Could Vulcan Carry the Orion Capsule Instead of the SLS?

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The Orion spacecraft, a critical component of NASA’s Artemis program, is designed for deep-space crewed missions, including returning astronauts to the Moon and eventually reaching Mars. The Space Launch System (SLS) is the designated rocket for carrying Orion, but its high costs and development challenges have led to considerations of alternative vehicles. One potential candidate is United Launch Alliance’s (ULA) Vulcan Centaur, a heavy-lift rocket currently in advanced stages of development. This article examines the feasibility of using Vulcan to carry the Orion spacecraft, considering technical, logistical, and programmatic aspects.

Vulcan Centaur Overview

Vulcan Centaur is the successor to ULA’s Atlas V and Delta IV rockets, designed to meet diverse mission needs while lowering launch costs. It incorporates advanced technologies, a modular architecture, and partial reusability through the recovery of its engines.

Key Features of Vulcan Centaur

• First Stage: Powered by two BE-4 engines fueled by liquefied natural gas (LNG) and liquid oxygen (LOX), producing approximately 4.5 million pounds of thrust.
• Second Stage (Centaur V): An upgraded version of the Centaur upper stage, powered by two RL10 engines optimized for efficiency in space.
• Payload Capacity: Estimated at 27.2 metric tons to low Earth orbit (LEO) and approximately 14 metric tons to trans-lunar injection (TLI) in its standard configuration.
• Solid Rocket Boosters (SRBs): Up to six solid rocket boosters can be added for increased payload capacity.
• Reusability: Plans include recovering the BE-4 engines through the SMART (Sensible Modular Autonomous Return Technology) system.

Vulcan Centaur is designed to cater to a range of commercial, scientific, and national security missions, making it a versatile launch vehicle.

Orion Spacecraft and Its Requirements

The Orion spacecraft is composed of the following components:

1. Crew Module: Accommodates up to four astronauts and provides life support during missions.
2. Service Module: Developed by the European Space Agency (ESA), it provides power, propulsion, and thermal control.
3. Launch Abort System (LAS): Designed for crew safety during launch emergencies.

The total mass of Orion, including its LAS and service module, is approximately 26 tons. To support missions to the Moon, the launch vehicle must deliver this payload to a trans-lunar injection trajectory. This requires a rocket with sufficient thrust, precise orbital insertion capabilities, and compatibility with Orion’s unique design.

Comparing Vulcan and SLS Capabilities

Payload Capacity

The SLS Block 1 configuration can deliver up to 95 metric tons to LEO and 27 metric tons to TLI, allowing it to launch Orion and its associated payloads directly to the Moon. Vulcan Centaur, on the other hand, has a maximum payload capacity of approximately 14 metric tons to TLI in its standard configuration, which is insufficient to directly launch Orion.

To accommodate Orion, Vulcan would require modifications or additional infrastructure, such as an upper stage capable of boosting Orion to TLI. ULA’s proposed Advanced Cryogenic Evolved Stage (ACES) could address this gap, providing additional thrust and capabilities for deep-space missions.

Launch Abort System Integration

Orion’s Launch Abort System is designed for the SLS and requires a wide payload fairing to house its components. Vulcan’s payload fairing is narrower, meaning significant modifications would be necessary to integrate Orion. These changes would include reinforcing the fairing structure to support Orion’s weight and adapting the aerodynamics to ensure stability during ascent.

Reusability and Cost Efficiency

One of Vulcan’s advantages is its focus on cost reduction through modularity and partial reusability. By recovering its BE-4 engines, ULA aims to lower launch costs over time. While the SLS is fully expendable and costs an estimated $2 billion per launch, Vulcan’s modular design offers potential for more economical missions, provided it can meet Orion’s technical requirements.

Technical Challenges and Modifications

Payload Fairing

Vulcan’s existing payload fairing is narrower and shorter than the SLS core stage, presenting a challenge for accommodating Orion and its Launch Abort System. Modifications to the fairing would require extensive engineering and testing to ensure compatibility and safety. Such changes could also affect Vulcan’s aerodynamics and performance.

Trans-Lunar Injection

To meet the trans-lunar injection requirements for Orion, Vulcan would likely need an upgraded upper stage. The Centaur V stage currently lacks the capability to deliver Orion’s full mass to the Moon. However, ULA has proposed the ACES, which could provide the necessary performance. This stage would feature advanced cryogenic propulsion, in-space refueling, and extended mission durations, potentially enabling Vulcan to carry Orion.

Infrastructure and Launch Pad Modifications

Vulcan is set to launch from Space Launch Complex-41 (SLC-41) at Cape Canaveral. While this infrastructure supports Vulcan’s standard operations, modifications would be needed to accommodate Orion’s integration and fueling requirements. These changes could include upgrades to the payload processing facilities and ground support systems.

Mission Profile

Unlike the SLS, which can deliver Orion directly to a trans-lunar trajectory, Vulcan would require a more complex mission profile. This could involve launching Orion into low Earth orbit (LEO) and using an additional propulsion stage or in-orbit refueling to reach the Moon. While technically feasible, this approach introduces additional complexity and potential risks.

Programmatic Considerations

Certification for Crewed Missions

For Vulcan to carry Orion, it must meet NASA’s rigorous certification standards for crewed missions. This process would involve:

• Compatibility testing with Orion’s systems.
• Demonstrating reliability and performance through multiple test flights.
• Validating safety systems, including the Launch Abort System, in conjunction with Vulcan.

Given Vulcan’s current development stage, achieving certification for crewed missions would require significant time and investment.

Artemis Program Timeline

NASA’s Artemis program has set ambitious timelines, including landing astronauts on the Moon within the next few years. Vulcan’s first launch is expected soon, but adapting it for Orion would necessitate additional development, testing, and certification. These requirements could delay Artemis milestones, reducing Vulcan’s viability as a near-term replacement for the SLS.

Policy and Collaboration

Transitioning from SLS to Vulcan as Orion’s launch vehicle would require coordination between NASA and ULA, as well as Congressional approval. Funding reallocations and policy decisions would play a critical role in determining the feasibility of such a transition.

Potential Benefits of Using Vulcan

1. Cost Savings: Vulcan’s modular design and partial reusability could lower launch costs compared to the fully expendable SLS.
2. Flexibility: Vulcan’s adaptability for different payloads and missions makes it a versatile option for NASA’s exploration goals.
3. Commercial Synergy: Collaborating with ULA aligns with NASA’s strategy of leveraging commercial partnerships to advance space exploration.

Summary

While Vulcan Centaur presents an intriguing alternative to the SLS for carrying the Orion spacecraft, significant challenges remain. Its current payload capacity to TLI is insufficient for directly launching Orion, necessitating upgrades such as the ACES upper stage or in-orbit refueling. Additional modifications to the payload fairing, ground infrastructure, and mission profile would also be required.

Despite these challenges, Vulcan’s focus on cost efficiency and flexibility makes it a viable option for future exploration efforts. As NASA continues to explore commercial partnerships, Vulcan could play a complementary role in enabling Artemis and other deep-space missions. However, in the near term, the SLS remains the most capable and readily available option for launching Orion to the Moon.