Mile per hour to Mach number Converter

What is a sonic boom?

When an object travels faster than sound (Mach 1+), it creates pressure waves faster than they can propagate away. These waves pile up, forming a shock wave—a cone of intense pressure that trails the object like the wake of a boat.

The "Boom":

• When this cone passes over you, you hear a sharp double "boom-boom"
• First boom: nose shock wave
• Second boom: tail shock wave
• Sounds like thunder or an explosion
• Can rattle windows, set off car alarms

Damage Potential:

• Low-altitude supersonic flight: Can break windows, damage structures
• High-altitude supersonic flight: Boom reaches ground weakened, sounds like distant thunder
• Concorde cruised at 60,000 feet to minimize ground impact

Continuous: The sonic boom is continuous along the entire flight path, not just when "breaking" the barrier. Everyone below the flight path hears a boom as the cone passes over them.

Why did the Concorde stop flying?

Economic and Regulatory Challenges:

1. Sonic Boom Restrictions:

• Banned from supersonic flight over most land masses
• Limited to oceanic routes (transatlantic primarily)
• Reduced potential markets dramatically

2. Fuel Consumption:

• Burned 3x more fuel than subsonic jets per passenger
• 17 tons per hour at Mach 2 cruise
• Rising fuel costs made operation increasingly expensive

3. Limited Capacity:

• Only 92-120 passengers (vs 400+ on Boeing 747)
• Small market for ultra-premium tickets
• Round-trip London-New York: $12,000+ (1990s-2000s)

4. Maintenance Costs:

• Complex systems required extensive maintenance
• Only two operators (British Airways, Air France)
• No economies of scale

5. Air France Flight 4590 Crash (2000):

• Metal debris on runway punctured tire
• Debris hit fuel tank, caused fire
• 113 killed
• Led to temporary grounding, increased insurance costs
• Public confidence damaged

Final Flight: October 24, 2003 (British Airways)

Modern Revival Attempts: Companies like Boom Supersonic developing new supersonic airliners with quieter "boom" and better fuel efficiency. Target: 2029-2030 service entry.

Can a car go Mach 1 on land?

Yes—but only one has officially done it.

ThrustSSC (1997):

• Speed: 763 mph (Mach 1.016) on October 15, 1997
• Location: Black Rock Desert, Nevada
• Driver: Andy Green (Royal Air Force fighter pilot)
• Power: Two Rolls-Royce Spey jet engines (from Phantom fighter jets)
• Thrust: 110,000 lb (50,000 kg)
• Weight: 10.5 tons
• First land vehicle to create sonic boom

Challenges:

• Extreme instability at transonic speeds
• Required perfect desert surface (dry lake bed)
• Aerodynamic design critical (shaped like a fighter jet)
• Braking from 760 mph without flipping

Bloodhound LSR (In Progress):

• Target: 1,000 mph (Mach 1.3)
• Hybrid jet + rocket propulsion
• Same driver (Andy Green)
• Testing ongoing in South Africa

What is "Critical Mach Number"?

Critical Mach Number (Mcrit) is the speed at which airflow over any part of the aircraft first reaches Mach 1—even if the aircraft itself is flying slower than Mach 1.

Why This Happens:

• Air accelerates as it flows over the curved upper surface of wings
• Example: Aircraft flying at Mach 0.80, but airflow over wing reaches Mach 1.0

Consequences of Exceeding Mcrit:

• Shock waves form on wing surface
• Airflow separation behind shock waves
• Loss of lift (buffeting, "Mach tuck")
• Increased drag (transonic drag rise)
• Control problems

Typical Values:

• Straight wing aircraft: Mcrit ≈ 0.75-0.85
• Swept wing aircraft: Mcrit ≈ 0.85-0.92
• Supersonic fighters: Mcrit > 0.95

Maximum Mach Number (MMO):

• Regulatory limit for aircraft (e.g., MMO = 0.90 for Boeing 737)
• Pilots must not exceed this speed

How do pilots calculate Mach number?

Instrumentation:

1. Machmeter (Cockpit Instrument):

• Combines pitot-static pressure measurements with temperature
• Directly displays Mach number
• Standard on all jet aircraft

2. Flight Management System (FMS):

• Computer calculates Mach number continuously
• Uses air data sensors (pitot tubes, static ports, temperature probes)
• Displays on primary flight display

Manual Calculation: $$ M = \frac{TAS}{LSS} $$

Where:

• TAS = True Airspeed (from airspeed indicator + altitude + temperature correction)
• LSS = Local Speed of Sound = 38.94 × √T (where T is temperature in Kelvin)

Example:

• Altitude: 35,000 feet
• Temperature: -57°C = 216 K
• TAS: 487 knots
• LSS: 38.94 × √216 = 38.94 × 14.7 = 573 knots
• Mach: 487 ÷ 573 = Mach 0.85

Is Mach 10 possible for aircraft?

Yes—but extremely challenging.

Achieved (Unmanned):

• NASA X-43A (2004): Mach 9.6 (7,000 mph) for 10 seconds
• Scramjet (supersonic combustion ramjet) technology
• Hydrogen fuel
• Launched from B-52 bomber + rocket booster
• Unmanned test vehicle

Challenges at Mach 10:

1. Extreme Heat:

• Air friction generates 3,000°F+ surface temperatures
• Requires exotic materials (carbon-carbon composites, ceramics)
• Active cooling systems needed

2. Engine Technology:

• Turbojets don't work above ~Mach 3 (air too fast for compressor)
• Ramjets work Mach 3-6 (no moving parts)
• Scramjets needed above Mach 6 (air stays supersonic through engine)
• Very low thrust-to-weight ratio

3. Control:

• Hypersonic flight extremely unstable
• Milliseconds to react
• Requires autonomous flight control systems

Current Applications:

• Hypersonic missiles: Russia (Kinzhal, Avangard), China (DF-ZF), US (under development)
• Space access: Potential for single-stage-to-orbit vehicles
• Research: NASA X-51 Waverider (Mach 5.1 sustained, 2013)

What is the fastest Mach number ever achieved?

By Manned Aircraft:

• SR-71 Blackbird: Mach 3.3 (2,193 mph) sustained cruise
• X-15 rocket plane: Mach 6.72 (4,520 mph) in 1967—still holds record

By Unmanned Aircraft:

• NASA X-43A: Mach 9.6 (7,000 mph) in 2004

By Spacecraft:

• Space Shuttle re-entry: Mach 25 (17,500 mph)
• Apollo 10 (1969): Mach 36 (24,791 mph)—fastest manned vehicle ever
• Parker Solar Probe: Mach 550+ (430,000 mph relative to Sun)—fastest human-made object

By Natural Objects:

• Meteors: Mach 50-200+ entering atmosphere

Why do some fighter jets have "supercruise"?

Supercruise is the ability to fly supersonic (Mach 1+) without using afterburners.

Traditional Supersonic Flight:

• Requires afterburner (raw fuel sprayed into exhaust, ignited)
• Increases thrust 40-70%
• Burns 3-5x more fuel
• Can only sustain for minutes

Supercruise Advantages:

• Fuel efficiency: Supersonic cruise without afterburner
• Extended supersonic duration: Hours instead of minutes
• Lower heat signature: Harder to detect with infrared missiles
• Greater range: Less refueling needed

Aircraft with Supercruise:

• F-22 Raptor: Mach 1.8 supercruise
• Eurofighter Typhoon: Mach 1.5 supercruise
• Dassault Rafale: Mach 1.4 supercruise
• Concorde: Mach 2.04 supercruise (civilian application)

How It's Achieved:

• Extremely efficient engines (high bypass turbofans with afterburner)
• Aerodynamic design minimizing supersonic drag
• High thrust-to-weight ratio

How loud is a sonic boom?

Loudness varies by altitude and aircraft size:

Concorde:

• At 60,000 feet cruise: 100-110 decibels on ground (sounds like distant thunder)
• At 40,000 feet: 120+ decibels (can break windows)

Fighter Jet:

• Low-altitude supersonic pass: 130-140 decibels (painfully loud, like artillery)
• High-altitude: 90-100 decibels (loud but not painful)

Comparison:

• Normal conversation: 60 dB
• Lawn mower: 90 dB
• Rock concert: 110 dB
• Jet engine (close): 140 dB
• Gunshot: 160 dB

Perceived Impact:

• Overpressure: 1-2 pounds per square foot (psf) typical for Concorde at cruise altitude
• 5+ psf: Can break windows
• 10+ psf: Structural damage to buildings

Why Banned Over Land:

• Continuous disturbance along entire flight path
• Affects thousands of people per flight
• Disrupts wildlife
• Property damage lawsuits

Can shock waves be photographed?

Yes—through schlieren photography.

Technique:

• Uses light refraction to visualize air density gradients
• Invented by August Toepler (1864), refined by Ernst Mach (1887)
• Shock waves create sharp density changes = visible patterns

Modern Applications:

• Wind tunnel testing: Visualizing airflow over models
• Ballistics research: Photographing bullets in flight
• NASA testing: X-59 "quiet supersonic" aircraft development
• Airshows: Ground-based cameras capturing fighter jets' shock waves

Iconic Images:

• Ernst Mach's 1888 bullet shock wave photographs
• NASA's T-38 shock wave interaction photos
• Schlieren video of sonic booms passing over landscape

Smartphone Era:

• High-speed smartphone cameras can sometimes capture shock wave patterns from fighter jets with proper lighting conditions