Is there a car faster than a plane?
Supersonic speed is the speed of an object that exceeds the speed of sound (Mach 1). For objects traveling in dry air of a temperature of 20 °C (68 °F) at sea level, this speed is approximately 343.2 m/s (1,126 ft/s; 768 mph; 667.1 kn; 1,236 km/h). Speeds greater than five times the speed of sound (Mach 5) are often referred to as hypersonic. Flights during which only some parts of the air surrounding an object, such as the ends of rotor blades, reach supersonic speeds are called transonic. This occurs typically somewhere between Mach 0.8 and Mach 1.2.
Sounds are traveling vibrations in the form of pressure waves in an elastic medium. Objects move at supersonic speed when the objects move faster than the speed at which sound propagates through the medium. In gases, sound travels longitudinally at different speeds, mostly depending on the molecular mass and temperature of the gas, and pressure has little effect. Since air temperature and composition varies significantly with altitude, the speed of sound, and Mach numbers for a steadily moving object may change. In water at room temperature supersonic speed can be considered as any speed greater than 1,440 m/s (4,724 ft/s). In solids, sound waves can be polarized longitudinally or transversely and have even higher velocities.
Supersonic fracture is crack motion faster than the speed of sound in a brittle material.
Early meaning [ edit ]
At the beginning of the 20th century, the term «supersonic» was used as an adjective to describe sound whose frequency is above the range of normal human hearing. The modern term for this meaning is «ultrasonic».
Etymology: The word supersonic comes from two Latin derived words; 1) super: above and 2) sonus: sound, which together mean above sound, or faster than sound.
Supersonic objects [ edit ]
British Airways Concorde in early BA livery at London-Heathrow Airport, in the early 1980s
The tip of a bullwhip is thought to be the first object designed to break the sound barrier, resulting in the telltale «crack» (actually a small sonic boom). The wave motion travelling through the bullwhip is what makes it capable of achieving supersonic speeds.   However, the first man-made supersonic boom was likely caused by a piece of cloth, spurring the whip’s eventual development. 
Most modern firearm bullets are supersonic, with rifle projectiles often travelling at speeds approaching and in some cases  well exceeding Mach 3.
Most spacecraft are supersonic at least during portions of their reentry, though the effects on the spacecraft are reduced by low air densities. During ascent, launch vehicles generally avoid going supersonic below 30 km (~98,400 feet) to reduce air drag.
Note that the speed of sound decreases somewhat with altitude, due to lower temperatures found there (typically up to 25 km). At even higher altitudes the temperature starts increasing, with the corresponding increase in the speed of sound.
When an inflated balloon is burst, the torn pieces of latex contract at supersonic speed, which contributes to the sharp and loud popping noise.
Supersonic land vehicles [ edit ]
To date, only one land vehicle has officially travelled at supersonic speed, the ThrustSSC. The vehicle, driven by Andy Green, holds the world land speed record, having achieved an average speed on its bi-directional run of 1,228 km/h (763 mph) in the Black Rock Desert on 15 October 1997.
The Bloodhound LSR project planned an attempt on the record in 2020 at Hakskeenpan in South Africa with a combination jet and hybrid rocket propelled car. The aim was to break the existing record, then make further attempts during which [the members of] the team hope to reach speeds of up to 1,600 km/h (1,000 mph). The effort was originally run by Richard Noble who was the leader of the ThrustSSC project, however following funding issues in 2018, the team was bought by Ian Warhurst and renamed Bloodhound LSR. Later the project was indefinitely delayed due to the Covid-19 pandemic and the vehicle was put up for sale.
Supersonic flight [ edit ]
Main article: Supersonic aircraft
Most modern fighter aircraft are supersonic aircraft. No modern-day passenger aircraft are capable of supersonic speed, but there have been supersonic passenger aircraft, namely Concorde and the Tupolev Tu-144. Both of these passenger aircraft and some modern fighters are also capable of supercruise, a condition of sustained supersonic flight without the use of an afterburner. Due to its ability to supercruise for several hours and the relatively high frequency of flight over several decades, Concorde spent more time flying supersonically than all other aircraft combined by a considerable margin. Since Concorde’s final retirement flight on November 26, 2003, there are no supersonic passenger aircraft left in service. Some large bombers, such as the Tupolev Tu-160 and Rockwell B-1 Lancer are also supersonic-capable. The aerodynamics of supersonic aircraft is simpler than subsonic aerodynamics because the airsheets at different points along the plane often cannot affect each other. Supersonic jets and rocket vehicles require several times greater thrust to push through the extra aerodynamic drag experienced within the transonic region (around Mach 0.85–1.2). At these speeds aerospace engineers can gently guide air around the fuselage of the aircraft without producing new shock waves, but any change in cross area farther down the vehicle leads to shock waves along the body. Designers use the Supersonic area rule and the Whitcomb area rule to minimize sudden changes in size.
The sound source has now broken through the sound speed barrier, and is traveling at 1.4 times the speed of sound, c (Mach 1.4). Because the source is moving faster than the sound waves it creates, it actually leads the advancing wavefront. The sound source will pass by a stationary observer before the observer actually hears the sound it creates.
Conical shockwave with its hyperbola-shaped ground contact zone in yellow
However, in practical applications, a supersonic aircraft must operate stably in both subsonic and supersonic profiles, hence aerodynamic design is more complex. The main key to having low supersonic drag is to properly shape the overall aircraft to be long and thin, and close to a «perfect» shape, the von Karman ogive or Sears-Haack body. This has led to almost every supersonic cruising aircraft looking very similar to every other, with a very long and slender fuselage and large delta wings, cf. SR-71, Concorde, etc. Although not ideal for passenger aircraft, this shaping is quite adaptable for bomber use.
See also [ edit ]
- Area rule
- Hypersonic speed
- Sonic boom
- Supersonic aircraft
- Supersonic airfoils
- Transonic speed
- Vapor cone
- Prandtl–Glauert singularity
References [ edit ]
- ^«APOD: 2007 August 19 — A Sonic Boom». antwrp.gsfc.nasa.gov.
- «F-14 CONDENSATION CLOUD IN ACTION». www.eng.vt.edu. Archived from the original on 2004-06-02.
- Mike May (2002). «Crackin’ Good Mathematics». American Scientist. 90 (5). Archived from the original on 2016-03-22 . Retrieved 2015-08-26 .
- «Hypography – Science for everyone – Whip Cracking Mystery Explained». Archived from the original on 2012-02-17 . Retrieved 2008-02-06 .
- «Does the Tip of a Snapped Towel Travel Faster Than Sound?».
- «Hornady Ammunition Charts» (PDF) . Archived from the original (PDF) on 2007-09-27 . Retrieved 2011-11-04 .
External links [ edit ]
- «Can We Ever Fly Faster Speed of Sound», October 1944, Popular Science one of the earliest articles on shock waves and flying the speed of sound
- «Britain Goes Supersonic», January 1946, Popular Science 1946 article trying to explain supersonic flight to the general public
- MathPages — The Speed of Sound
- Supersonic sound pressure levels
15 reasons trains are better than planes
Travel involves so many choices — where, when and how to get there for starters. We’ve got “how to go” covered, and you can probably guess it doesn’t involve flying.
The following are 15 reasons we’re highlighting to show why travelling by train beats taking the plane:
1. Travel centre to centre
Airports are often located far outside the city centre. For example, travelling from central London to Stansted Airport takes well over an hour and can be expensive. On the other hand, train stations are normally centrally located. Take the rail journey from London to Edinburgh as an example: it’s 4 hrs and 30 mins from Kings Cross station to Edinburgh Waverley station, both located in their respective city centres. If you add in travel to and from London and Edinburgh airport, flying isn’t any faster than taking the train.
2. Train travel gives you leg room
Our own research has revealed that taking the train gives passengers more space on average than other common forms of transport including, of course, planes. Kick back and get comfy because there’s more room on average than other forms of transport.
3. Avoid airport security
Airport security lines can be long and stressful, and that 2 hr pre-flight arrival adds significant travel time. Train travel wins the speed prize in this race. For most internal UK rail services, such as Edinburgh to London, there’s no need to arrive at the station more than 15 mins before departure. Eurostar check-in for passengers with Standard Class and Standard Premier tickets closes 30 mins before departure, whilst Business Premier passengers only need to check in 10 mins early.
4. The environment
Air travel is now one of the fastest growing contributors to climate change. The aviation industry is said to contribute between 4 and 9% of the total climate change impact of humans. This means that choosing not to fly is a powerful pro-environmental action that helps you shrink your carbon footprint.
Eurostar commissioned independent research that assessed the CO2 per passenger produced by a London to Paris Eurostar journey compared to a London to Paris flight. The research looked at Eurostar passenger loadings and power consumption, and how Eurostar’s electricity is generated. The research then compared these with aircraft loadings and fuel consumption. The staggering conclusion was that choosing the train over flying cuts CO2 emissions per passenger by 90%.
5. The dining car
There are no salt-laden, half frozen airplane meals here. In fact, some trains in Europe have top class regional and local cuisine on board. In the UK, GWR serves top quality food in their ‘Pullman Dining Car’. Rail operators are increasingly trying to cater to various dietary needs as our ‘Veganuary’ research discovered.
6. Eat and drink from your own menu
On the other hand, if you don’t feel like spending money buying food on board, you can bring your own along. Travellers are always allowed to take their own pre-packed food and drink on board trains across Europe, so pack a picnic (Pro tip: don’t want to leave a pile of disposable plastic in your wake? Learn how in our top train travel hacks and packs).
7. Get free stuff with your train tickets
Loads of train tickets include hidden freebies and discounts in major towns and cities, so get clued up:
2-for-1 entry to hundreds of tourist attractions such as London Zoo, Madame Tussauds, The London Eye and many ore around the UK.
2-for-1 tickets for the best museums in Paris, Brussels, Lille, Lyon and Marseille with your Eurostar ticket.
25% discount for Venice museum pass for ticket holders for any of Italy’s high-speed Frecce trains
8. See more, learn more
Train travel can be a truly romantic and fascinating way to travel. Travel through different places and gaze out your window upon varied landscapes and culture. Castles, vineyards, villages, the Alps, Rhine falls. There’s so much to see and trains traverse all of it.
9. Stay connected
No flight-mode, reliable mobile phone coverage and almost all modern trains have plug-sockets at your seat. Many trains also now have wifi coverage so it’s easy to work, stay updated on social media and post live train selfies of your journey.
10. The tactical switch
If your neighbour is not your ideal travel companion, you have a better chance of switching to a different seat. When there’s unreserved seating on services that aren’t packed, you’ll often be able to move around as you please. There are also no seatbelt signs to keep you tied down.
11. No turbulence
Avoid those nerve-jangling movements associated with flying by staying on track.
12. Travelling with children is easy
Trains offer greater flexibility at each stage of the journey, making family train travel easier and less stressful than flying. Children can move around more freely than on a plane, and you’ll have the space to pack home comforts. Even better, many rail operators permit young children (up to four years old) to travel for free if they share a seat with an adult passenger. When you book with us, we’ll prompt you to enter the age of child passengers and automatically assign suitable tickets.
13. Breaking up your journey can be a real bonus
Heading to the south of Italy and fancy stopping over in Milan for lunch? Trains allow you to do exactly that. Stretch your legs on a walk around Paris or take in a museum in London, you can schedule convenient stopovers to make the most of your itinerary.
14. Baggage isn’t a bother
Riding the rails also means that you’re freer to pack what you want, as luggage restrictions are more flexible than on planes.
15. Trains are more pet and bike friendly
Indeed, it’s far easier to bring pets and bikes on trains than on planes, though you’ll need to check with your rail operator to be safe. Our help guides are a great place to start.