1. What is Specific Impulse?

Specific Impulse (I_sp) is a measure of how efficiently a rocket engine uses propellant. It represents the impulse (change in momentum) per unit of propellant and is essentially the "miles per gallon" rating for rocket engines.

2. How Does the Calculator Work?

The calculator uses the specific impulse equation:

Where:

• \( I_{sp} \) — Specific impulse (seconds)
• \( F \) — Thrust force (Newtons)
• \( m \) — Mass flow rate of propellant (kg/s)
• \( g \) — Standard gravity (9.81 m/s² on Earth)

Explanation: The equation shows that specific impulse is directly proportional to thrust and inversely proportional to both mass flow rate and gravitational acceleration.

3. Importance of Specific Impulse

Details: Specific impulse is crucial in rocket design as it determines the propellant efficiency. Higher I_sp means less propellant is needed for a given amount of thrust, allowing for smaller fuel tanks or longer burns.

4. Using the Calculator

Tips: Enter thrust in Newtons, mass flow rate in kg/s, and gravity in m/s² (9.81 for Earth). All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What are typical specific impulse values?
A: Chemical rockets typically range from 200-450s. Ion thrusters can reach 3000-5000s but with much lower thrust.

Q2: Why is specific impulse measured in seconds?
A: The units work out to seconds dimensionally, and it represents how long 1kg of propellant can produce 1kg of thrust (at Earth gravity).

Q3: How does specific impulse affect rocket performance?
A: Higher I_sp means less propellant needed for the same delta-v, allowing for more payload or longer missions.

Q4: Does specific impulse change with altitude?
A: The engine's I_sp is constant, but effective performance may vary with external pressure.

Q5: What's the highest specific impulse possible?
A: Photon rockets (using light) theoretically have infinite I_sp but negligible thrust.