query: Are there any new types of helicopters?
passage: Helicopter
NASA is developing the Mars Helicopter Scout, a 1.8kg (4.0lb) helicopter to be launched to survey Mars (along with a rover) in 2020. Given that the Martian atmosphere is 100 times thinner than that of Earth's, its two blades will spin at close to 3,000 revolutions a minute, approximately 10 times faster than that of a terrestrial helicopter.[63]
passage: Amphibious helicopter
Helicopters can be designed to withstand limited contact with the surface of a body of water. The 1958 Vertol HUP-2 was an amphibious development of the twin-rotor Piasecki H-25 which strengthened its hull and replaced lower nose windows with tough aluminum. The HUP-2 was provided with a pair of stabilizing outrigger floats positioned amidships. The HUP-2 was able to taxi forward or backward on water, regardless of wind direction.
The CH-46 Sea Knight and its Canadian variant, the CH-113 Labrador, can land on water and rest for up to two hours in calm water. The rear sponsons hold two of the three landing gear units as well as self-sealing fuel tanks. The helicopter began service with the United States Marine Corps in 1962, and with the Canadian military in 1963, and is used to carry cargo and combat troops.
The Boeing CH-47 Chinook was made sufficiently watertight to allow it to land on water for a short time in carrying out covert operations and special military missions. Buoyancy was increased with sealed compartments inside sponsons which extended most of the way along each side of the fuselage. For extended water usage, Boeing offered a kit to enhance its water resistance. The Sikorsky CH-53 Sea Stallion, first introduced in 1966, is also capable of limited water landing.