Aircraft Catapult; An overview

choi

(1) Kahlon AS, Gupta T, Dahiya P and Chaturvedi SK, A Brief Review on Electromagnetic Aircraft Launch System, International Journal of Mechanical and Production Engineering (IJMPE), 5: 58 (2017).
www.iraj.in/journal/journal_file ... 150408975258-67.pdf

Note:
(a) Institute of Research and Journals (IRAJ), based in Bhubaneswar, Odisha, India
https://en.wikipedia.org/wiki/Odisha
, published IJMPE.
(b) First and foremost, go to Table 2 at page 63, where MJ is megajoule. The text is found in paragraph 5.2.1 (heading: "Higher Launch Energy"), which ended with three sentences: "After a successful launch it takes the steam accumulators nearly 80 seconds [I do not know how much water needs to be heated in that short period or how much heat is needed] to build up the pressure again for consecutive launches. This time period is significantly reduced by EMALS to about 45 seconds. A comparison of relative launch energies for different launch mechanism is depicted in the graph [ie, Table 2]."
(c)
(i) Then go to page 60 and read almost the entire page, starting with "IV. CATAPULT ASSISTED TAKE OFF BUT ARRESTED RECOVERY (CATOBAR)."  The acronym CATOBAR (noting words in the preceding quotation/ heading is nothing magical, denoting exactly what the quotation says.
(ii) Figure 1 on this page is explained in paragraph 4.2: "Before launching, the aircraft['s engine] is set to full throttle, carrier is steered against the wind as far as possible[.]"
(iii) Paragraph 4.2 continues on to page 61: "Towards the end of the run, the piston approaches the water break (used to stop the shuttle [steam catapult viewed as shuttle, each run constituting a shuttle]) and a switch is actuated which stops the flow of steam into the cylinder by closing the launch valves. At the same time the exhaust valves are opened for letting out the spent steam [so, for the next run or launch, water needs to be heated again to generate steam]."

(2) In Alamy, search term (steam catapult) -- no quotation marks -- returns many photos that is full of (spent) steam during the entire launch, not just at the end of launch. I do not know whether this is desirable or a leak.  
https://www.alamy.com/stock-photo/steam-catapult.html?imgt=0

(3) Now , return to (1) -- specifically page 60. Paragraph 4.1.1: "Compressed Air Catapult: The compressed air catapult is similar to Wright brothers gravity catapult with the weight being replaced by compressed air."
(a) Recall pellet gun also uses compressed air, by bending gun barrel toward stock. So, compressed air catapult was nothing magical.
(b) Wright Brothers
https://en.wikipedia.org/wiki/Wright_brothers
("They made the first controlled, sustained flight of a powered, heavier-than-air aircraft with the Wright Flyer [or Flyer I, powered by twin propellers (same as Flyer II); in English, proper spelling is 'flier'] on December 17, 1903, 4 mi (6 km) south of [present-day Town of] Kitty Hawk, North Carolina, at what is now known as Kill Devil Hills")

In this Wiki page, pay attention to
(i) A photo whose caption reads: "The modified 1905 Flyer at the Kill Devil Hills in 1908, ready for practice flights. Note there is no catapult derrick; all takeoffs were used with the monorail alone [biplane on monorail; hence no catapult]." That was 1908.
(ii) Another photo further down the page, with caption: "The Wright Model A Flyer flown by Wilbur 1908–1909 and launching derrick, France, 1909."


(c) How does the derrick -- or in (3) above, "gravity catapult" -- work?
(i) A picture is worth a thousand words. However, I found no graph or illustration that is illuminating. Then I found a video clip of the Brothers.

Wright Brothers Flight, 1908. New Zealand History (the words underneath it at the top of the Web page is Maui), undated
https://nzhistory.govt.nz/media/ ... s-first-flight-1903
("This British Pathé film clip shows the Wright Brothers flying in 1908. * * * The Wrights had developed [by 1903] a lightweight 25-horsepower engine which provided a much higher power to weight ratio than anything that had gone before. With this, and a little help on the launch site from a heavy lead weight*, they were airborne and away.
*The catapult technique was not used for the flights of 17 December 1903. On that occasion their aeroplane left the ground under its own power. The longest of the four flights that day was a shade under a minute, at 59 seconds")

At 1:45 of the video (which lasts 2:09 minutes) you will see the biplane, with the Brothers as copilots, launched by moving AWAY from the derrick. Of course, this is the way it should be: The biplane could not have moved TOWARD the derrick,, which would be in their way.
(ii) But how?

A Little More Oomph. Wright Brothers Aeroplane Company, undated
https://www.wright-brothers.org/ ... ttle_More_Oomph.htm

Quote:

"The Wright brothers were launching the Flyer II pretty much the same way they had launched the Flyer I. They laid a wooden monorail parallel to the wind direction, whatever that happened to be. They placed a small wheeled carriage or 'truck' on the rail, then placed the Flyer on the truck. The Flyer faced into the wind

"In Kitty Hawk, there had been strong winds to help achieve flying speed. Sitting on its launch rail on 17 December 1903, the wind was already blowing at speeds in excess of 20 mph (32 kph) over the wings of the Flyer I. The aircraft had only to accelerate few miles per hour before it reached a sufficient airspeed to fly. But the winds that blew through Huffman Prairie [northeast of Dayton, Ohio, where one of he Brothers was born and both grew up] averaged only 7 to 9 mph (11 to 14 kph) throughout the summer. One most days, the Flyer II had to gain a great deal more speed than its predecessor before it could lift off successfully. The Wright brothers reasoned that a longer rail would give the aircraft more time to accelerate, and sometimes laid a monorail over 250 feet  (76 meters) long. Still, they couldn't reliably get the Flyer II up to flying speed.

"By August[, 1904], the brothers had worked out a possible solution. Wilbur informed [Octave] Chanute[, an aviation enthusiast who supplied NO money]: 'It is evident that we will have to build a starting device that will render us independent of the wind, and are now designing one.'

"The Wrights did not have access to electricity at Huffman Prairie, but they had plenty of gravity. Late in the summer of 1904, the Wilbur and Orville began to build a gravity-powered "catapult" to get them up to flying speed. A 20-foot tower (probably a salvaged derrick that had once supported a windmill) suspended up to seven donut-shaped iron weights, each weighing 200 pounds (91 kilograms), on a stout rope. This rope ran through a system of pulleys and was attached to the leading [Note 'leading'] edge of the Flyer's bottom wing by way of a tow bar. When the weights dropped, the rope pulled the Flyer II along the rail, giving the airplane just the oomph it needed to reach flying speed. From a standing start, the combined thrust of the [Flyer II's] propellers and the catapult could accelerate the Flyer to 29 miles per hour (47 kph).

Note: At the top of this Web page is an illustration. Notice a rope goes from the top of the derrick to (6) to the front (numbered (7)) of the (mono)rail and then curves back (on a pulley) toward the truck ABOVE the mail. The caption of this illustration ends with the sentence: " For more information about the Wright catapult, including an interactive 3D illustration, click HERE." Do Click, and the new Web page shows the only photo in the world of the derrick. However, the 3-D does not function.