Ram jet engines

[Rupert_Baehr]

To be fair, the solution to the problem with the ramjet was to add variable geometry shock bodies in the inlet, compressor stages (on 2 or 3 concentric shafts), annular (or cannular) combustion chambers, multiple turbine stages and bypass ducts. - The original ramjet is still there (it's in the afterburner now) but unless you're in a real hurry (and are prepared to accept the high fuel consumption) you don't use it very often.

[HeadingNorth]

I think we've moved beyond my technological event horizon now, but I'll just smile and nod and pretend I understand you.

[Stormy]

I did my propulsion courses about 40 years ago. At the time (perhaps suspecting that somebody would try to make one ) the lecturer said: "Too dangerous! - Don't even think about it! You can't make a safe ramjet."

 

The engine in the SR71 had (I was told) very sophisticated variable-geometry shock bodies in the inlet and because it was a turbojet which operated as a ramjet only at high speed and high altitude it was fairly 'conventional' below cruise altitude. - Although it had a 'starter' chemical (used to get the fuel burning) which was pretty dangerous.

 

Oxygen-fuelled scramjets sound like fun, but since the aircraft would have to be taken to altitude on a 'piggyback' carrier, it'll probably be some time before they are commercially feasible.

 

It probably wouldn't matter, anyway. No matter how fast you could get the thing to go, flying would still be a long, drawn-out business. The check-in period would probably increase by rather more than the flight time decreased.

 

And they'd still manage to lose your baggage.

 

'If you've time to spare - go by air.'

 

And the SR-71, although beautiful and technologically brilliant wasn't exactly the safest form of travel! I believe about a third crashed? The technology would have to come a long long way before it could be viable for commercial operations. Having said that, I'd pay to have a go in one! Although, about 40 years later you would think that the technology has come a long way since then anyway. I guess the focus has shifted from ultra-fast propulsion to better satellite and UAV technology.

[Rupert_Baehr]

I wouldn't go so far as to say 'air travel has had its day' because quite clearly, there are still very many hundreds of thousands of people who travel by air or both business and pleasure every day.

 

BUT:

 

Up until about 5 years ago, if a company or an organisation (particularly one with branches in geographically diverse locations) wanted to hold a conference, people got on aircraft, flew to a common destination, held the meeting then flew back home again. The travel time was seen as being unavoidable and it ws often argued "You can't beat talking to people in person."

 

Nowadays, however, high-speed internet connections are widely available, video conferencing has improved dramatically and many companies are feeling the financial pinch. Even those that aren't often question the advisability of having highly-paid executives wasting time trotting around the globe.

 

Airlines make most of their money from business travellers, but there are fewer business travellers.

 

The advent of huge cattle trucks (such as the Airbus A380F) will mean that more passengers can be carried at any one time, but the choice of departure times will be reduced, the time to process the large numbers of passengers (both before and after flight) will increase and I very much doubt that the extra capacity will be used to give the passengers more leg room.

 

If there are fewer business passengers, tourist passengers will end up paying more.

 

It may be that there won't be much overall change in total passenger capacity, but the number of flights on many routes may decrease, the price will increase and the standard of service will decrease (the airlines will try to save money wherever they can.)

 

The standard of service provided by many airlines has already fallen. Security checks are a necessary part of life - unfortunately - but additional charges for luggage, reductions in the number of cases you can take on long-haul flights, surly staff who couldn't care less about the passengers and airlines which seem to think they are doing you a favour are unlikely (IMO) to encourage people to fly with them more often

 

I doubt that the western world is going to see a sudden surge in demand for flights or in the number of airlines anytime soon.

 

Perhaps tourism will alter?

 

My wife retires next summer. We will probably be doing one return transatlantic trip each year. But (if I have my way) it will be on a ship. - Not a cruise liner, a freighter which carries passengers. We won't be 'time restricted' so a 7-10 day each way crossing won't be a problem.

 

If the UK ever managed to integrate its railway system with that of Europe (and bring its prices for long-haul rail travel down to a reasonable level) then perhaps more people will go on holiday using surface transport.

 

The last 2 years saw an increase in people taking holidays at home. Perhaps that will continue?

 

Either way, I suspect that any innovations made in air travel over the next many years will be limited to those which reduce operating costs per passenger mile.

[JFKvsNixon]

And the SR-71, although beautiful and technologically brilliant wasn't exactly the safest form of travel! I believe about a third crashed?

 

I think that it was a bit more than that - 12 out of 31 were lost, but only one person died as a result of those losses.

[esme]

I think we've moved beyond my technological event horizon now, but I'll just smile and nod and pretend I understand you.

 

as I understand it, which is probably wrong, a ramjet is basically like a jet engine but without the turbine

 

so, [waffle mode on] this is how I see it, and I have no problem with someone telling me it's rubbish, just tell me how it does work if I'm wrong as I'm very interested to know

 

a jet has a turbine to suck air in, compress it, then fuel is added and ignited and it leaves out the back with a higher speed than it came in thus producing thrust

 

which is your basic suck, squeeze, bang, blow process common to a lot of engines, this just happens in a straight line

 

a ramjet relies on it's forward speed to get the air into the engine and compress it before combustion, so it's got to be moving pretty fast before it starts to work

 

the basic problem is how to keep the air in the engine long enough to mix in the fuel and ignite it in a controlled explosion

 

if the air travels too quickly it will blow the flame out of the back of the engine and the engine won't work

 

one solution is to make the engine longer to keep the burning fuel in there but this adds to weight and increases drag and you hit a diminishing return

 

at mach 1, if the process takes 0.01 of a second then the air travels 330x.01 metres through the engine so the engine needs to be at least 3.3 metres long to contain the reaction, I just pulled the 0.01 out of the air the real figure is probably a lot smaller but it illustrates the point

 

a better solution is to slow the air down when it's in the engine by making it turbulent, this is done by putting something in the way of the smooth air flow, these are called "shock bodies"

 

however a fixed shock body produces a different pattern of turbulence at different air speeds and if you change the shape of the shock body you can optimise the airflow through the engine to burn less fuel for the same thrust, hence variable geometry shock body

 

[disengage waffle mode]

 

the guys who dream this stuff up are geniuses as far as I'm concerned

 

*sits back and awaits the correction*

[Alcoblog]

All very simple stuff ... Ion drive is the way to go! (as proven by my recent success of the Fray Bentos UFO ...Can't say too much though, legal reasons!)

[Stormy]

I wouldn't go so far as to say 'air travel has had its day' because quite clearly, there are still very many hundreds of thousands of people who travel by air or both business and pleasure every day.

 

BUT:

 

Up until about 5 years ago, if a company or an organisation (particularly one with branches in geographically diverse locations) wanted to hold a conference, people got on aircraft, flew to a common destination, held the meeting then flew back home again. The travel time was seen as being unavoidable and it ws often argued "You can't beat talking to people in person."

 

Nowadays, however, high-speed internet connections are widely available, video conferencing has improved dramatically and many companies are feeling the financial pinch. Even those that aren't often question the advisability of having highly-paid executives wasting time trotting around the globe.

 

Airlines make most of their money from business travellers, but there are fewer business travellers.

 

The advent of huge cattle trucks (such as the Airbus A380F) will mean that more passengers can be carried at any one time, but the choice of departure times will be reduced, the time to process the large numbers of passengers (both before and after flight) will increase and I very much doubt that the extra capacity will be used to give the passengers more leg room.

 

If there are fewer business passengers, tourist passengers will end up paying more.

 

It may be that there won't be much overall change in total passenger capacity, but the number of flights on many routes may decrease, the price will increase and the standard of service will decrease (the airlines will try to save money wherever they can.)

 

The standard of service provided by many airlines has already fallen. Security checks are a necessary part of life - unfortunately - but additional charges for luggage, reductions in the number of cases you can take on long-haul flights, surly staff who couldn't care less about the passengers and airlines which seem to think they are doing you a favour are unlikely (IMO) to encourage people to fly with them more often

 

I doubt that the western world is going to see a sudden surge in demand for flights or in the number of airlines anytime soon.

 

Perhaps tourism will alter?

 

My wife retires next summer. We will probably be doing one return transatlantic trip each year. But (if I have my way) it will be on a ship. - Not a cruise liner, a freighter which carries passengers. We won't be 'time restricted' so a 7-10 day each way crossing won't be a problem.

 

If the UK ever managed to integrate its railway system with that of Europe (and bring its prices for long-haul rail travel down to a reasonable level) then perhaps more people will go on holiday using surface transport.

 

The last 2 years saw an increase in people taking holidays at home. Perhaps that will continue?

 

Either way, I suspect that any innovations made in air travel over the next many years will be limited to those which reduce operating costs per passenger mile.

 

 

Your conclusion about innovations being limited to reducing passenger cost per mile is of course correct, but to me it is such a pity that this is the case. In the 50s and 60s the technology leapt forward, and we seemed to be getting faster and faster. If we had continued with the space race in such a fashion then no doubt we would have replacements for Concorde and the Tu144. The age of the satellite and UAV somewhat negated the need for excessive speed. But like you said, it is all about cost now.

Another factor in technology advances with regardes to commercial air travel is also environmental. A lot has been made of the environmental credentials of the Boeing Dreamliner and presumably any future designs from any manufacturer will be more environmentally friendly. I am not aware whether airlines are subject to Carbon Trading laws or not? If so then this will be even more so as airlines rush to drive down costs.

 

As for Rail, partial integration of our rail network to Europe is coming. On October 19th DB (German state railways) will operate one of their trains into St Pancras as part of a publicity event/feasability study. If the safety limitations in the tunnel can be relaxed, and there are no reasons why they cant be as longer tunnels through the Alps do not have such restrictions, then we can expect a full service to Germany and possibly Amsterdam from London in the next few years. Sadly HS2 will take many many years to build as the HS1 debacle has proven, so full and proper integration from cities other than London (which is the key to unlocking the market) is still many years away.

Spain is another country which is developing its high speed network. Maybe one day we will see direct trains to Madrid and Barcelona...

[Rupert_Baehr]

...As for Rail, partial integration of our rail network to Europe is coming. On October 19th DB (German state railways) will operate one of their trains into St Pancras as part of a publicity event/feasability study. If the safety limitations in the tunnel can be relaxed, and there are no reasons why they cant be as longer tunnels through the Alps do not have such restrictions, then we can expect a full service to Germany and possibly Amsterdam from London in the next few years. Sadly HS2 will take many many years to build as the HS1 debacle has proven, so full and proper integration from cities other than London (which is the key to unlocking the market) is still many years away.

Spain is another country which is developing its high speed network. Maybe one day we will see direct trains to Madrid and Barcelona...

 

I can buy a one-day pass valid for up to 5 people to travel on buses and trains anywhere in Bavaria for €28 (provided I buy it online, or from a ticket machine. - If I buy it from a ticket office it costs €30.

 

That's hardly shabby. - I live in the South-Western part of the state, so if I wanted to go with 4 other people to, say, Bayreuth (about 250 miles each way) it would cost each of us about £4 return.

 

There are cheap ticket deals for other Länder (I would need another ticket to travel in Baden-Württemberg), cheap combination tickets, cheap country tickets, cheap country combination tickets. - Until you start considering the UK and then the prices get silly.

 

I'm well aware that crossing the channel - either on it or under it - is an additional problem, but I don't see any reason why the prices should go through the roof - other, of course, than that the UK seems determined to keep the 'Treasure Island' reputation it has earned.

 

When I lived in Norfolk, there were special offers (from time to time) for trips to Amsterdam for £40 return. They departed from a station in Norfolk, went to Harwich (where the passengers got on a high-speed ferry to Hoek van Holland) and at the other end, the passengers got on a train to Amsterdam.

 

Ryanair, Easyjet and a number of other airlines manage to make a profit offering low-cost fares - but on aircraft with very high load factors.

 

AFAIK, DB and other train companies which offer cut-price fares in Europe don't operate at a loss. - And the trains don't run nearly empty, either.

 

Commuter trains in the UK seem usually to be pretty full, but what's the load factor on off-peak services?

 

For business travellers, time is of the essence and a high-speed link is vital, but perhaps tourists (many of whom might want to break their journey at various points) would be tempted by reasonable train fares? For many of them, a train journey to a port, followed by an overnight crossing and another day on a train would be seen as a being a part of the holiday.

 

(Comparatively) long-distance train travel is popular with tourists in Europe, but at the moment, British rail companies seem not to be interested.

 

(This is a topical point for me. - Some friends of mine are coming to Europe in a few weeks time. They expressed an interest in buying tourist train tickets valid for multiple countries, but when they found out how much a ticket which included the UK cost, they decided to pass on that bit.)

[Stormy]

Prices associated with travel into/out of the UK via the tunnel are expensive due to the rule that one train must be formed of two complete sets which can be uncoupled and driven in opposite directions as required, plus the requirement that each half must be adjacant to an enterance to the middle service tunnel which means the trains are longer than a normal train. Hopefully after DB successfully operate their train into St Pancras in a couple of weeks they will also successfully lobby for the rules to be relaxed more into line with European guidelines. This should open the market and eventually drive prices down with the associated competition. As for domestic fares, they are silly and the walk on prices are far too high, especially for longer distance services. There are some good bargains to be had in advance though.