50 Fun Facts About Aerospace Engineering

What colour are aircraft flight recorders, the so-called black boxes, painted to make them easier to find?

Bright orange paint makes the recorders stand out in wreckage, and an underwater locator beacon pings to guide searchers if an aircraft goes down at sea.

What did Orville and Wilbur Wright repair, sell and manufacture in Dayton, Ohio, before they built aircraft?

Bicycles left their mark on the 1903 Flyer, whose propellers were turned by chains like a cycle's. Wilbur hit on twisting the wings for control while idly flexing an inner-tube box.

What are the long white contrails that form behind high-flying jet airliners mainly made of?

Ice crystals form when water vapour in the engine exhaust freezes in the bitter cold of cruising altitude, which makes a contrail a long, thin artificial cloud.

Which gas are airliner tyres filled with instead of ordinary air, cutting the risk of an explosion if they overheat?

Nitrogen is inert, so it cannot feed a fire. Regulators required it after oxygen in air-filled tyres reacted with gases given off by overheated rubber and exploded.

Which of Isaac Newton's laws explains how a rocket is pushed forward by gas rushing out behind it?

The third law pairs every action with an equal and opposite reaction, so a rocket needs nothing to push against and works even in the vacuum of space.

Which huge part of the Space Shuttle launch stack was thrown away on every flight instead of being reused?

The external tank was jettisoned seconds after main engine cut-off and fell back into the atmosphere. From the third mission it was left unpainted, which saved about 272 kg.

Which American test pilot first broke the sound barrier, flying the rocket-powered Bell X-1 over California in 1947?

Chuck Yeager made the flight with two ribs broken in a riding fall two nights earlier, in an aircraft he had named Glamorous Glennis after his wife.

Which supersonic airliner, retired in 2003, had a nose that drooped so its pilots could see the runway when landing?

Concorde also grew in flight: its airframe became so hot at cruising speed that the fuselage expanded by as much as 300 mm.

Which Soviet satellite, a polished metal sphere with four antennas, was the first artificial object to orbit Earth?

Sputnik 1 did little more than broadcast radio pulses, falling silent after three weeks when its batteries ran down, yet it triggered the start of the Space Race.

Which force acts opposite to an aircraft's direction of travel and must be overcome by thrust?

Drag climbs with the square of speed in fast flight, so doubling an aircraft's airspeed roughly quadruples the resistance its engines must beat.

What do pilots call the sudden loss of lift when a wing's angle of attack exceeds its critical angle?

A stall has nothing to do with the engine: the airflow separates from the wing's upper surface, typically once the angle passes about 15 degrees.

Which hinged control surfaces on the trailing edge of each wing are used in pairs to roll an aircraft?

Ailerons take their name from the French for 'little wing', a word also used for the tips of a bird's wings that steer its flight.

Which thin region of slowed air next to a wing's surface did Ludwig Prandtl first describe in 1904?

The boundary layer let engineers confine friction to a thin skin of air and neglect it everywhere else, which tamed flow equations that had been too hard to solve.

Which term describes an aircraft's nose tilting up or down, one of three rotations alongside roll and yaw?

Pitch is rotation about an axis running from wing to wing, and pilots control it with the elevators, usually found on the tail.

Which ratio, named after an Austrian physicist, compares an aircraft's speed with the local speed of sound?

Mach number honours Ernst Mach, who photographed the invisible shock waves around projectiles flying faster than sound. A Swiss engineer proposed the name in 1929.

Which Swiss mathematician's 1738 book Hydrodynamica set out the principle linking faster fluid flow to lower pressure?

Daniel Bernoulli had a rival at home: his father Johann allegedly lifted the book's key ideas for a work of his own and backdated it to appear first.

Which test device did the Wright brothers build in 1901 to measure the lift of dozens of miniature wings?

A wind tunnel six feet long gave the Wrights more accurate data than anyone had before, after poor glider flights made them doubt the published lift figures.

What are the upturned tips fitted to many airliners to save fuel by weakening the vortices trailing behind called?

Winglets took their modern form in the 1970s, when NASA engineer Richard Whitcomb refined the idea in response to the leap in fuel costs after the 1973 oil crisis.

Which wing planform is shared by the Avro Vulcan bomber and the Dassault Mirage III fighter?

Delta wings are named for their likeness to the triangular Greek capital letter. The shape is simple and fairly cheap to build, a big factor in the Mirage's success.

Which term do engineers use for flight at more than roughly five times the speed of sound?

Hypersonic flight is fast enough to change the air itself: in the heat around the vehicle, molecules break apart and become electrically charged.

Which type of jet engine, sending most of its air around the core, powers almost all jet airliners?

Turbofan engines use a turbine to drive a large ducted fan, and the air that bypasses the core is what makes them quieter and more economical than a pure jet.

Which jet engine component sprays extra fuel into the hot exhaust to give fighter aircraft a brief surge of thrust?

Afterburner use is kept to short periods because it sharply increases fuel consumption. British engineers know the same system as reheat.

Which Royal Air Force officer patented the jet engine in 1930, years before any jet aircraft had flown?

Frank Whittle let the patent lapse in 1935: he could ill afford the £5 renewal fee, and the Air Ministry refused to pay it for him.

Which engine, burning its fuel in a supersonic airflow, drove NASA's X-43A to nearly ten times the speed of sound?

Scramjet is short for supersonic combustion ramjet. On the X-43A's 2004 record flights the engine ran for only about ten seconds before the craft glided into the ocean.

Which fuel, also widely burned for cooking and lighting, is the basis of airliner jet fuels such as Jet A-1?

Kerosene makes a safe jet fuel, with a flash point above 38 °C, and a highly refined grade called RP-1 also powers some rocket engines.

Which fuel did the Space Shuttle's three main engines burn, leaving an exhaust made almost entirely of water vapour?

Liquid hydrogen does a second job before it burns: the bitterly cold fuel is first piped around the engine nozzle to cool it.

What is the technique of discarding empty sections of a rocket during ascent, so less dead weight is carried, called?

Staging is what makes orbit reachable: the speed required demands a higher ratio of propellant to structure than any single rocket has achieved.

Which American physicist launched the world's first liquid-fuelled rocket from a Massachusetts farm in 1926?

Robert Goddard was mocked in a New York Times editorial in 1920. The paper printed a correction 49 years later, the day after Apollo 11 lifted off for the Moon.

Which German-born engineer was chief architect of the Saturn V rocket that sent Apollo crews to the Moon?

Wernher von Braun had co-developed the wartime V-2 missile before being moved secretly to the United States under Operation Paperclip.

Which self-taught Russian schoolteacher set out the mathematics of rocket travel in a landmark work of 1903?

Tsiolkovsky lost his hearing to scarlet fever at nine and educated himself. Inspired by the Eiffel Tower, he was also the first person to conceive a space elevator.

What is the minimum speed needed to break free of a planet's pull, about 11.2 km per second for Earth, called?

Escape velocity is rarely reached in one sprint: moving that fast through thick air near the ground would burn most objects up or tear them apart.

Which kind of orbit, about 35,786 km above the equator, keeps a satellite fixed over one spot on Earth?

Geostationary satellites were popularised by science fiction author Arthur C. Clarke, whose 1945 magazine article proposed using them as worldwide radio relays.

Which threshold 100 km above sea level does the world air sports federation use to mark the edge of space?

The Kármán line honours Theodore von Kármán, who calculated that aeroplane flight had a theoretical ceiling of about 84 km. The rounder figure was settled on later.

Which manoeuvre let the Voyager probes pick up speed by swinging past Jupiter and Saturn without burning fuel?

Gravity assist turned a rare line-up of the outer planets in the late 1970s into a grand tour, letting a single probe go on to visit Uranus and Neptune as well.

Which fuel-saving manoeuvre, named after a German scientist, uses two engine burns to move between orbits?

Hohmann transfer timing is why Mars missions depart in clusters: the two planets line up for the trip only once every 26 months.

Which engine, used by NASA's Dawn probe, makes a gentle but highly efficient push by firing out charged xenon atoms?

An ion thruster pushes very gently, about as hard as a sheet of paper weighs on the Deep Space 1 probe, yet it runs for so long that the speed gained is enormous.

What do launch engineers call the moment when aerodynamic pressure on a climbing rocket reaches its peak?

Max Q is why rockets often throttle down partway through the climb: the Space Shuttle eased its main engines back to about 65–72% of rated thrust.

Which measure of rocket engine efficiency, quoted in seconds, shows how much push each unit of propellant gives?

Specific impulse has a handy quirk: stated as a time, it comes out as the same number whether engineers work in metric or imperial units.

What are the five positions where a spacecraft can hold steady relative to two larger orbiting bodies called?

Lagrange points include L2, about 1.5 million km from Earth, where the James Webb Space Telescope circles in a halo orbit.

Which Soviet engineer, known publicly only as the Chief Designer, ran the programme that sent Yuri Gagarin into space?

Sergei Korolev was kept anonymous partly for fear of assassination. Years earlier he had been sent to a Gulag camp in Siberia, where he laboured in a gold mine.

Which American designer championed the flying wing in the 1940s, decades before the similar B-2 stealth bomber flew?

Jack Northrop was cleared, shortly before his death, to hold a scale model of the secret B-2, which has the same 172-foot wingspan as his YB-49 bomber.

Which Lockheed spy plane, built mostly of titanium, cruised at more than three times the speed of sound?

SR-71 Blackbird builders had to wash welded parts in distilled water, because the chlorine in ordinary tap water corroded the exotic airframe.

What is the nickname of Lockheed's secretive advanced projects division, builder of the U-2 and F-117?

Skunk Works took its name from a foul-smelling backwoods factory in the comic strip Li'l Abner, which was hugely popular when the unit was set up.

Which British jump jet could take off and land vertically thanks to four swivelling engine nozzles?

Harrier pilots also relied on small reaction nozzles in the nose, tail and wingtips, which kept the aircraft balanced while it hovered.

Which lightweight material makes up about half of the Boeing 787 Dreamliner's airframe by weight?

Carbon-fibre composite does not corrode, so the Dreamliner's cabin air can be kept far more humid than in older aluminium airliners.

Which structural failure, brought on by repeated cabin pressurisation, broke up two de Havilland Comet jetliners?

Metal fatigue was pinned down by submerging a whole Comet fuselage in a purpose-built water tank and pressurising it again and again until it cracked.

Which small booster part, stiffened by a freezing launch morning, failed and destroyed Space Shuttle Challenger?

An O-ring sample starred in a televised hearing when physicist Richard Feynman clamped it, dipped it in a glass of cold water and showed it had lost its spring.

Which digital control system, replacing mechanical linkages, did the Airbus A320 pioneer among airliners?

Fly-by-wire lets flight computers interpret the pilot's side-stick commands and hold the aircraft inside safe limits, a safeguard called flight envelope protection.

Which forward-facing probe, named after a French engineer, measures airspeed from the pressure of oncoming air?

Pitot tube design began with water, not air: Henri Pitot invented the device in 1732 while he was working on aqueducts.

Which NASA mathematician, portrayed in Hidden Figures, checked the computer's sums for John Glenn's orbital flight?

Katherine Johnson was asked for by name: Glenn refused to fly unless she personally verified the numbers from NASA's new electronic computers.