Comment by CRUDite | Hacker News Reader

Comment by CRUDite | Hacker News Reader

Apart from the Aerion as2 i dont think there are many other credible supersonic aircraft in development other than the Nasa one. Concorde, other than the booms, had engines so loud, and i mean insanely loud they would not be popular these days. I remember covering my ears as it flew overhead.

I do find Elon Musks frequent mentions of a vtol ss aircraft quite interesting. Electric engines would not have the same issues at high altitude as conventional ones. Battery density is starting to get in the right area to make this feasible.

He is frequently distainful of flying cars but one logical conclusion of this is indeed potentially flying cars (Tesla secret projects anyone?). When you think about how much of the world is inaccessible, one of these would make a great thunderbirds style exploration vehicle ( provided it had a large expandible solar array stowed somehow) . Fancy a trip to the Kamchatka ground zero? No problem! I wonder whether aerodynamically they would not need to be so concorde like and maybe just bullet shaped. Perhaps on Mars you could have supersonic blimps

> ... had engines so loud, and i mean insanely loud they would not be popular these days. I remember covering my ears as it flew overhead.

I lived near Heathrow and Concorde was such a thing of beauty that the noise, if anything, just added to the spectacle!

Trust me, this never got old:

https://m.youtube.com/watch?v=i1ShTUVIzCI

Haha I personally would love it, but I cannot imagine car alarms going off would be tolerated on a daily basis! Great video if thats yours. On the flip side, I think about how we have tornado siren tests every week at 3p, and my office tower is immediately adjacent to a fire station with the siren on the rooftop blasting at my window for 2 minutes a week, we have to mute conference calls and whatnot during the test... its just a part of life.. I mean, surely they could test those things every month during tornado season and be just fine.

What are the issues at high altitude? Current turbine engines can already operate efficiently at 50,000 feet or more. There's not much to gain in drag reduction at altitudes higher than that. And there are safety concerns in terms of time to descend in case of loss of cabin pressure.

Boom's XB-1 demonstrator fabrication is well underway: https://www.linkedin.com/posts/boom-technology-inc%2E_avgeek.... They're very legit, hiring tons of people from Scaled, SpaceX, Lockheed etc.

Yeah, Boom is quite credible.

Buoyant forces in the Martian atmosphere would be teeny tiny no? I don’t think blimps would work very well.

You could maybe get some sort of inflatable lifting body to work at high speeds though.

An advantage you have is that you can fill them with hydrogen and be fine, since there's no oxygen to allow them to suddenly combust

Which you would then do what with, as there's no free supply of oxygen to burn it with in the engine?

You would use the hydrogen in gaseous form to reduce the net weight of the aircraft to be lighter than the surrounding atmosphere (hydrogen gas has an extremely low density). This enables the craft to float without having to burn fuel just to stay aloft.

https://en.wikipedia.org/wiki/Airship

> Electric engines would not have the same issues at high altitude as conventional ones

Some of them they still do. Their air is still less dense, so if you force the same volume out per second, you generate less thrust anyways cause there is less mass per volume (and thus less thrust for you)

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