You, the pilot, arrive at the Base while others are finishing final fueling and system checks in the hours approaching dawn. 
You'll start with the X-15 already hanging from a pylon on the B-52 carrier aircraft. Don't bother with a nitty gritty total hardware preflight; the taxpayers thoughtfully provided a whole staff to do it for you. Anyway, you're cooped up in a pressure suit, prebreathing 100% oxygen.


After entering the cockpit, strap in and and run through the interior check. That's 120 checklist items, ending with "close canopy". By now the B-52 is supplying power, breathing oxygen, nitrogen, and liquid oxygen to top off loss from the oxidizer tank.

That LOX loss is due in part to precooling the engine, which you initiate in the captive takeoff checklist. While precooling, LOX flows through almost all of its usual path to the engine, then dumps overboard at the liquid oxygen prime valve. You'll precool for 10 minutes, then start a schedule of 20 minutes off and 7 1/2 minutes on.

Takeoff isn't just you and the B-52.  Typical missions will add three chase planes, rescue helicopters, a C-130, and an array of ground vehicles deploying to places between your planned takeoff location and Edwards.  Some of this force goes to dry lakes that might be needed for emergency landings along the planned route of your flight.

A few things will need heat during the climb, so be sure to turn on the heaters for the windshield, your face mask, and the nose ballistic rockets (the X-15's nose, not yours). Also ask the B-52 crew about the hook heater.

Once at altitude, go through the 27-item prelaunch checklist. Among other things, you'll switch to the X-15's breathing oxygen, shut off liquid nitrogen but not gaseous nitrogen from the B-52, and start the APU's.

Next comes the 29-item precountdown checklist. Among other things, you will:

• Stop LOX transfer from the B-52.


• Cycle the propellants tanks from vent to jettison, then to pressurize.


• Check the flight controls and trim settings. Launch control surface deflections should be 0 degrees for everything except the horizontal stabilizers, which should be 0 to 2 degrees leading edge down. Be careful - if the position's too far off when you drop, the X-15 can pivot on its pylon and slide into the engines just outboard on the B-52.


• Turn on instrumentation.


• Start the final engine precool cycle.


• Set the engine prime switch to PRIME. This opens the liquid oxygen and ammonia main feed valves and the hydrogen peroxide upstream safety valve for the turbopump, and it feeds helium to the engine control and purge systems. It takes 30 seconds to complete priming.


• Depress the turbopump idle button. This opens its H2O2 downstream safety valve, allowing the pump to begin running. When it's brought ammonia pressure up to 210 psi, the turbopump speed control system will take over to keep it at idle speed.


• Set the igniter idle switch to IGNITER. Now you have 30 seconds to finish preparations, drop, and fire the XLR-99's main chamber or to shut down. Don't leave the igniter on longer, or the XLR-99 will be damaged by overheating.

• The engine is purged with helium for 2 seconds.


• Three spark plugs are energized in the first stage igniter, which is a small combustion chamber ahead of the 2nd stage igniter and main chamber.
  
  
• Ammonia and gaseous oxygen enter the 1st stage igniter and start burning. The gaseous oxygen is produced by routing liquid oxygen through a heat exchanger that surrounds the turbopump exhaust.
  
  
• When chamber pressure rises sufficiently, gaseous nitrogen from the B-52 flows in to mix with the 1st stage igniter gases.
  
  
• Ammonia and LOX begin flowing to the second stage igniter, which is a larger chamber, where they're ignited by the jet of burning gas from the 1st stage. This igniter alone produces 1,500 pounds of thrust.

They're serious about that 30 second time limit for either lighting up or shutting down. When there's 7 seconds more of idle time allowed, an IDLE END caution light comes on. When time runs out, a NO DROP light tells you to shut it down.

So... when you get through the brief countdown and you drop, don't waste much time before moving the throttle from OFF to at least 50%. That'll light the main chamber, giving you the second part of a big one-two punch.

Part 1 was the drop itself. Starting to fall may sound like a gentle and mellow start, but it can feel more like being catapulted straight down. In the early flights even a short countdown wasn't adequate preparation when the B-52 crew initiated the drop -- NASA soon rerigged the system so that it would be the X-15 pilot who tripped the release, giving you at least a feeling of being just a bit more ready for the event.

This pilot report is split into these four parts:

    1.  X-15 General Description & Walkaround
    2.  X-15 Cockpit Check
    3.  X-15 Flight:  Heading Out to Launch
    4.  X-15 Flight:  Flying the Mission and Returning

Related to all four sections:

    Photo credits and pointers to related resources
..