Zephalto - Low-carbon space travel

[olivier boucher]

https://zephalto.com/en/

Zephalto is a start-up backed by the French spatial agency CNES that positions itself on low-carbon and safe "space" travel in the stratosphere at 25 km. I couldn't find what low carbon means on their web site, but I've read a French media quoting 27 t CO2eq per passenger for one trip up to 25 km (it doesn't sound that low ?!). Could this be a vehicle for delivering SO2 or some other aerosol precursor to the stratosphere? The payload must be fairly small and the cost pretty high. Smith and Wagner (2018, https://iopscience.iop.org/article/10.1088/1748-9326/aae98d) give a cost of 40,000 $/ton for balloons. It's worth a comparison: Zephalto annouces a ticket price of 5000 € per passenger. Assuming a passenger weighs 80 kg, that's about 60,000 $/ton but there is probably a huge potential for saving when scaling this up. Worth considering if low carbon and reusable ?

Olivier

[Andrew Lockley]

Costs can't be usefully calculated this way, as the crew compartment weight is likely more than that of the crew. Further, the propellant almost isn't isn't sulfur based, which would represent a large cost saving (albeit only for the final part of the flight).

Andrew 

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[olivier boucher]

sorry, I must correct myself. The French media quotes 27 kg CO2eq / passenger / flight. See
https://gazette-du-midi.fr/au-sommaire/entreprises/zephalto-toucher-presque-les-etoiles

----- Mail original -----
De: "olivier boucher" <olivier...@ipsl.fr>
À: "geoengineering" <geoengi...@googlegroups.com>
Cc: "Wake Smith" <wake...@hks.harvard.edu>
Envoyé: Mercredi 28 Décembre 2022 20:22:49
Objet: Zephalto - Low-carbon space travel