(01-16-2017, 01:13 PM)SomeGuy Wrote:

Warren Dew Wrote:Supersonic flight is not inherently less fuel efficient on a per mile basis, just on a per hour basis.

Yes, it is.  Fuel use is largely a function drag, and drag is a function of speed.  In addition, the drag coefficient increases significantly after about Mach 0.8, pushing up fuel consumption dramatically.

It's not that it is impossible to fly past the sound barrier, I just question whether it is possible to do so cheaply.

But what would I know?

(01-16-2017, 01:13 PM)SomeGuy Wrote:

Quote:Branson has been trying to provide supersonic service for some time; he tried to buy the remaining Concordes from British Air when British Air stopped flying them when the internet bubble burst.  That's why I view this as credible.  This company is connected to his Space Ship One venture, which is less likely actually to offer paid service, but which has relevant technology.

Don't get me wrong, I think all that stuff is cool, but I wonder what technology you'd think Space Ship One has that would translate into affordable supersonic commercial jets?

Quote:

Quote:Supersonic flight is not inherently less fuel efficient on a per mile basis, just on a per hour basis.

Yes, it is.  Fuel use is largely a function drag, and drag is a function of speed.  In addition, the drag coefficient increases significantly after about Mach 0.8, pushing up fuel consumption dramatically.

It's not that it is impossible to fly past the sound barrier, I just question whether it is possible to do so cheaply.

But what would I know?

Quote:What you quoted was what I thought.  Comparative advantage held in Ricardo's day because capitalists were leery of investing abroad for fear their property being confiscated by foreign governments (e.g. investment made in imperial Russia before 1917 or American oversea capital assets that were nationalized by socialist governments after WW II). 

Quote:What I was asking about was the silly thing to which you referred.

(01-16-2017, 03:03 PM)Warren Dew Wrote:

(01-16-2017, 01:13 PM)SomeGuy Wrote:

Quote:Branson has been trying to provide supersonic service for some time; he tried to buy the remaining Concordes from British Air when British Air stopped flying them when the internet bubble burst.  That's why I view this as credible.  This company is connected to his Space Ship One venture, which is less likely actually to offer paid service, but which has relevant technology.

Don't get me wrong, I think all that stuff is cool, but I wonder what technology you'd think Space Ship One has that would translate into affordable supersonic commercial jets?

Composite materials suitable for the high temperatures of supersonic applications.

Actually this is interesting for another reason:  aerospace composites are a new technology, and Boeing already has a worldwide lead in them.  Since engineering is being done by a US team for this, it extends the US technology lead.  This is the kind of manufacturing I think the US can usefully emphasize:  emerging technologies where the US has a technical lead thanks to our strong University network.

Quote:

Quote:Supersonic flight is not inherently less fuel efficient on a per mile basis, just on a per hour basis.

Yes, it is.  Fuel use is largely a function drag, and drag is a function of speed.  In addition, the drag coefficient increases significantly after about Mach 0.8, pushing up fuel consumption dramatically.

It's not that it is impossible to fly past the sound barrier, I just question whether it is possible to do so cheaply.

But what would I know?

It's not that simple.  Drag coefficient increases substantially right at the sound barrier.  However, it then falls again at higher speeds.



If you're cruising at mach 2 or above, there's no fundamental reason why fuel economy has to be worse for supersonic flight.  There are differences due to much more research and development money being spent on optimizing engines for subsonic fuel efficiency, but that just means we ought to expect rapid improvement once fuel efficiency becomes a focus for supersonic engines.

(01-16-2017, 02:56 PM)David Horn Wrote:

(01-16-2017, 01:13 PM)SomeGuy Wrote:

Warren Dew Wrote:Supersonic flight is not inherently less fuel efficient on a per mile basis, just on a per hour basis.

Yes, it is.  Fuel use is largely a function drag, and drag is a function of speed.  In addition, the drag coefficient increases significantly after about Mach 0.8, pushing up fuel consumption dramatically.

It's not that it is impossible to fly past the sound barrier, I just question whether it is possible to do so cheaply.

But what would I know?

The only model that's even reasonably fuel efficient is the semi-ballistic model, that involves near-space flight during most of the trip.  Essentially shooting the vehicle into sub-orbit using a rail launcher, and more-or-less coasting in for a landing seems a bit extreme for all but the truly adventurous.  I don't see it, but it seems possible.

Quote:Composite materials suitable for the high temperatures of supersonic applications.

Quote:Um yeah there is.  You are showing a plot of drag coefficient CD.  Drag force is proportion to CD and speed squared. Since work is force integrated over distance, mpg would be correlated with drag force.  So even if CD returns to subsonic levels, fuel economy at 1500 mph would still be nine times less than at 500 mph.

(01-10-2017, 01:28 PM)SomeGuy Wrote: You mention comparative advantage, you might want to look up what David Ricardo actually said concerning situations where one trading partner has a consistent advantage in all or most goods, what he thought that might do to the other country, and the ridiculous thing that he thought would prevent it.

(01-16-2017, 03:20 PM)Mikebert Wrote:

(01-10-2017, 01:28 PM)SomeGuy Wrote: You mention comparative advantage, you might want to look up what David Ricardo actually said concerning situations where one trading partner has a consistent advantage in all or most goods, what he thought that might do to the other country, and the ridiculous thing that he thought would prevent it.

Here.

(01-16-2017, 03:13 PM)Mikebert Wrote:

(01-16-2017, 03:03 PM)Warren Dew Wrote:

(01-16-2017, 01:13 PM)SomeGuy Wrote:

Quote:Branson has been trying to provide supersonic service for some time; he tried to buy the remaining Concordes from British Air when British Air stopped flying them when the internet bubble burst.  That's why I view this as credible.  This company is connected to his Space Ship One venture, which is less likely actually to offer paid service, but which has relevant technology.

Don't get me wrong, I think all that stuff is cool, but I wonder what technology you'd think Space Ship One has that would translate into affordable supersonic commercial jets?

Composite materials suitable for the high temperatures of supersonic applications.

Actually this is interesting for another reason:  aerospace composites are a new technology, and Boeing already has a worldwide lead in them.  Since engineering is being done by a US team for this, it extends the US technology lead.  This is the kind of manufacturing I think the US can usefully emphasize:  emerging technologies where the US has a technical lead thanks to our strong University network.

Quote:

Quote:Supersonic flight is not inherently less fuel efficient on a per mile basis, just on a per hour basis.

Yes, it is.  Fuel use is largely a function drag, and drag is a function of speed.  In addition, the drag coefficient increases significantly after about Mach 0.8, pushing up fuel consumption dramatically.

It's not that it is impossible to fly past the sound barrier, I just question whether it is possible to do so cheaply.

But what would I know?

It's not that simple.  Drag coefficient increases substantially right at the sound barrier.  However, it then falls again at higher speeds.



If you're cruising at mach 2 or above, there's no fundamental reason why fuel economy has to be worse for supersonic flight.  There are differences due to much more research and development money being spent on optimizing engines for subsonic fuel efficiency, but that just means we ought to expect rapid improvement once fuel efficiency becomes a focus for supersonic engines.

Um yeah there is.  You are showing a plot of drag coefficient CD.  Drag force is proportion to CD and speed squared. Since work is force integrated over distance, fuel economy (i.e. work per distance) would be correlated with drag force.  So even if CD returns to its subsonic values, fuel economy at 1500 mph would still be nine times less than at 500 mph.

(01-16-2017, 03:19 PM)SomeGuy Wrote:

Quote:Composite materials suitable for the high temperatures of supersonic applications.

How would that make commercial supersonic flight cheaper?  It's already possible, has been for decades.

Quote:This is only true at constant altitude at subsonic speeds.

At supersonic speeds, the boundary layer speeds must remain subsonic due to speed of sound limitations, which changes how skin friction drag operates.

In addition, for both subsonic and supersonic speeds, higher speeds result in higher lift.  This permits aircraft to achieve adequate lift at higher altitudes where the air is thinner.  This in turn reduces drag.

Finally, at supersonic speeds, there is compressibility drag, but again, the compression wave can be used for lift.  This permits supersonic transports to cruise at much higher altitudes than subsonic transports, which again reduces drag relative to flying "in the soup".

(01-16-2017, 03:49 PM)Warren Dew Wrote:

(01-16-2017, 03:19 PM)SomeGuy Wrote:

Quote:Composite materials suitable for the high temperatures of supersonic applications.

How would that make commercial supersonic flight cheaper?  It's already possible, has been for decades.

Reduced structural weight, resulting in larger payloads or reduced fuel consumption for the same payload.  There's a reason why airlines are replacing aluminum aircraft with the composite 787.  Also, reduced need for exotic metals like titanium to withstand temperatures in key locations.

(01-16-2017, 03:54 PM)SomeGuy Wrote:

Quote:This is only true at constant altitude at subsonic speeds.

At supersonic speeds, the boundary layer speeds must remain subsonic due to speed of sound limitations, which changes how skin friction drag operates.

In addition, for both subsonic and supersonic speeds, higher speeds result in higher lift.  This permits aircraft to achieve adequate lift at higher altitudes where the air is thinner.  This in turn reduces drag.

Finally, at supersonic speeds, there is compressibility drag, but again, the compression wave can be used for lift.  This permits supersonic transports to cruise at much higher altitudes than subsonic transports, which again reduces drag relative to flying "in the soup".

You say all of that, and yet I don't think that this actually cancels out the inherent drag from moving through even a thin atmosphere at LUDICROUS speed.  There's a reason that all of the actual supersonic aircraft built optimize their airframes to minimize drag, and take advantage of vortex lift at slow speeds when taking off and landing.

I'm still not seeing the fundamental breakthrough that allows this to be done in a cost-efficient manner.

Quote:I'd expect the same gradual improvement for supersonic jets once they become common.

(01-24-2017, 05:57 AM)Mikebert Wrote: Looks like Trump has drawn his first red line.  Didn't take him long.

http://www.theamericanconservative.com/larison/the-u-s-shouldnt-go-looking-for-a-fight-with-china/

Trump seems to be a big hurry, he's already working on objective six. I also notice the administration is making more noise on trade than on immigration. My belief has been that his trade policies are something *he* wants, whereas his immigration policy is more of something his voters want.
Not sure where he is going with this.  Maybe its no where.

(01-24-2017, 08:34 AM)SomeGuy Wrote: I think the thing with China was largely baked into the cards.  Have been saying so for years.  Better China than China AND Russia, I suppose. 

We'll see if they double down on this, or just use it as a negotiating bit.  Let's give him the proverbial 100 days, and see how this plays out.  Not just with China, but trade/immigration, too.

(01-24-2017, 02:13 PM)Mikebert Wrote:

(01-24-2017, 08:34 AM)SomeGuy Wrote: I think the thing with China was largely baked into the cards.  Have been saying so for years.  Better China than China AND Russia, I suppose. 

We'll see if they double down on this, or just use it as a negotiating bit.  Let's give him the proverbial 100 days, and see how this plays out.  Not just with China, but trade/immigration, too.

I agree on the first.

I don't think anything will come of the China thing.  Trump would have to push the issue.

I am very interested in the trade thing.  It is possible Trump may loose interest and drop the ball on the stuff he ran on which is opposed by movement conservatives, but I hope not.