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46 votes

How did the X-15 control attitude above the Kármán line?

The X-15 had a reaction control system for all three axes using thrusters with hydrogen-peroxide monopropellant. There was an automatic as well as a manual mode. The manual mode used a single three-...
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39 votes

How did the X-15 control attitude above the Kármán line?

The X-15 has a reaction control system. In this image, it's item 2, 13 and 28, labeled 'ballistic control system'. It was operated via a joystick. Detail of two of the thrusters:
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38 votes
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Reasons why liquid anhydrous ammonia fuel chosen for the X-15? Has it been used in other rocket engines?

According to Clark's "Ignition!", German rocket scientists in WW2 had done the math on ammonia, and JPL had burned it with RFNA and WFNA oxidizers in 1949-1951. Regarding the XLR99, Clark says: ...
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32 votes

Why did the X-15 not achieve orbit?

You're confusing units. The maximum speed of the X-15 was 7274 km/h, or about 2 km/s. Orbital speed is around 8 km/s. The X-15 didn't carry enough fuel to reach orbital speed.
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13 votes

Reasons why liquid anhydrous ammonia fuel chosen for the X-15? Has it been used in other rocket engines?

The book Aerofax Datagraph 2 / North American X-15/X-15A-2 by Ben Guenther, Jay Miller, and Terry Panopalis has some more info on the history of the propellant choice (page 27): Eventually it was ...
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9 votes

Was the X-15 program a dead end for orbital insertion?

Was the X-15 capable of reaching orbit? Not on its own (it only carried enough fuel to reach 4500 mph), but with extra fuel tanks or a booster rocket, it could. Was the X-15 capable of returning ...
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8 votes
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What was the point of the Redstone rocket when there was the X-15 rocketplane?

The goal of Project Mercury as stated in 1958 was to put a man into orbit safely. In order to do that, NASA wanted to send animals, first. The Russians had done exactly that, and NASA preferred using ...
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8 votes

Reasons why liquid anhydrous ammonia fuel chosen for the X-15? Has it been used in other rocket engines?

Chiming in as a long-time member of the NH3 Fuel Association. First, a small correction. "Cryogenic" refers to gases that liquefy below -150 degrees C. As you state, ammonia liquefies at -33 degrees ....
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7 votes
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Was the X-15 program a dead end for orbital insertion?

Mach 6 buys you roughly 1.8 km/s at those altitudes. OK, let's say that X-15 reached 2 km/s for good measure. But at that speed, Newton still works against you and you're not going to perpetually miss ...
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6 votes

Reasons why liquid anhydrous ammonia fuel chosen for the X-15? Has it been used in other rocket engines?

PS to previous comment about refrigeration in the X-15. It had none, keeping weight absolutely minimal precluded it. Temperature was far more of an issue for the LOX than for the NH3. During captive ...
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4 votes

Why did the X-15 not achieve orbit?

The X-15 didn't have the capability to get to orbit, and it was never intended to. the X-15's purpose was not space flight but to test aerodynamic heating at high altitude and high speed. It's skin ...
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4 votes

Was the X-15 program a dead end for orbital insertion?

As @TildalWave notes, the X-15 had nothing close to orbital capability, and wasn't intended to. There was some early consideration of putting an X-15 on top of a SM-64 Navaho missile, but NASA went ...
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3 votes

Why did the X-15 not achieve orbit?

The X-15 was undoubtedly fast enough to reach altitudes at which the pilot could have looked into the blackness of the heavens, but high altitudes are not enough for achieving an orbital trajectory. ...
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3 votes

Reasons why liquid anhydrous ammonia fuel chosen for the X-15? Has it been used in other rocket engines?

As mentioned in one of the previous answers and according to this source the directive to use anhydrous ammonia came from Dr. Paul F. Winternitz, a propellant scientist from Austria and chief of R&...
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3 votes

Could the $C_L$ of the X-15 be calculated from the flight data near the Kármán line altitude?

The X-15 never flew at any reasonable speed close to the Karman line. The maximum speed was reached at a much lower height (around 50 km or lower) and then followed a purely ballistic trajectory for ...
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2 votes

Could the $C_L$ of the X-15 be calculated from the flight data near the Kármán line altitude?

Not sure what you're looking for — above the atmosphere the lift coefficient is going to be zero in practical terms. NASA has a free ebook ("X-15 Research Results") which might get you pointed ...
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1 vote

Was the X-15 program a dead end for orbital insertion?

There was a program called the X15B that would launch using a Titan Booster to make one orbit in 1959. From Wikipedia's North American X-15; Operational history: Before 1958, United States Air ...
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