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The specific impulse of a rocket can be defined in terms of thrust per unit mass flow of propellant. This is an equally valid (and in some ways somewhat simpler) way of defining the effectiveness of a rocket propellant. For a rocket, the specific impulse defined in this way is simply the effective exhaust velocity relative to the rocket, v e ...
The rocket is launched using liquid hydrogen and liquid oxygen cryogenic propellants. Rocket propellant is used as reaction mass ejected from a rocket engine to produce thrust. The energy required can either come from the propellants themselves, as with a chemical rocket, or from an external source, as with ion engines.
A rocket's required mass ratio as a function of effective exhaust velocity ratio. The classical rocket equation, or ideal rocket equation is a mathematical equation that describes the motion of vehicles that follow the basic principle of a rocket: a device that can apply acceleration to itself using thrust by expelling part of its mass with high velocity and can thereby move due to the ...
It is the limit case of a burn to generate a particular amount of delta-v, as the burn time tends to zero. In the physical world no truly instantaneous change in velocity is possible as this would require an "infinite force" applied during an "infinitely short time" but as a mathematical model it in most cases describes the effect of a maneuver ...
In summary, however, most formulations have a burn rate between 1–3 mm/s at STP and 6–12 mm/s at 68 atm. The burn characteristics (such as linear burn rate) are often determined prior to rocket motor firing using a strand burner test. This test allows the APCP manufacturer to characterize the burn rate as a function of pressure.
Where is the burn time in seconds, is the instantaneous thrust in newtons, is average thrust in newtons, and is the total impulse in newton seconds. Class A is from 1.26 newton-seconds (conversion factor 4.448 N per lb. force) to 2.5 N·s, and each class is then double the total impulse of the preceding class, with Class B being 2.51 to 5.00 N·s.
The grain burns at a predictable rate, given its surface area and chamber pressure. [citation needed] [17] The chamber pressure is determined by the nozzle throat diameter and grain burn rate. Allowable chamber pressure is a function of casing design. The length of burn time is determined by the grain "web thickness". [clarification needed]
Burn rate (typically expressed in mm/s or in/s) is the sample length over time at a given pressure and temperature. For solid fuel propellant, the most common method of measuring burn rate is the Crawford Type Strand Burning Rate Bomb System [3] (also known as the Crawford Burner or Strand Burner), as described in MIL-STD-286C. [4]