Rocket Launches Explained
The traditional method of launching orbital rockets into space involves a vertical liftoff. Although it may seem counterintuitive at first, there is a logical reason behind this approach.
Minimizing Atmospheric Resistance
Watching a rocket launch, it’s common to feel impatient as it slowly gains altitude and speed. In comparison to conventional aircraft, this method appears impractical and inefficient.
The primary objective of a vertically launched rocket is to rapidly traverse the densest part of the atmosphere, where air resistance is most significant, and perform a gravitational turn to orient the vehicle more horizontally. This allows the rocket to continue accelerating until it reaches orbital or escape velocity.
Aircraft, on the other hand, operate within the atmosphere, relying on air to stay aloft. Consequently, there are fundamental structural and operational differences between rockets and aircraft that determine their takeoff and flight patterns.
Overcoming the Earth’s Atmosphere
To reach and maintain orbit, a spacecraft must achieve a speed of approximately 28,000 km/h (17,500 mph), equivalent to 8 kilometers per second. However, near the Earth’s surface, the dense air would require an impractical amount of energy and fuel to generate such high speeds.
Therefore, launching a rocket vertically enables it to clear the thickest part of the atmosphere as quickly as possible, before reorienting itself to a more horizontal position to achieve the required speed.
The Role of Gimbal Thrusters
A gravitational spin is a maneuvering procedure where a rocket uses its gimbal thrusters to tilt the vehicle away from its vertical position, allowing the Earth’s gravity to push the rocket toward a more horizontal orientation while gaining altitude and accelerating to orbital speed.
After tilting, the rocket continues its ascent in a parabolic trajectory, accelerating to reach orbital speed. It must also achieve a minimum altitude of 150 to 200 kilometers (93-124 miles) to reach low Earth orbit.
Atmospheric Considerations
Rockets and aircraft spend varying amounts of time in the Earth’s atmosphere. While airplanes spend their entire time in the atmosphere, rockets only spend a brief period before entering the vacuum of space.
Airplanes need to travel horizontally at sufficient speeds to generate lift and stay airborne, supplying oxygen to their engines. In contrast, rockets expend their energy to create thrust, escaping the dense atmospheric air near the surface and reaching orbital speed.