Why Doesn't NASA Use a Spacecraft Rather Than a Shuttle Strapped to a Large Rocket?
The question of why NASA doesn’t use a spacecraft rather than a shuttle strapped to a large rocket is a common discussion point among space enthusiasts. The space shuttle was a fully functional spacecraft, as were Soviet Soyuz, SpaceX Crew Dragon, and Boeing Starliner. However, the notion of flying a spacecraft directly into orbit without the need for a powerful rocket is more complex than it might seem.
The Need for Rockets
Spacecraft like the space shuttle are indeed capable of reaching space, but they operate under the constraints of gravity and atmospheric conditions. Simply flying an airplane higher and higher is not sufficient to enter space. The reason is that the atmosphere becomes too thin before reaching the Karman Line, approximately 100 kilometers above the Earth’s surface, where space is generally considered to begin. Additionally, to achieve orbit, a spacecraft must travel at an incredible speed of around 7 kilometers per second, roughly 7,000 meters per second. Compare this to the world speed record holder, the SR-71 Blackbird, which can only reach 3,500 kilometers per hour, or about 1,000 meters per second. Therefore, a spacecraft must be capable of reaching this extreme speed.
The Complexity of SSTOs
The idea of flying a spacecraft directly to orbit without discarding a large rocket is known as Single-Stage-To-Orbit (SSTO). This concept is highly intriguing, but also incredibly complex and challenging. An SSTO vehicle must be capable of carrying its own fuel and having enough leftover fuel to perform the final stage of the mission, which is often referred to as orbital insertion. Designing an SSTO vehicle would require a very lightweight and efficient spacecraft, which would make it almost impossible to achieve the necessary speed and altitude without significant technological advancements.
Cost and Reusability
The space shuttle, despite its complexity and weight, was a reusable spacecraft designed with the ability to transport both people and cargo into orbit. While it didn't appear small by any means, its design was a testament to the efforts to optimize both performance and reusability. The current thinking in the space industry is that discarding a large rocket after a single use is more cost-effective than throwing the entire spacecraft away after each voyage. This approach allows for the recovery and reuse of expensive components like engines, reducing overall mission costs.
Advancements in Commercial Crew Vehicles
SpaceX has made significant strides in this area with the successful launch of Crew Dragon and the upcoming flights of Starliner. These spacecraft are designed to be capsule-like, taking a simpler, more efficient approach in which the crew module can safely return to Earth. This design tradeoff emphasizes safety and reduces the overall load. NASA's Orion spacecraft, while intended for longer missions to the Moon and beyond, is not as efficient for short, frequent trips to Low Earth Orbit (LEO).
The Future of Space Exploration
The current landscape of space exploration is rapidly changing, with multiple companies and organizations working on innovative solutions. SpaceX has shown that reusable rockets, like the Falcon family, can be safely landed and reused, significantly reducing the cost of launches. This breakthrough could pave the way for future SSTO designs. However, the technology and infrastructure required to build such spacecraft are still in the realm of future possibilities, given current funding and technological constraints.
As we continue to push the boundaries of space exploration, the ideas of SSTO and the future of space travel remain captivating and worth pursuing. The efforts of organizations like NASA, SpaceX, and other commercial space companies are bringing us closer to a future where humans can travel to space more frequently and cost-effectively.
Conclusion
The question of why NASA doesn’t use a spacecraft rather than a shuttle strapped to a large rocket is a testament to the evolving nature of space technology. While the answers lie in the complexities of orbital mechanics, cost, and technological limitations, the ongoing advancements in the industry give us hope for a future where space exploration becomes more accessible and efficient.