, and the least expensive fuels are what will get rolled out in mass numbers if SpaceX, Blue Origin, and others succeed in building a rocket transportation industry.
- avhon1 3y agoStarship, Blue Origin's upcoming heavy-lift rocket New Glenn, and United Launch Alliance's upcoming heavy-lift rocket Vulcan, are all powered by methane and oxygen.
- lacksconfidence 3y agostarship uses methalox, a combination of methane and oxygen. I'm far from an expert, but my understanding is the methane comes from refining LNG.
- snewman 3y agoThat's generally where methane comes from today, but in time it may come from captured CO₂, e.g. see https://terraformindustries.com/ https://terraformindustries.com/ (disclaimer: I am a minor investor).
- cma 3y agoElon said by 2028 they will be in active passenger service replacing long haul aviation for cheaper than a business class ticket.
- LeifCarrotson 3y agoThat's not realistic simply because of the carbon requirements. Long haul aviation only burns a couple hundred kg of jet fuel per passenger. (I don't know how the top-level comment is calculating 1-3 tonnes of CO2 per passenger, Contrail effects? Construction of the plane? Altitude? Incomplete combustion? but a 250-passenger 787 doesn't carry 750,000 kg of fuel, it only fits 100,000 kg at most, plus plenty of reserve capacity). The flight only costs $100-$200 per person in fuel. Rocketry is far less efficient than a modern high-bypass turbofan. NASA can afford to buy 75,000 kg of methane per astronaut. Even if the rocket was amortized to zero over infinite flights, and had zero maintenance costs, even if crew cost nothing and airport/spaceport leases cost nothing, thermodynamics insists that you still have to buy $100,000 worth of RP-1 rocket fuel. A business class ticket cannot buy enough carbon to support 75,000 kg of emissions.
- bryanlarsen 3y agoStarship has the size to carry about 400 passengers. Both stages together carry about 5,000t of propellant. But over 3/4 of that is liquid oxygen, and most of that is the first stage. The second stage alone with 1200t of propellant can't put humans into orbit, but it does have a range comparable to that of a 787. So 300t of liquid methane will get 400 passengers about as far as a 787 can get 250 passengers with 100t of kerosene. A starship ticket could theoretically cost <3x the price of an airline ticket. A rocket may be less efficient than a turbofan but it gains it back by coasting through space for all but 3 minutes rather than pushing through air for the entire flight.
- pi-e-sigma 3y agoIt doesn't gain anything back, what are you on. Before landing it has to shed all the speed it gained that was needed for the ballistic trajectory. That energy is lost. Orbital or suborbital flights will never, ever be competitive to flying with regards to required energy expended.
- flashback2199 3y agoJust as 100k jet airplane flights per day would have been unimaginable in the ~50s when the jet airliner industry started, I actually can imagine a near future where many more than 10k rockets per day are launched, if the industry has it's way and succeeds in reducing costs dramatically.
- m4rtink 3y agoAt such scale it would be a different (and in some cases potentially much more dangerous :D) technology - huge hydrolox SSTOs, launch loops, rotovators, nuclear lightbulb SSTOs, maybe even orbital elevators.