North American Aviation X-15

Page created 1/10/99 by Jon S. Berndt
Last updated: Thursday, June 08, 2000 05:34:23 AM Central Daylight Time

Since the X-15 is a rocket powered aircraft that carries only enough fuel for a really solid two minute kick in the pants (and also since it has two metal skids for main landing gear), it must be air-dropped. Keeping this in mind, here is the command line I recommend using to start FlightGear with the X-15:

fgfs --fdm=jsb --aircraft=X15 --units-feet --altitude=60000 --uBody=2000 --wBody=150

To fire up the XLR99 you need to move the throttle up to at least 40%, at which time it will fire up. You will eventually burn all of your fuel. From then on you are a flying brick. Manage your energy correctly (altitude and airspeed) and you'll end up at the threshhold with the appropriate airspeed. Waste it and you'll be a lawn dart.

Weight:	15,560 lb. Empty 31,240 lb. Fueled 50,914 lb. Fueled (w/ext. fuel tanks)
Wing Span:	22.36 ft.
Wing Area:	200 sf. (includes 94.98 sf. in the fuselage section)
Wing chord:	10.27 ft. ¼-chord located at F.S. 345.4"
Airfoil section	modified NACA 66005 (5% thickness)
Root chord / tip chord	14.91 / 2.98 ft.
Taper Ratio / Aspect Ratio	0.20 / 2.50
Incidence / Dihedral / Twist	0 / 0 / 0
Flaps - Type - Area - Span - Inboard Chord - Outboard Chord - Deflection (max down) - Ratio flap chord / wing chord - Ratio flap area / wing area - Ratio flap span / wing semi-span - Trailing edge angle - Sweepback of hingeline	- Plain Flap 8.30 4.50 2.61 1.08 40 0.22 0.08 0.40 5.67 0
Horizontal Tail Airfoil section	modified NACA 66005 (5% thickness)
H. Tail Area	115.34 (includes 63.29 sf. covered by fuselage section)
H. Tail Span	18.08
H. Tail mean aerodynamic chord	7.05
H. Tail Root chord / Tip chord	10.22 / 2.11
H. Tail Taper ratio / Aspect ratio	0.21 / 2.83
H. Tail Sweep at ¼-chord	45
H. Tail Dihedral	-15 (reverse dihedral)
Ratio H. Tail area / Wing area	0.58
H. Tail Movable surface area	51.77 sf.
Deflection - Longitudinal, up - Longitudinal, down - Lateral differential (pilot authority) - Lateral differential (autopilot authority)	(left and right sides move in unison and differentially) 15 35 +/- 15 +/- 30
Fuselage - Length: - Maximum Width: - Maximum Depth: - Maximum depth (over canopy): - Side area: - Fineness ratio:	- 50.75 ft. 7.33 ft. 4.67 ft. 4.97 ft. 215.66 sf. 10.91
Engine:	Throttleable (40% - 100%) liquid propellant XLR99-RM-2 single chamber rocket engine. Chamber Pressure: 40.82 bar Isp: 276 sec. (sea level: 239 sec.) Burn time: 90 sec. Engine Mass: 915 lb. Diameter: 4.6 ft. Nozzle Diameter: 39.3" Expansion Ratio: 9.80 Thrust/Wt: 64.50 Coefficient of Thrust: 1.87 (vacuum), 1.63 (Sea Level) Fuel flow: 13,000 lbs./min. at max thrust
Fuel:	LOX (LO₂)/ Anhydrous Ammonia (NH₃) LOX Tank Capacity: 1003 gallons Ammonia Tank Capacity: 1445 gallons
Thrust:	59,000 lb. Vacuum 57,000 lb. @45,000 ft. 51,090 lb. @Sea Level
Inertias: (zero fuel)	Ixx: 3650 slug-ft² Iyy: 80,000 slug-ft² Izz: 82,000 slug-ft² Ixz: 590 slug-ft²
C.G. location:	0.22 cbar (plus or minus 1%)
	The X-15 first flew powered on September 17 1959. Fastest speed attained was Mach 6.72 (3937 knots) on 28 June 1964 (w/external fuel tanks) Highest altitude attained was 354,200 feet on August 22, 1963. Total flights made: 199

From the Pilot's Seat
by William H. Dana
From Science News, 24 February 1968

Before describing the specific sensations of flight in the X-15, let me first put these comments in context. The X-15 is the most marvelously engineered piece of hardware I have ever flown, and by listening to the remarks of my fellow pilots who have flown it, I conclude that they share my sentiments. The X-15 operates in an environment that varies from the pure vacuum of near space to the heavy air loads of 2,200 pounds per square foot near the earth. Shock waves strike on its control surfaces from the time it crosses Mach 1 on its way up to its maximum speed of seven times the speed of sound and until it decelerates to subsonic speeds again. During no two seconds of supersonic flight are these shock impingements identical. Yet the X-15 remains totally responsive to the commands of the pilot from launch to landing.

Wrong. The very nature of the airplane's design mission dictates that an X-15 flight will be a challenge to the men who work with it, and ultimately, to the man who flies it. Hundreds of hours are spent in the precise planning stage that precedes every flight. Once the complicated flight plan is completed, another 50 hours are spent practicing the 10-minute flight in an electronic simulator. The last two hours prior to launch are spent in ground checks and inflight system checks that are so routine that they mock the forthcoming events.

The launch itself provides the first surprise of the flight. The act of leaving the wing of the mother ship in free fall gives the X-l5 pilot the sensation that he was fired off the mother ship's shackles by some hidden cannon. This sensation is not eased until the rocket engine lights one to two seconds after launch.

Then begins as busy a minute-and-a-half as most pilots ever want to experience. In that short time, the X-l 5 accelerates from subsonic speed to about six times the speed of sound. A myriad of events take place in this 90 seconds: the pull-up to climb altitude; the maintaining of this climb angle to the designated pushover point; monitoring of speed, altitude, and air loads to ascertain that the planned flight is being flown; manipulation of switches to trigger the experiments onboard; and finally shutdown of the engine at the prescribed maximum velocity. All of these events are performed under an acceleration that presses the pilot into the back of his seat with two to four times the force of gravity.

A time deviation of one second in the performance of any of these events can mar the quality of the important data being acquired.

Engine shutdown brings some relief of physical stress, but the workload continues. If the flight is an altitude mission, that is, if it leaves the atmosphere, the pilot must operate attitude control rockets to keep the X-15 upright and weathervaned along the flight path until the atmosphere is reentered.

Then come the loads of reentry; the pilot is forced down into his seat with five times his normal weight as the X-15's fall is broken. If the mission is a heating research flight, the craft remains within the atmosphere, and at the speed it travels the air loads are massive, usually half to three-quarters of a ton per square foot. Any maneuvering transmits these loads to the pilot; at Mach 5, for example, a simple twenty degree change of heading requires a 5 "g" turn for ten seconds.

Whatever its mission, eventually the X-15 decelerates and maneuvers to a position over the dry lake near NASA's Flight Research Center at Edwards, Calif., and the pilot finds himself once again in an environment familiar to him. The craft is now subsonic, and the pilot has practiced the X-15 approach pattern hundreds of times in an F-104 jet. The approach is relaxed and the landing is straightforward.

The flight has ended and the pilot invariably reflects that the mission was challenging indeed. Therefore, the satisfaction of its successful completion is great, and, more than at any other time, the pilot longs for the next flight.