21–30 of 47 posts
How does water vapor last longer at 25km than at 33km? From 33km it has to pass through the lower altitude which would mean more time than vapor that started at 25.
2. It may be of a different constitution by the time it hits 25 km (larger droplets drop faster; extreme example: hail), giving it a higher terminal velocity.
(I don't know whether any of these is true)
The biggest challenge will the same thing that killed Concorde: finding customers to pay super prices for super speed.
My recollection is that noise regulations and landing rights to landlocked cities in the US killed Concorde. Not seat prices.
I admit, I was a little disappointed to find no mention of Skylon, even if it's at an earlier stage of development than some of these other contenders. The SABRE engine appears to be coming along well, with one of the largest challenges - cooling the incoming air extremely rapidly - seemingly overcome. http://www.reactionengines.co.uk/sabre_howworks.html
As the energy cost of high speed travel goes up with the square of the velocity, it'd be a whole lot cheaper to stick to subsonic travel in business class -- lie-flat beds, in-flight showers, and broadband. How many people are willing to pay $10,000+ to save 10-15 hours on the flight time from LHR-SYD or LAX-Tokyo? Especially when the accommodation during hypersonic flight is going to be cramped and spartan due to weight constraints (and it's still going to involve security theater at the gate and waiting hours for a scheduled departure time to roll round)?
I can believe in Aerion's supersonic Mach 1.5 bizjet -- the core market is CEOs wanting to bounce over to the opposite coast of the USA and back for a meeting within the same working day -- but I just don't believe there's going to be a mass market for hypersonic antipodeal travel on a commercial scheduled service.
The biggest challenge will the same thing that killed Concorde: finding customers to pay super prices for super speed.
Sonic booms are a not-insignificant problem as well. We've been pouring money and research into it for decades and we have barely made a dent in it. The only known shape which produces no sonic boom (Busemann's Biplane) also produces no lift. There is a known shape called the Sears-Haack body which produces very little turbulence - basically it's like a very long pointed football. The best we have been able to do is…
"This thoroughbred airliner could fly from London to Sydney in 17 hours, three minutes and 45 seconds; compared to around 22 hours on a Boeing 747." This sounds wrong - the concorde's cruising speed was more than double that of a 747. Unless they're taking the refueling time into account (Concorde would need more refueling stops)
Short legs.
The biggest challenge will the same thing that killed Concorde: finding customers to pay super prices for super speed.
Sonic booms are a not-insignificant problem as well. We've been pouring money and research into it for decades and we have barely made a dent in it. The only known shape which produces no sonic boom (Busemann's Biplane) also produces no lift. There is a known shape called the Sears-Haack body which produces very little turbulence - basically it's like a very long pointed football. The best we have been able to do is…
So if we optimize for supersonic flight it won't be so good for transonic and vice-versa... I agree with you in that probably there's no way to passively eliminate sonic booms, maybe some kind of "active" solutions, but the weight problem strikes again.
Also, I don't know if a rocket can be made without boom, as the transition in the nozzle is abrupt. Maybe it's time to review those aerospikes!
Last time I flew trans-Atlantic -- last month -- in-flight wifi with mid-ocean coverage was available for $30. And we've got Facebook, SpaceX, et al promising us all clusters of satellites delivering broadband everywhere on the planet within 5-10 years. As the energy cost of high speed travel goes up with the square of the velocity, it'd be a whole lot cheaper to stick to subsonic travel in business class -- lie-flat…
Earlier quoted context omitted.
Sonic booms are a not-insignificant problem as well. We've been pouring money and research into it for decades and we have barely made a dent in it. The only known shape which produces no sonic boom (Busemann's Biplane) also produces no lift. There is a known shape called the Sears-Haack body which produces very little turbulence - basically it's like a very long pointed football. The best we have been able to do is…
Reducing the boom is achieved by damping the pressure N-wave from the oblique shocks near the aircraft forebody. This is done in various ways but at this time we're exploring blunting the nose to increase the local air temperature which increases the local acoustic velocity and reduces the pressure jump across the shock, weakening (quieting) it.
The biggest challenge will the same thing that killed Concorde: finding customers to pay super prices for super speed.
Sonic booms are a not-insignificant problem as well. We've been pouring money and research into it for decades and we have barely made a dent in it. The only known shape which produces no sonic boom (Busemann's Biplane) also produces no lift. There is a known shape called the Sears-Haack body which produces very little turbulence - basically it's like a very long pointed football. The best we have been able to do is…
Also, at what altitudes does a boom become irrelevant? This thing will be very high so cross-continental might not be an issue either.