Air performance

[Phoenix_Dragon]

Originally Posted by Varyon

I'm pretty certain most modern fighter craft don't have a full 1G of acceleration, so they should absolutely be built with smaller systems.

Most modern fighters are right around 1.0 thrust-to-weight ratio, which would be 1G acceleration. The F/A-18 is listed at 0.96 T:W when fully loaded, pushing up to 1.13 by the time it's burned half its fuel. Many modern fighters are above 1.0 even when fully loaded. It's quite hard to find a modern fighter that has a low enough T:W to need smaller systems instead of just rounding to 1.0.

[RyanW]

Originally Posted by Phoenix_Dragon

Most modern fighters are right around 1.0 thrust-to-weight ratio, which would be 1G acceleration. The F/A-18 is listed at 0.96 T:W when fully loaded, pushing up to 1.13 by the time it's burned half its fuel. Many modern fighters are above 1.0 even when fully loaded. It's quite hard to find a modern fighter that has a low enough T:W to need smaller systems instead of just rounding to 1.0.

The F-15 is famously capable of essentially ballistic flight, not dependent on aerodynamic lift at all. That was used for launching the ASM-135 ASAT.

[Anaraxes]

There's more to the max speed than T/W ratio and coefficient of drag (important as those are). For instance, for quite a while, top views of the SR-71 were classified and photos were prohibited, because that view allowed people to to measure the angle from the tip of the nose to the engine inlets, and thus the speed at which the shock wave from the nose during supersonic flight would bend back into the engines, putting a cap on the speed. Move the engines inboard a little bit, and the plane would go a little faster. (Assuming there's not something else bad that happens in that case.)

Spaceships is meant to build spaceships, not aircraft. It's not surprising if pushing it's already optimistic numbers out of its scope leads to slightly wonky results. Though I don't find 2500 mph out of line for a spacecraft that for some reason is forced to operate in atmosphere -- especially when they don't have airbreathing engines and thus limitations like the above.

[ericbsmith]

Originally Posted by RyanW

The F-15 is famously capable of essentially ballistic flight

Most modern fighters are, if not under normal flight conditions then certainly under any one of: Afterburner thrusting, no payload, or partial fuel load.

But as others have said, Spaceships is extremely optimistic in a number of ways. One thing to consider is what Spaceships considers "streamlined" is actually a radical streamlining only found on a few aircraft, because that level of streamlining is necessary to survive reentry. Most realistic aircraft, including TL7 fighters, don't actually have that level of streamlining.

[Fred Brackin]

All numbers about real world aircraft performance are simplifications in one way or other. For example check out Operation Sageburner at the link below.

The Navy was setting records and putting its' thumb in the USAF's eye while they were the only ones with the brand new F-4 Phantom. One of those digital thrusts was setting a new low altitude speed record. That was just over 900 miles per hour at ana ltiude of no more than 125 ft above sea level. I've heard they went as low as 50 ft.

The usual number given for an F-4's top speed is as high as 1600 mph depending on altitude and many other factors. Check the World Records section.

https://airandspace.si.edu/collectio...m_A19690213000

....and if some of those numbers are surprisingly higher than what you find for an F/A-18 the F/A-18 wasn't designed for supersonic sprinting. It's a seldom used capability in combat aircraft and the amount of experience between the design periods for the F-4 and the F/A-18 have shown that..

Speed, engine power and other things depend heavily on many factors. That 2500 is probably a reasonable number for a hypothetical mature TL8 follow on to the TL7 SR-71 that would be using turbo-ramjets or scramjets as the first part of an orbital flight plan.

[Anthony]

Honestly, the formula for peak airspeed in spaceships is complete nonsense, but doing a better job is mostly out of scope.

[Fred Brackin]

Originally Posted by Anthony

Honestly, the formula for peak airspeed in spaceships is complete nonsense, but doing a better job is mostly out of scope.

Doing a truly accurate formula for winged aircraft with airbreathing engines is too complex for anything except a highly capable supercomputer program using far, far more data than any game system would supply..

[Anthony]

Originally Posted by Fred Brackin

Doing a truly accurate formula for winged aircraft with airbreathing engines is too complex for anything except a highly capable supercomputer program using far, far more data than any game system would supply..

Doing even a modestly accurate one is well into "don't try this without a computer" range.

[pgb]

Originally Posted by Anaraxes

Spaceships is meant to build spaceships, not aircraft. It's not surprising if pushing it's already optimistic numbers out of its scope leads to slightly wonky results. Though I don't find 2500 mph out of line for a spacecraft that for some reason is forced to operate in atmosphere -- especially when they don't have airbreathing engines and thus limitations like the above.

I appreciate it's out of primary scope, but the numbers are there. They just seem off, especially given that my "design" is so unspecialised.

Originally Posted by Fred Brackin

Doing a truly accurate formula for winged aircraft with airbreathing engines is too complex for anything except a highly capable supercomputer program using far, far more data than any game system would supply..

Of course. I'm certainly not expecting any great accuracy. But a different set of numbers in the air speed table wouldn't be any more complex. I'm just a bit surprised that a generic design available at any TL (7+) and any size performs so much better than most specialised real examples.

[Ulzgoroth]

Originally Posted by ericbsmith

But as others have said, Spaceships is extremely optimistic in a number of ways. One thing to consider is what Spaceships considers "streamlined" is actually a radical streamlining only found on a few aircraft, because that level of streamlining is necessary to survive reentry. Most realistic aircraft, including TL7 fighters, don't actually have that level of streamlining.

Reentry vehicles are not particularly streamlined as a rule. They're not trying to minimize aerodynamic drag, if anything rather the opposite. Their aerodynamic design largely focuses on stably maintaining a heat-shield-first attitude.

Where exciting streamlining comes in is mostly for very fast air-breathing craft with aerodynamic control surfaces. (A rocket stack could be considered pretty streamlined too, but it's a kind of boring streamlining since it doesn't really want to interact with the air at all.)