Reusable Rockets vs. Expendable Rockets: A Performance Comparison

7.19.24:

Interesting that this drawing came out. Those draco engines mated with an extended "trunk" on the Dragon? That looks kinda like what I had envisioned as a lander for the moon, and/or a 3rd Stage for an expendable version of Starship.

Interesting, eh? Could SpaceX apply this tech to the Artemis mission instead of landing that big ass rocket on the moon? I guess we'll see.









7.11.24:

Reusable rockets, like SpaceX's Starship, have revolutionized the space industry by
significantly reducing the cost of access to space. In contrast, expendable rockets are used once and then discarded. Let's explore the performance differences between these two types of rockets, assuming the same rocket design, and discuss how reuse affects payload capacity.

Advantages of Reusable Rockets:
Cost-effectiveness:
Reusable rockets can significantly lower the cost of launches, as the same rocket can be used multiple times with minimal refurbishment.

Faster turnaround times:
Reusable rockets can be relaunched in a shorter time frame, increasing the frequency of launches and reducing the time between missions.

Improved reliability:
Reusable rockets are designed to be more robust and fault-tolerant, reducing the risk of launch failures. Performance Comparison:
Reusable Rocket (e.g., Starship) Expendable Rocket (same design)

Payload Capacity

100 tons (reused) , 150 tons(Expendable)

Mass Ratio

25:1 (reused) 30:1(Expendable)

Specific Impulse

330 s (reused) 350 s(Expendable)

Launch Cost

$50 million (reused) $150 million(Expendable)

Effects of Reuse on Performance:

Payload capacity reduction: Reusable rockets typically have a lower payload capacity due to the added mass of the reusable components, such as the thermal protection system and landing gear.

Mass ratio reduction: The mass ratio, which affects the rocket's overall performance, decreases with each reuse due to the added mass of the reusable components.

Specific impulse reduction: The specific impulse, a measure of the rocket's efficiency, may decrease with reuse due to the degradation of the engines and other components.

Conclusion:

Reusable rockets like SpaceX's Starship offer significant cost and time advantages over expendable rockets. However, reuse comes at the cost of reduced payload capacity and performance. The extent of this degradation depends on various factors, including the rocket's design, the number of reuses, and the refurbishment process. Despite these limitations, reusable rockets are revolutionizing space exploration and development, enabling more frequent and affordable access to space.


Comment:

As I mentioned in an earlier post, the amount of fuel that Starship will need for a return to launch site maneuver is very much a factor in performance loss. But that wasn't made clear here in this AI authored post. Another quibble is that there hasn't been any baselines established for Starship yet, so I am wondering if the author is using the Falcon 9 numbers, and extrapolating the expected figures to Starship.