science

X-15 Flight 91

X-15 Flight 91 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand X-15 Flight 91 rather than just read about it. In short: X-15 Flight 91 was an August 22, 1963 American crewed sub-orbital spaceflight, and the second and final flight in the program to fly above the Kármán line, which was previously achieved during Flight 90 a month earlier by the same pilot, Joseph A. Walker.

Key takeaways

X-15 Flight 91 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect X-15 Flight 91 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of X-15 Flight 91 from memory before moving on to harder problems.

Reference excerpt

X-15 Flight 91 was an August 22, 1963 American crewed sub-orbital spaceflight, and the second and final flight in the program to fly above the Kármán line, which was previously achieved during Flight 90 a month earlier by the same pilot, Joseph A. Walker. It was the highest flight of the X-15 program. Flight 91 was the first internationally recognized spaceflight of a reused spacecraft, as Walker had also flown plane number three on the previous sub-orbital spaceflight over the Kármán line on July 19. The flight was air-launched from a modified Boeing B-52 Stratofortress support plane over Smith Ranch Dry Lake, Nevada, United States. Walker piloted the X-15 to an altitude of 107.96 km and remained weightless for approximately five minutes. The altitude was the highest crewed flight by a spaceplane to that time, and remained the record until the 1981 flight of Space Shuttle Columbia. Walker landed the X-15 about 12 minutes after it was launched, at Rogers Dry Lake, Edwards Airforce Base, in California. This was Walker's final X-15 flight.

Crew

Mission parameters Mass: 15,195 kg fueled; 6,577 kg burnout; 6,260 kg landed Maximum altitude: 107.96 km Range: 543.4 km Burn time: 85.8 seconds Mach: 5.58 Launch vehicle: NB-52A Bomber #003

Mission highlights On this flight, Joe Walker became the first person to enter space twice. He had a maximum speed of 3,794 miles per hour (6,106 km/h) and a maximum altitude of 354,200 feet (108,000 m). Second and final X-15 flight over 67 miles (108 km). Unofficial altitude record set for class. Highest altitude achieved by X-15. Last flight for Walker in X-15 program. Number 1 left RCS nozzle froze up. First flight with altitude predictor instrument (needed calibration). The mission was flown by X-15 #3, serial 56-6672 on its 22nd flight. Launched by: NB-52A #003, Pilots Russell Bement & Lewis. Takeoff: 17:09 UTC. Landing: 18:56 UTC. Chase pilots: Wood, Dana, Gordon and Rogers. The X-15 engine burned about 85 seconds. Near the end of the burn, acceleration built up to about 4 G (39 m/s²). Weightlessness lasted for 3 to 5 minutes. Re-entry heating warmed the exterior of the X-15 to 650°C in places. During pull-up after re-entry, acceleration built up to 5 G (49 m/s²) for 20 seconds. The entire flight was about 12 minutes from launch to landing.

Notes

References Goodwin, Robert (2000). X-15: the NASA mission reports, incorporating files from the USAF. Burlington, Ontario: Apogee Books. ISBN 1-896522-65-3. Jenkins, Dennis R. (June 2000). Hypersonics Before the Shuttle: A Concise History of the X-15 Research Airplane (PDF). Monographs in Aerospace History. NASA. hdl:2060/20000068530. ISBN 0-16-050363-9. SP-2000-451. Archived (PDF) from the original on April 7, 2023. Price, A. B.; Martin Marietta (January 12, 1968). Thermal protection system X-15A-2 Design Report (PDF) (Technical report). NASA. hdl:2060/19680016245. CR-82003. Archived (PDF) from the original on August 30, 2023. Stillwell, Wendell H. (1965). X-15 Research Results - With a Selected Bibliography (PDF). NASA. SP-60. Archived (PDF) from the original on August 30, 2023. Watts, Joe D. (October 1968). Flight experience with shock impingement and interference heating on the X-15-2 research airplane (PDF) (Technical report). NASA. TM X-1669. Archived (PDF) from the original on 30 August 2023.

Illustrations

Worked examples

Example 1 — a first encounter with X-15 Flight 91

Start with the simplest possible case. Write down what X-15 Flight 91 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to X-15 Flight 91 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about X-15 Flight 91 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of X-15 Flight 91

In research: X-15 Flight 91 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses X-15 Flight 91 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: X-15 Flight 91 is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1963 in spaceflight, X-15 flights, so understanding it makes those chapters shorter.
In everyday life: Look for X-15 Flight 91 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study X-15 Flight 91 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what X-15 Flight 91 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain X-15 Flight 91 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is X-15 Flight 91 in simple terms?

Why does X-15 Flight 91 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study X-15 Flight 91?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on X-15 Flight 91.