5,000kph and other questions....

[Garuda]

I used the MGT vehicle rules to create a jet fighter. It has a few nifty extras like a sealed environment so it can reach orbit and an ejector cocoon as you wouldn't want to bail out in orbit without one. It has heat shielding so that it doesn't burn up on re-entry.

After all the extras I still had some M3 left so I turned it all over to the power plant (jet). The extra power meant my plane's top speed was almost 5,000kph - which is allowable under the max speed and is akin to one of the examples in the book - the spy plane.

Here's my question: What effects does travelling at 5,000kph have on the pilot's body and his reactions?

Taking speeds even further when does the pilot start suffering from 2G, 3G etc and does the local gravity of the world have a significant impact on this?

I was also just wondering when I'd need to 'invent' artificial gravity cockpits and what TL such a cockpit might be?

 

[rust]

Here's my question: What effects does travelling at 5,000kph have on the pilot's body and his reactions?

The speed itself does not have any effect at all, only acceleration and de-
celeration do. So, if the pilot takes his time to reach the speed by accele-
rating only with a low G-value, there are no effects.
As for acceleration, under normal circumstances 6 G is about the upper li-
mit, and even that is enough to cause some pilots to become unconscious.

Taking speeds even further when does the pilot start suffering from 2G, 3G etc and does the local gravity of the world have a significant impact on this?

The pilot only suffers from G-values when his plane accelerates or decele-
rates, not because of the speed itself.
As long as his plane has enough thrust to overcome the gravity of the pla-
net, its effects are negligible - unless the plane reaches escape velocity,
in which case it may leave the planet's gravity field and move out into space.

 

[phavoc]

Here's my question: What effects does travelling at 5,000kph have on the pilot's body and his reactions?

Taking speeds even further when does the pilot start suffering from 2G, 3G etc and does the local gravity of the world have a significant impact on this?

I was also just wondering when I'd need to 'invent' artificial gravity cockpits and what TL such a cockpit might be?

As was pointed out, speed itself is relative, and therefore not an issue. To answer your question about reactions, when travelling at very high speeds, you cannot do quick maneuvers, as the stress would rip apart your aircraft. A fighter in a dogfight at Mach1 can do all kinds of maneuvers, yet you travelling at 5000Kph means that in order for you to turn around you need to make a very wide, well-thought out turn to avoid stressing your aircraft structure.

Trained pilots can operate at higher g-thresholds than people. Typically they can handle a 6G maneuver without blacking out, but any more than that then there is a risk of unconsciousness. They also wear special G-suits that enable them to take higher G than someone who is not wearing it.

Anti-gravity is available at TL9, so you could in fact put in a inertial compensator, however your aircraft frame is still going to be limited to its designs. From what I have read, with today's aircraft technology, you could build an unmanned fighter that can take around 12g's of stress during a dogfight and keep on going. But a human pilot can't take that. That 12G is about the upper limit of what we can design today.

One word of wisdom about arming your fighter - guns won't work. The US built the YF12-A interceptor (later modified into the SR-71) and put guns on it to shoot down Soviet bombers. Unfortunately the aircraft tended to exceed the muzzle velocity of the guns, which the designers didn't take into effect. The bullets fell out of the gun... So they yanked the guns and installed a missile bay. If you arm yours, use lasers or missiles. Don't make the same mistake the guys at the Skunk Works did!!!

 

[Gaidheal]

"One word of wisdom about arming your fighter - guns won't work. The US built the YF12-A interceptor (later modified into the SR-71) and put guns on it to shoot down Soviet bombers. Unfortunately the aircraft tended to exceed the muzzle velocity of the guns, which the designers didn't take into effect. The bullets fell out of the gun..."

Errr, no. The gun and ammunition are travelling at the same speed as whatever they are attached to, which is to say that the muzzle is already doing 5 Mm/h (in the example given) and the bullet achieves a velocity with a large magnitude relative to that, directly away from it; I.E. 5 Mm/h + "muzzle velocity" listed in the manual. Methinks you need to study your physics again ;¬)

 

[rust]

The real problem with very fast aircraft and guns is that the projectiles
fired by the gun tend to lose speed, and so the aircraft can catch up with
them under certain conditions, for example when firing upwards and then
diving into the trajectory of the falling projectiles - an unfortunate pilot
with a bad sense of space and time could manage to shoot down himself
instead of the enemy.

However, this is very hypothetical, I have never heard of a case where
a jet fighter pilot really managed to endanger himself in this way.

 

[dreamingbadger]

http://en.wikipedia.org/wiki/F-11_Tiger

apparently the first aircraft to shoot itself down...

 

[Galadrion]

The other problem with projectile weaponry - and far more pertinent to a fighting vehicle - is that accuracy is going to suffer greatly for any sort of unguided ordinance. Effective range for such munitions can shorten by up to 30%, and when you add to that the consideration that the pilot will be crossing that range at a higher speed as well, his time to take the shot tends to shorten at an exponential rate.

Missiles, as they are guided munitions (whether self-guided or by telemetry), don't have the same problems with shortened range. Thus, they are to be preferred in situations where effective energy weapons are not available.

 

[rust]

apparently the first aircraft to shoot itself down...

:shock:

Thank you for the link, I did not think that this really could happen.

 

[dreamingbadger]

Fact is often stranger than fiction etc...

 

[BP]

The first words from the pilot are reported to have been:

• See, I told you so!

(Just kidd'n I made that up - please don't add it to wikipedia...)


reference: Murphy's Law (#1) - 'Anything that can go wrong will go wrong'

 

[Gaidheal]

"apparently the first aircraft to shoot itself down..."

Haha! Classic stuff. I didn't know that either, although I did know it was theoretically possible, I would have said that the major reason is the engagement window - you need some essentialy super-human reactions and top-notch thinking to attempt 'going to guns' at the kind of speeds mentioned in the first post but even at real world fighter speeds you quickly reach a situation where you want to want to engage at BVR (with a sophisticated and very fast missile) or not at all, as anything else is unfeasible.

 

[dreamingbadger]

"apparently the first aircraft to shoot itself down..."

Haha! Classic stuff. I didn't know that either, although I did know it was theoretically possible, I would have said that the major reason is the engagement window - you need some essentialy super-human reactions and top-notch thinking to attempt 'going to guns' at the kind of speeds mentioned in the first post but even at real world fighter speeds you quickly reach a situation where you want to want to engage at BVR (with a sophisticated and very fast missile) or not at all, as anything else is unfeasible.

so a lot WVR engagements in the modern world take place at mid range rather than maximum speed, the corner on a F!6 for example is something of the order of 400 ish knots... but this is a sustainable speed, howthis changes in a CG world .. i'm not quite sure... but it turns out turning slows you down...

 

[mrfingle]

Guns on a fighter are for ground attack in the 21st Century and no other reason. The issue with 'dog-fighting' missiles is that while they initially travel fast, their speed only lasts as long as the rocket motors are burning and then drops off dramatically due to wind resistance as soon as the weapon is 'coasting'. Add to that a few positioning turns for the missile to get to where it wants to be for maximum lethality and all its speed is lost and it dropping out the sky before you know it.

From the target's perspective, you therefore need to be able to turn very fast as the missile gets close so that you can force ti to bleed airspeed. To do this you need to remove whatever it is that is the limiting factor of the g-rating of the aircraft namely the seat-stick interface (aka the pilot). So you get faster UAV/drone/UCAV aircraft which can out-turn missiles so you get faster missiles and so on.

Best bet is to go for something that hits them before they realise they are being targetted - which in traveller terms is railguns or lasers

But going back to the initial question regarding g-loading, as has been expressed in this thread, speed has no impact on 'g' apart from the fact that you need to be going fast to pull lots of 'g' or you'll fall out the sky. 3g is the amount of accelleration I would need to subject my body to so that it would weight 3 times what it does when I'm standing on the earth's surface.

This gets interesting (well it does to me) when we take it to extra-terrestrial (i.e. traveller) environments as what reference do we use? I can fly around in Jupiter's atmosphere and pull 3g relative to my weight on Jupiter. I can fly in Mars' atmo and pull 3g relative to Mars. But my jupiter 3g is 6.3 times more than my mars 3g and 2.5 times more than my Earth 3g. Told you it was interesting

 

[Silvereye]

A few things you may want to consider with a futuristic jet, especially if it's orbital capable.

Jet turbines will need an oxidant to function. They will not function at extreme altitudes, (very low air pressures) and especially out of an atmosphere unless you take your oxidant with you.

At TL 7 Lasers become available. A starship class laser turret will probably be easily installed as a powered anti-aircraft mount weighing a few tons, and will probably be considered to have line of sight range in atmosphere. A decent (military spec) sensory system will have any aircraft shot down almost as soon as it's detected.

To beat the laser, you'll need to avoid being spotted, so either go for speed, stealth features and countermeasures and decoys (and reflec armour). The drone fighter/bomber - remotely controlled is certainly an interesting consideration, as this could be a method of shrinking the aircraft size (do away with life support systems) and doing away with that squishy pilot that is limiting the airframe.

Or you hide in the terrain so the aircraft is out of line of sight. So slow (for an aircraft), high manouvreability, heavier armour, and lots of payload (higher-tech Apache gunship) maybe add stealth and decent countermeasures as standard anyway. This vehicle would probably benefit from a human crew as in field decision making is pretty vital.

 

[Rikki Tikki Traveller]

The USAF is about to test their X-51 Hypersonic test aircraft. It will be capable of reaching over 6,000 kph (Mach 5) using a Scramjet engine and jet fuel. They have previously tested the X-43A which reached Mach 10 using a scramjet design.

So hypersonic flight is definitely doable with a reasonably sized vehicle. The old SR-71 was ALMOST hypersonic.

I figure hypersonic piloted flight is a TL-8 technology, which we are making experimental versions of right now.

By late TL-8 or early TL-9, you should have hypersonic passenger transports. Once gravitics come in at TL-9, then hypersonic travel should be very common since you no longer have to waste all that space on wings and lifting devices.

Also, some time around TL-8 a Multi-Mode engine should be developed with will reconfigure itself from a turbofan at subsonic speeds, a ramjet at supersonic speeds, a scramjet at hypersonic speeds and then into a rocket when it reaches space. This Single-Stage-To-Orbit (SSTO) engine will significantly reduce the fuel needed to reach low orbit and should allow a TL-8 or TL-9 society to have a significant presence in planetary orbit before the invention of gravitics.

 

[AndrewW]

The USAF is about to test their X-51 Hypersonic test aircraft. It will be capable of reaching over 6,000 kph (Mach 5) using a Scramjet engine and jet fuel. They have previously tested the X-43A which reached Mach 10 using a scramjet design.

Well, the X-43A almost achieved Mach 10, was just under that on its last flight.

By late TL-8 or early TL-9, you should have hypersonic passenger transports. Once gravitics come in at TL-9, then hypersonic travel should be very common since you no longer have to waste all that space on wings and lifting devices.

There are designs out there that use wing space for passengers, dunno if any will ever be developed though.

 

[Rikki Tikki Traveller]

Designed yes, actually built or tested, no. Heck, I had some friends in Grad School that designed a hypersonic passenger jet back in the early 90s using "off the shelf" technology.

Right now it is more about cost than ability. The USAF spent about $250 million on the X-51, which is a piddlingly small amount of money. If we wanted to do it, we could, but there isn't money (interest) right now.

 

[AndrewW]

Designed yes, actually built or tested, no. Heck, I had some friends in Grad School that designed a hypersonic passenger jet back in the early 90s using "off the shelf" technology.

Right now it is more about cost than ability. The USAF spent about $250 million on the X-51, which is a piddlingly small amount of money. If we wanted to do it, we could, but there isn't money (interest) right now.

Yup. It's having the will to do it.

 

[rust]

Yup. It's having the will to do it.

Russia and China are obviously willing to do it:

http://en.wikipedia.org/wiki/Leninetz_Ayaks

 

[Rikki Tikki Traveller]

Putting this back into Traveller perspective, I would say that Hypersonic transports are TL8. What we are building now in the real world are prototypes and experimental designs.