Could We Help Push Rockets To Orbit?

Key Concepts:

• Ground-based launch assist systems (rocket yeeting)
• Payload capacity
• Maglev catapult
• Vacuum tunnel
• Kinetic energy
• Thrust-to-weight ratio
• Delta-v (change in velocity)
• Scale and infrastructure costs
• Compromise between complexity and efficiency

1. Introduction: The Allure of Launch Assist Systems

• The video opens by highlighting the immense propellant consumption of rockets like the Saturn V (over 12,000 kg/second during first stage).
• The core question is posed: Can we improve launch efficiency by using ground-based launch assist systems to reduce the need for massive boosters?
• Tim Dodd, the Everyday Astronaut, introduces the concept of "rocket yeeting" – using systems like vacuum tunnels or maglev catapults to assist rockets.
• The video aims to explore the physics, challenges, practicality, and math behind these ideas, comparing them to traditional rockets.

2. Historical Context and SpinLaunch

• The idea of ground-based launch assist is not new, dating back to early science fiction like "La Voyage dans la Lune" (shooting humans to the moon via cannon).
• Project HARP (High Altitude Research Project) in the 1950s is mentioned: a 36-meter cannon that launched projectiles to 180km altitude.
  • Limitations: Cannot achieve orbit with a single impulse; extreme G-forces (7500 Gs) make it unsuitable for sensitive electronics or living beings.
• SpinLaunch is presented as a modern example: a centrifuge-based system that spins a rocket inside a vacuum chamber and releases it at high speed.
  • Goal: Replace the booster stage of a rocket, carrying a 200kg payload to orbit with a small liquid propellant rocket.
  • Advantages: Reusable, reliable, and sustainable due to electric motors.
  • Current Status: A 33-meter wide, one-third scale demonstrator has launched passive projectiles to almost 10km altitude.
  • Challenges: Full-scale version (100m wide) would spin at 450 rpm, inducing 10,000 Gs; precise timing of rocket release and vacuum door operation; managing heat from 7200 km/h speed.
  • Real Engineering's video on SpinLaunch is recommended for a deeper dive.

3. Hybrid Approach: Assisting Existing Rockets

• The video shifts to the idea of using launch assist systems to provide a "boost" to conventional rockets, focusing on safety and reliability.
• The preferred method is to light rocket engines on the ground before launch, allowing computer checks before releasing the rocket.
• The video uses a spreadsheet and launchcalculator.com for calculations, emphasizing that the numbers are for comparison and not precise mission planning.
• Example 1: Falcon 9 with Maglev Strongback
  • Scenario: Turning the Falcon 9's strongback (70m) into a maglev catapult with an average net acceleration of 3 Gs.
  • Results: Adds 41 m/s of velocity, increasing payload capacity by 300kg (from 17,500kg to 17,800kg) in reusable mode.
  • Energy Calculation: Requires 982 megajoules of energy (equivalent to 270 hours of Tesla Model S battery capacity).
  • Power Requirement: 450,000 kW (562 times the peak output of a Tesla Model S Plaid, or the equivalent of 375,000 average U.S. homes).
  • Challenges: Immense power requirements; protecting the strongback from rocket exhaust; potential risks of A0G engine ignition.
  • Conclusion: Only a 1.7% increase in payload capacity, making it potentially not worth the complexity.
• Example 2: Starship with Enhanced Chopsticks
  • Scenario: Using Starship's 140m launch tower and "chopstick" arms to boost the rocket with 3 Gs of net acceleration.
  • Results: Adds 54 m/s of velocity, increasing payload capacity by 5 tons (from 150 tons to 155 tons).
  • Energy Calculation: Requires 17,170 Megajoules (almost 5000 kilowatt-hours of electrical energy).
  • Power Requirement: 5.5 million kilowatts (5.5 GW) for 3.1 seconds, requiring the output of six average-sized nuclear power plants.
  • Alternative: Using a massive capacitor bank (130,000 times larger than a 50 mega Joule system shown).
  • Counterweight System: A pulley system with a counterweight would require a 175,000-ton counterweight (almost two Gerald R Ford-class aircraft carriers).
  • Conclusion: Only a 3% gain in payload capacity, with absurd energy requirements and infrastructure challenges.

4. Scaling Down: Rocket Lab's Electron

• The video explores whether launch assist systems are more beneficial for smaller rockets.
• Example: Electron with Maglev Vacuum Tunnel
  • Scenario: A 1-kilometer deep vacuum tunnel with a maglev sled accelerating the Electron at 5 Gs.
  • No engine ignition in the tunnel; the maglev provides the entire boost.
  • Results: Adds 300 m/s of velocity (more than an air launch).
  • Energy Calculation: Requires 177 kilowatt-hours of electrical energy.
  • Power Requirement: Just shy of 100,000 kW (400 superchargers).
  • Vacuum Benefit: Primarily improves efficiency by reducing friction and air resistance.
  • Challenges: Risk of pumping 100MW of electricity alongside a fueled rocket; reliance on successful engine ignition at the tunnel's end.
  • Conclusion: A 25% increase in payload capacity (from 300kg to 375kg), but the infrastructure cost may not justify the return on investment.
  • Comparison: Rocket Lab's Neutron rocket (a bigger rocket) offers a 5,000% increase in payload capacity for a similar development cost ($500 million).

5. Eliminating the Rocket: Extreme Concepts

• The video explores the idea of launch systems that don't primarily rely on rockets, such as StarTram, MagLifter, and the Lost Drum Loop.
• These concepts are often presented in renders but rarely come to fruition.
• Example: Crew Dragon Launch via Vacuum Tube Maglev
  • Scenario: Launching a Crew Dragon capsule into orbit using only a giant vacuum tube maglev system, aiming for 7500 m/s (slightly below orbital velocity).
  • G-force Limit: 5 Gs.
  • Tube Length: 573 km.
  • Tube Altitude: 100km at exit.
  • Energy Calculation: 351,000 megajoules of energy (almost 100,000 kilowatt-hours).
  • Power Requirement: 2.3 GW on average for 2.5 minutes (equivalent to a city of almost 2 million average U.S. homes).
  • Conclusion: Impractical due to the immense scale and energy requirements.

6. A Potential Application: Lunar Launch Assist

• The video suggests the Moon as a potentially suitable environment for launch assist systems due to its lower gravity (1/6th of Earth's) and lack of atmosphere.
• Lunar Orbit: Requires 1750 m/s.
• Escape Velocity: Requires another 630 m/s (total 2380 m/s to return to Earth).
• Example: Lunar Maglev Track
  • Scenario: Accelerating payloads from the lunar surface back to Earth.
  • Acceleration: 5 Gs.
  • Track Length: 58 km.
  • Energy Calculation: 35,000 megajoules of energy for a Dragon capsule.
  • Power Requirement: 668,000 kW on average.
  • Conclusion: Still requires significant infrastructure and energy, but may be feasible for transporting resources like helium-3 or lunar regolith at higher Gs.

7. Synthesis/Conclusion

• The biggest takeaway is an appreciation for the immense energy produced by rockets.
• A major problem with launch assist systems is the commitment to a specific infrastructure, which can become a bottleneck if vehicle designs change.
• The "KISS" (Keep It Simple, Stupid) principle often prevails: building a slightly bigger rocket is often easier than complex launch assist systems.
• However, if spaceflight becomes extremely common (multiple launches per hour), large ground-based infrastructure might become more feasible.
• The video concludes by asking viewers whether they would build a traditional rocket or try to maximize performance with launch assist systems.