This comes from place of ignorance, so please be kind: why "speed record" is considered Mach 6.2 when ISS ground speed is like Mach 22? There are humans there, they got up to speed and regularly come back. How it is different than going to similar velocities in thin atmospheres over 50km?
> [after hearing he has to take the top off of the Mars Ascent Vehicle] I know what they're doing. I know exactly what they're doing. They just keep repeating "go faster than any man in the history of space travel", like that's a good thing. Like it'll distract me from how insane their plan is. Yeah, I get to go faster than any man in the history of space travel, because you're launching me in a convertible. Actually it's worse than that, because I won't even be able to control the thing. And by the way, physicists, when describing things like acceleration do not use the word "fast". So they're only doing that in the hopes that I won't raise any objections to this lunacy, because I like the way "fastest man in the history of space travel" sounds. I do like the way it sounds... I mean, I like it a lot.
To be fair, calling X-15 “piloted, powered aircraft” is a stretch. While it’s piloted and powered, it’s definitely not conventional plane, i.e. aircraft. It’s a rocket that is launched from the carrier plane and has ability to land as (unpowered) glider after (unpowered) ballistic flight. In this sense it’s not different from the space shuttle: launched from the carrier vehicle, uses it’s rocket engine to go up, has orbital flight with ballistic descent, lands as a glider.
Fair record category would be “takes off under own power, sets record, lands by itself with all the equipment”. X-15 definitely doesn’t qualify.
"Aircraft" doesn't make assumptions about the power source. Piston engine, turboprob, turbojet and turbofan aircraft are all called aircraft despite all having different sorts of propulsion. All of those still breath air of course, but we don't hesitate to apply the term to experimental/prototype electric aircraft either. So an aircraft needn't breath air, and therefore having a rocket engine shouldn't be a disqualifier.
"Takes off under it's own power" is a qualification you're not the first in proposing, but it's controversial because it would disqualify many famous aircraft, such as the Bell X-1 and according to some (mostly Brazilians) the Wright Flyer. There is also the matter of carrier-launched aircraft that take off when the carrier is running flat out into the wind, let alone with a catapult; it's easy to say they are not taking off entirely under their own power. You could make a similar argument for rocket-assist JATO configurations, if the plane drops the JATOs after takeoff.
This is exactly my point, records should be apples-to-apples. This particular record should go to Shuttle or similar “aircraft”. In particular Shuttle is hard to distinguish from X-15. Same thing, but more of it.
“Takes off under it’s own power and brings all equipment back” is good limitation - otherwise you can trivially design a system that drops multi-stage booster and lands tiny glider after setting a record.
I would assume that Soyuz capsules aren't considered aircraft. They don't really fly, per se, they get launched on a rocket and then fall like a rock back to earth.
You could make a stronger argument for the Space Shuttle, which re-enters at about Mach 25, IIRC, and is gliding. But it's not doing so under power.
While I suspect you're right, Soyuz capsules do use aerodynamic lift to control descent rate and steer to the landing site. In some ways they are very, very (very) inefficient gliders.
I'd expect the definition of a powered aircraft to include the ability to maintain some given flight altitude and speed for some appreciable amount of time.
It is possible to do something sort of like this in a space capsule returning to Earth, where you muck up your entry vector and come in at too shallow an angle. You can then (depending on the circumstances) bounce off the atmosphere, and gain altitude briefly. And then you probably come back in the atmosphere on too steep an angle, and die due to g-load or overheating.
Soyuz can be manually piloted, but are normally automated (Progress can not be piloted and is essentially the same thing after all). They're also not aircrafts.
I think the differentiator is "powered flight". The ISS relies on momentum and gravitational pull to sustain that speed. Similar with the Apollo 13 CM which reached something like 36,000 MPH on the return leg, giving the astronauts on board the moniker as the fastest that humans have ever travelled in a man made vessel - not considered a speed record per se because it wasn't using an internal power source to propel (to a major extent).
The X-15 still had to deal with the other aspects of atmospheric flight like weight (carrying its own fuel source), drag and heating due to friction etc.
The speed of sound is not a constant; in a gas, it increases as the absolute temperature increases, and since atmospheric temperature generally decreases with increasing altitude between sea level and 11,000 meters (36,089 ft), the speed of sound also decreases. For example, the standard atmosphere model lapses temperature to −56.5 °C (−69.7 °F) at 11,000 meters (36,089 ft) altitude, with a corresponding speed of sound (Mach 1) of 295.0 meters per second (967.8 ft/s), 86.7% of the sea level value. [0]
I think that, of the so-called inertial or ficticious forces, you are thinking of the centrifugal rather than the coriolis force [1].
On any of the ballistic / into space flights, you would experience weightlessness between the engine cutoff and the point where atmospheric forces became noticable -- this is what the space tourism companies are aiming for.
I do not know if any flights were conducted at a constant altitude, but note that the centrifugal force goes by the square of the angular velocity.
Also, Mach numbers depend on atmospheric temperature and therefore indirectly on altitude. Strictly speaking, a Mach number for the ISS is meaningless, and even if we are being lax, the figure of Mach 22 is not directly comparable to the X-15 record Mach number. The comparison must be made between speeds, which are, approximately, 17,000 mph for the ISS and 4,500 mph for the X-15 record.
If we disregard the relatively small difference in the radius (from the center of the earth), then my BOE calculation suggests that the reduction in weight is about 7%.
Note, however, that while the motor is running, its acceleration is the biggest contribution to weight (reaching up to 4g as the fuel weight goes down.) Once it is cut off, then our assumption of level (i.e. non-ballistic) flight assumes that the airplane is capable of generating lift equal to its weight, which implies sufficient atmospheric density for the small wings to generate that lift. This, in turn, seems to imply enough density to produce a non-trivial deceleration due to drag, which also contributes to weight. Therefore, I doubt that there is any phase of the flight where the centrifugal reduction of weight is the dominant effect.
> Does that mean that when you're flying an X15 you lose 6.2/22 = 28% of your bodyweight to the Coriolis force?
I think you mean centrifugal force. Unfortunately, no, you don't feel quite that much less weight, because centrifugal force goes like the square of the velocity, so the ratio is the square of 6.2/22, or about 0.08, i.e., only 8%.
There is a Coriolis force here too; it's just much smaller than the centrifugal force.
Consider a plane flying at ground level along the equator at groundspeed velocity v in the direction of the Earth's rotation. In the Earth's (rotating) reference frame there is a centrifugal acceleration based on the Earth's angular velocity and a Coriolis acceleration given by -2 W x v, where W is the Earth's angular velocity and v is the plane's velocity. This ends up pointing straight up in this configuration.
So in the plane's reference frame there is a straight-up centrifugal acceleration, given by (W + v/R)^2 * R = W^2 * R + 2W x v + v^2/R which is balanced by the aerodynamic and gravitational forces on the plane (which in this frame is non-accelerating), while in the Earth's reference frame there is a straight-up centrifugal acceleration given by W^2 * R and a straight-up Coriolis acceleration of 2W x v, and the plane is accelerating radially down at v^2/R due to gravity and lift combined.
Now to put numbers to this, the speed record for an X15 is about 2000 m/s, R is 6.4 * 10^6 m, and W is 1 revolution per 24 hours, or 1/86400 s^1. So the three force components look like this, if I am doing my numbers right:
W^2 * R is .00086 m/s^2
2W x v is 0.04 m/s^2
v^2/R is 0.63 m/s^2.
So the v^2/R "centrifugal force due to the plane's motion" term is by far the biggest contributor here.
It really depends on how you turn. Like, if you would go high enough to have close to none air pressure, and stop accelerating, you would feel about 0% of your body weight, being in free fall, same as ISS. You don't have to go orbital speed to be in free fall. You have to have that speed only not to fall while free falling :)
