Speed Booster

The Speed Booster (スピードブースター) is a power-up that first appears in Super Metroid in Norfair right after Samus defeats Kraid and obtains the Varia Suit. It also appears in Metroid Fusion when Samus defeats Serris in Sector 4 and in Metroid: Zero Mission when Samus defeats Kraid in his lair. This upgrade also appears in Metroid: Other M.

Description
According to the Metroid Fusion and Metroid: Zero Mission Instruction Manuals, the Speed Booster allows Samus to run at "supersonic speeds." This indicates that she can move from her normal speed to Mach 1.2 and possibly up to Mach 4.9.

The Speed Booster, as the name suggests, will greatly increase Samus's speed whilst she runs. She also becomes invincible, as noted in the Super Metroid instruction manual, although in-game contradicts this. In Super Metroid, the Speed Booster would only activate if holding the dash button, but in later games it activates automatically after a certain distance, most likely due to the lack of the X and Y or similar buttons on the Game Boy Advance and Wii.

The Speed Booster is notable for being used in intricate, difficult puzzles for expansions, though it is actually required to advance further in the game, on occasion. Also, the Speed Booster has been shown to be quite a powerful weapon, being able to plow through most enemies, rocks, ice walls, chunks of ice that take a similar form of stalagmites that are located in the Cryosphere, and Boost Blocks, which cannot be destroyed with any other weapon, no matter how powerful.

Additionally, the Speed Booster has two notable extra forms: the Shinespark and a fast, far-reaching Spin Jump. The Shinespark allows Samus to store a Speed Booster charge for a short period of time and then to use that charge to move continuously in one direction (left, diagonal left, up, diagonal right, right). The Spin Jump, quite obviously, is when Samus spin jumps while Speed Boosting; this is most effective when used with the Space Jump, so Samus can jump continuously.

Uses
The Speed Booster is very useful in the following instances:
 * Melting Boost Blocks.
 * Breaking through hardy materials like rock, ice, and metal.
 * Running through enemies.
 * Traversing distances in a short amount of time.
 * Traversing steep ascents.
 * Setting up a shinespark.

Super Metroid manual
"These boots allow Samus to run at a super high speed and make her invincible as she runs through enemies. Blocks with the Speed Booster icon melt away when Samus runs into or over them at super speed."

Metroid Fusion manual
"Dash at supersonic speeds and crash through certain barriers and enemies. Press and hold the Control Pad in the direction you want to dash."

Metroid: Zero Mission manual
"With this power-up, Samus is able to dash at supersonic speeds and crash through certain barriers and enemies. Press and hold + in the direction you want to dash."

Zero Mission Samus Screen data
"Run until speed boost begins to break certain blocks and damage enemies."

Metroid: Other M on-screen tutorial
SPEED BOOSTER '' Run for a while in one direction. You can cause damage by running into things and climb steep ascents .''

Metroid: Other M manual
"Press and hold +* and move in a single direction for a certain period of time to start to run fast. You can also cause damage to enemies that you run into."

Metroid: Other M Samus Screen data
"Effects: Allows Samus to run extremely fast and damage things she impacts. Controls: Press + in one direction and run for a while."

* Plus sign represented by Wii Remote D-Pad.

Trivia

 * In Metroid Fusion and Metroid: Zero Mission, if Samus stops running in mid boost, the player can hear the slight sound of Samus' boots scraping against the ground to slow down.
 * Samus is able to use the Blue Suit glitch when fighting Draygon.
 * The Speed Booster's Shinespark is a reference to 1970's mech anime Getter Robo G in which it was the titular robot's most powerful attack, however like its Super Metroid counterpart usage quickly drained it of energy.
 * An interview with Retro Studios revealed that the Speed Booster was once considered for inclusion in Metroid Prime, but did not appear due to difficulties implementing it. Unused scan images show Samus performing what appears to be a Shinespark.
 * Metroid: Other M is the first and currently only game to have a 3D appearance of the Speed Booster.
 * Other M is also the first game to reveal how the Speed Booster works. The thrusters on the back of her suit fire and propel her at great speeds, though she must continue running as the thrusters do not provide lift required for her to fly.
 * The start-up time for the Speed Booster differs in each of the Metroid games that features this upgrade, thus making it a game-mechanic. In Super Metroid it takes about 1 second. In Metroid Fusion and Metroid: Zero Mission it takes about 2 seconds. In Metroid: Other M it takes about 5 seconds.
 * Based on Samus' mass, as well as the speed she travels with the Speed Booster, she would produce 37,044 newtons of force, or 7,623,655.2 joules (7.624 × 10⁶).