Could we help throw rockets to orbit? #rockets #spacex #starship

Key Concepts:

• Stage Zero Launch Tower (SpaceX)
• Starship (SpaceX)
• Chopstick Arms
• Catapult Launch Assist
• G-Force (G)
• Payload Capacity
• Megajoules (MJ)
• Counterweight System

Analysis of Catapult Launch Assist for Starship

1. Potential Velocity Gain and Payload Increase:

• The core idea explored is whether the SpaceX launch tower's "chopstick arms" could be used to provide an initial boost to Starship, similar to a catapult.
• If the entire 140-meter tower could accelerate Starship at a net 3G (three times the force of gravity), it would result in an additional 54 meters per second of velocity.
• Assuming Starship's baseline payload capacity is 150 tons to orbit, a 54 m/s boost would increase the payload by approximately 3%, resulting in a 155-ton payload.

2. Energy Requirements for a 3G Boost:

• Starship has a mass of approximately 5,000 tons.
• To lift Starship at a net 3G while its engines are running would require over 17,000 megajoules (MJ) of energy.
• This energy demand is equivalent to the electrical power output of almost six average nuclear power plants operating for three seconds.

3. Mechanical Catapult with Counterweight:

• An alternative approach considered is a mechanical catapult system using a counterweight.
• To provide a 2.5G boost to Starship, the counterweight would need to have a mass of 175 million kg.
• This mass is comparable to almost two Gerald R. Ford-class aircraft carriers.
• Even if the counterweight were made of steel, a 22,000 cubic meter block would be required, making it extremely large and expensive.

4. Structural and Engineering Challenges:

• The analysis highlights the significant structural and engineering challenges associated with a catapult launch system.
• The tower, cables, chopstick arms, and overall structure would need to be incredibly strong, heavy, and expensive to withstand the forces involved.
• Starship itself would need to be reinforced to handle the acceleration forces imposed by the catapult.

5. Cost-Benefit Analysis and Alternatives:

• The analysis concludes that the extra complication, cost, and risk associated with a catapult launch system are not justified by the relatively small 3% increase in payload capacity.
• It suggests that upgrading the engines or increasing the size of the rocket would be more practical and cost-effective ways to achieve a similar performance gain.
• The video implies that the marginal gains are not worth the exponential increase in complexity and cost.

6. Why Catapult Launches Are Not Common:

• The video states that there's a reason why catapult launches are not commonly used for orbital rockets.
• The analysis suggests that the benefits are typically outweighed by the costs and complexities.

7. Notable Quotes:

• "Upgrading the engines or just increasing the size of the rocket is usually a much easier way to get a 3% gain." This statement encapsulates the core argument against the catapult launch concept.

Synthesis/Conclusion:

The video explores the feasibility of using SpaceX's launch tower to provide a catapult-like boost to Starship. While theoretically possible, the analysis reveals that the energy requirements, structural challenges, and costs associated with such a system are substantial. The relatively small 3% increase in payload capacity does not justify the complexity and risk involved, making alternative approaches like engine upgrades or rocket resizing more practical and cost-effective solutions. The video effectively demonstrates why catapult launches are not a common practice in the space industry.