Is it possible to travel from New York to Los Angeles in just 12 minutes?

Some flights are so swift that attendants barely have time to serve drinks, while others last long enough to fit in dinner, a few movies, and a full night’s rest. Imagine traveling from New York to Tokyo in just 90 minutes—would you risk the worst jet lag ever to make the trip faster than going through airport security?

These were the thoughts that crossed our minds as we read about the second test flight of the Falcon Hypersonic Technology Vehicle (HTV-2), a U.S. DARPA aircraft designed to fly at speeds of Mach 20, or 20 times the speed of sound.

The Lockheed Martin HTV-2 wasn't a commercial airliner or even a fighter jet, but an unmanned, rocket-launched prototype for hypersonic technology. The data collected from this flight is helping the Pentagon develop Prompt Global Strike aircraft, capable of reaching targets anywhere in the world in 60 minutes or less. Think of them as unmanned, rocket-powered versions of cruise missiles, or perhaps the violent counterparts of Domino's pizza delivery drivers (no refunds for late deliveries) [sources: DARPA; Weinberger].

Unfortunately, DARPA's second HTV-2 test, like the first, began with a loss of contact and ended with the vehicle self-destructing as it plunged into the Pacific Ocean [sources: AFP; Pappalardo]. In a twist of good news and bad, DARPA succeeded in improving aerodynamic stability from the first test, only to see unexpected turbulence tear off large sections of the craft's exterior during the second [sources: DARPA; Ferran].

What does this mean for the future of commuting, especially for those more interested in business meetings than missile strikes? The answer is unclear. As of November 2012, several companies, including heavyweights like Boeing and European Aeronautic Defence and Space Company N.V. (EADS), the parent company of Airbus, as well as emerging players like XCOR and HyperMach, have expressed interest in filling the gap left by the Concorde. Meanwhile, Virgin Galactic and Sierra Nevada Space Systems continue their focus on suborbital spaceplane development.

Despite their marketing claims, most of these vehicles are supersonic rather than hypersonic, and for good reason. Surpassing Mach 5, the threshold that separates supersonic from hypersonic, presents challenges in the form of chaotic atmospheric physics.

SCRAMbled Physics

The second trial of the now-obsolete HTV-2 highlights the brutal challenges of hypersonic flight. Even the Concorde, which reached a supersonic speed of 1,350 mph (2,172 kph), was retired after 27 years because of safety risks and financial concerns [source: Pappalardo].

Physics can be unforgiving. As a plane nears the speed of sound, the air resists its motion, compressing into a wall that the plane must break through. At these high speeds, drag, lift, and combustion become unpredictable, and adaptations like delta wings and ramjets—engines that compress air using the plane's forward momentum—can range from inefficient to ineffective at slower speeds [sources: Darling; NASA].

Hypersonic aircraft require even more specialized solutions, such as ablative heat-resistant armor and supersonic combustion ramjets (scramjets) for propulsion [sources: Darling; NASA]. At hypersonic speeds (Mach 5-10), air molecules turn into electrically charged plasma, which creates exothermic reactions that compound the intense heat from friction [sources: Fletcher; NASA].

To travel from New York to Los Angeles in just 12 minutes would require flying 22 times faster than a commercial jet. At these extreme speeds, the aircraft doesn't glide through the air—it rips through it, generating immense pressure and temperatures up to 3,500°F (1,900°C). While supersonic jets have sharp, streamlined designs, hypersonic planes need a more rounded shape to help dissipate heat, similar to the shape of an Apollo command module. Maneuvering at such speeds is a challenge, requiring precise sensors and almost instantaneous reactions [sources: DARPA; Fletcher; NASA].

Introducing passengers into the equation adds significant complexity. It's hard to imagine a passenger plane that would be aerodynamically compatible with hypersonic flight. Furthermore, any aircraft capable of achieving this would need to accelerate gradually, rather than rapidly, to avoid the risk of passengers being crushed during takeoffs, landings, and turns.

A human body can endure a force of 2-3 G's (two to three times Earth's gravity) for an extended period, particularly when moving forward. However, don't expect any high-paying passenger to tolerate even 1 G of acceleration for more than a few minutes. Still, such forces may be unavoidable: To reach hypersonic speeds, aircraft might need specialized equipment that makes them cumbersome at slower speeds. This could mean the use of rocket boosters, and the resulting G-forces, to achieve the necessary altitude and velocity for flight [sources: NASA; Zuidema et al.].

The design requirements for a true hypersonic plane, especially one capable of reaching Mach 20, likely won't align with the comfort and safety standards of a typical passenger jet. However, if the predictions are to be believed, hypersonic vehicles are poised to dominate both military and civilian air travel in the near future.

Hypersonic: Don't Believe the Hype

Hypersonic passenger jets — and the dream of one-hour flights from New York to London — have been discussed for nearly 60 years. The real question isn't whether a military or private aircraft will make this a reality, but when — or if — ordinary travelers like Joe and Jane Carryon will ever board one.

During his 1986 State of the Union address, U.S. President Ronald Reagan proposed the creation of an 'Orient Express,' a plane capable of traveling from New York to Tokyo in just two to three hours. The project for the Rockwell X-30, a passenger space liner designed for single-stage-to-orbit (SSTO), was scrapped before it could reach the prototype stage [source: Sanger].

Supersonic travel could make a comeback, but it’s unlikely to happen anytime soon. One potential project under development in 2012 is the Zero Emission Hypersonic Transportation (Zehst) system, a craft powered by seaweed biofuel, developed through a collaboration between EADS and Japan. Expected to be launched sometime between 2040 and 2050, Zehst will fly at double the speed and altitude of the Concorde, with ticket prices around €6,000 ($8,500) [sources: Jones; Wall].

If successful, Zehst will transport 50-100 passengers from Paris to Tokyo in just 2.5 hours, compared to the current 11-hour flight time. The craft will utilize three propulsion systems: two turbofans for the initial climb to Mach 0.8, followed by two rocket boosters that will accelerate it to Mach 2.5. Once it reaches Mach 4, ramjets will take over, and as it nears its destination, the plane will glide in, with the turbofans re-engaging for landing [source: Wall].

Boeing, Airbus' primary competitor, shifted from its supersonic Sonic Cruiser to the subsonic 787 Dreamliner, but it's far from out of the high-speed aircraft game. With military contracts keeping it in the race, the technology behind Boeing's X-51A WaveRider—capable of flying on its own shock wave and achieving speeds over Mach 5—could potentially lay the groundwork for future space or commercial applications [sources: Bartkewicz; Boeing].

Meanwhile, European aerospace company HyperMach has unveiled its SonicStar, a plane designed to eliminate sonic booms while flying twice the speed of Concorde. SonicStar is expected to cruise at Mach 3.6, at an altitude of 60,000 feet (18,300 meters), and carry 10-20 passengers between New York and Dubai in just two hours and 20 minutes. HyperMach aims to have the plane operational by June 2021 [source: Jones].

XCOR, a California-based aerospace company, is advancing the Lynx, a commercial aircraft designed for suborbital flight. This two-seat vehicle aims to achieve speeds greater than 2,500 mph (4,000 kph) and reach altitudes of 62 miles (100 kilometers). After reaching such heights, Lynx will descend to reduce atmospheric drag, friction, and turbulence, offering a more efficient flight experience [source: Waldron].

Considering all factors, swapping the idealistic vision of hypersonic travel for a more feasible form of hyperbolic flight may prove to be a more practical solution.

The Suborbital Shuffle

The challenge with fast flight is that disturbances, such as turbulence, can only spread so quickly through a fluid like air. When speeds reach or surpass a certain threshold, it becomes less like gliding through water and more like crashing into it from a great height. To avoid this battle, some opt to skip the atmosphere entirely and instead make suborbital hops that skim the edge of space.

Space planes – fully reusable spacecraft capable of flying in both space and Earth's atmosphere – and high-altitude commercial hoppers have experienced a resurgence with the rise of the commercial spaceflight industry. Ideally, these vehicles would take off and land from runways, though for now, they remain more of a distant dream. Just as subsonic, supersonic, and hypersonic designs excel in their respective flight regimes, the propulsion and control systems for atmospheric flight differ from those used in space. Consequently, most designs follow a two-stage approach, where the craft is carried aloft by a 'mother ship' airplane or rocket before activating its own flight systems.

For instance, Richard Branson's Virgin Galactic aims to send passengers to the edge of space (about 62 miles or 100 kilometers up) on SpaceShipTwo, a 60-foot (18-meter), six-passenger rocket glider suspended beneath the VirginMothership Eve. When the dual-fuselage carrier reaches 50,000 feet (15,240 meters), SpaceShipTwo detaches, glides back toward Earth, and uses a special 'feathering' drag technique to slow its re-entry [source: Chang]. Virgin Galactic has also entered into a partnership with Sierra Nevada Space Systems, possibly to offer bookings for space flights aboard its planned Dream Chaser spacecraft [source: Chang].

The Dream Chaser is a reusable mini-shuttle based on the Soviet Union's now-defunct Bor-4 space shuttle design. It will be launched by an Atlas V rocket and land like an airplane. Sierra Nevada plans to collaborate with space agencies to transport up to seven astronauts and cargo between Earth and the International Space Station (ISS) [source: Chang]. In August 2012, the project secured $212.5 million from NASA's Commercial Crew Integrated Capability (CCiCap) program to further its development [source: Sierra Nevada].

Space planes may need commercial passengers to stay competitive in the space delivery race. For example, SpaceX successfully delivered cargo to the ISS in October 2012 using a traditional rocket-and-capsule approach. Orbital Sciences Corp., which had been developing a space plane, shifted to a non-reusable rocket system for its planned ISS supply missions after the space plane project lost NASA funding [source: Orbital].

Supersonic, hypersonic, or even suborbital flights that soar at extreme altitudes might represent the future of air travel. However, only time will reveal if – or when – they will become a reality.