Introduction:

Tim Dodd, the Everyday Astronaut, guides viewers on a tour of SpaceX’s Starbase factory with Elon Musk. This is part two of the tour, and they discuss the Raptor engines and their developments.

Transparency and Technology:

Elon Musk mentions that the tour might reveal more than ITAR and communications departments might want but states it isn’t more than what people can capture with telephoto lenses. He is open to others trying to copy the Raptor design and indicates that Raptor 2 will be a significant improvement over the current design.

Raptor Engine Evolution:

Elon discusses the Raptor engine’s evolution, particularly mentioning that Raptor 2 will be visibly cleaner with less complexity in plumbing and wiring. He describes the original Raptor engine as looking like a “Christmas tree” due to the excess components.

Technical Details:

The tour goes into the technicalities of Raptor engines, touching on the ‘regen channel,’ steel tube walls, and throat diverging sections. Elon mentions they are aiming for a higher expansion ratio and an “aspirational” ISP (Specific Impulse) of 380 for the new Raptor engine.

Standardization:

Elon reveals plans to standardize the pumps and thrust chamber assemblies across all Raptor engines. The primary difference would be the presence or absence of thrust vector control actuators, simplifying the production process.

Comparison with Soviet Engines:

Towards the end, the discussion veers into comparing SpaceX’s engines with Soviet-era engines, mentioning their simplicity but lack of advanced electronics. Elon agrees that older engines lacked sophisticated electronics but doesn’t see that as an advantage.

Future Outlook:

Though Elon doesn’t reveal all the “secrets,” he clearly states that Raptor 2 will be more efficient and streamlined than its predecessor. The aim is not just to improve the engine but to make it more manufacturable and reliable.

The tour serves as an insightful look into the rapidly evolving technologies at SpaceX, especially the advancements in their Raptor engines.

Failure as an Option:

Elon Musk discusses the culture of embracing failure at SpaceX, especially when it comes to Starship development. He notes that failure is a crucial part of the iterative process for achieving technological advancements. With the SN8 Starship test, for example, the goal wasn’t to complete a mission but to gather valuable data.

Different Risk Profiles for Different Projects:

Musk compares the risk optimization strategies for different SpaceX projects. Dragon, a spacecraft designed for carrying humans, cannot afford any failures and is therefore developed conservatively. Falcon rockets are less conservative; a failure in booster landing is not disastrous. Starship, however, is on the polar opposite of Dragon, designed for rapid iteration to create a fully and rapidly reusable orbital rocket.

The Pitfalls of Space Shuttle’s Risk Aversion:

Musk critiques the Space Shuttle program for its lack of iteration due to the high risk associated with human lives on board. He argues that the design for the Space Shuttle froze because changes posed risks, which led to known problems not being addressed. The Space Shuttle program suffered from a risk-reward asymmetry, where the risks of changes overshadowed the benefits, stymieing innovation.

Considerations for Launch Escape:

Musk argues that traditional launch escape systems are limited in their coverage and introduce additional failure modes. Unlike these systems, SpaceX’s Dragon has escape capabilities all the way to orbit. However, for missions beyond Earth, like the Moon or Mars, escape systems are impractical. The Starship, therefore, must be reliable without an escape system, and this can only be achieved through extensive testing and iteration.

Final Thoughts:

Musk emphasizes that the strategy for Starship is to fly it extensively without people on board to understand and mitigate all failure modes. This strategy contrasts with that of the Space Shuttle program, which was constrained by its inability to risk failure due to human presence. The key to SpaceX’s innovative approach lies in understanding and embracing different risk profiles for different projects.

Start Now Philosophy:

Elon Musk advocates for a “start now” philosophy. When discussing starting a YouTube channel or any venture, he says that one should just start because you will not know the challenges or how to make it better until you make the first move.

Thermal Protection:

Musk talks extensively about the thermal protection system of a spacecraft, specifically mentioning how the tiles are a crucial component. The ceramic tiles undergo significant temperature changes, from room temperature to cryogenic levels and then above room temperature. He outlines the complexities involved in ensuring that the tiles can handle such changes without cracking, which would be catastrophic during re-entry.

Monitoring and Feedback:

Musk says they use temperature sensors and internal cameras to monitor the performance of the thermal protection system. This allows them to identify areas that may be glowing white-hot, which is an indication of failure. The monitoring ensures they can spot a crack in the armor, so to speak.

Orbital Test Details:

Elon Musk addresses the first orbital test, saying that the spacecraft will achieve orbital velocity but won’t circularize its perigee. He elaborates that the spacecraft will go around three-quarters of the Earth, and due to not raising the perigee, atmospheric drag will pull it back for re-entry.

Recovery and Iteration:

When asked about the recovery of the spacecraft, Musk states that learning from the first orbital test is key, even if it ends in failure. The data collected will help in identifying the areas of improvement, and potentially raising the perigee in future tests would be remarkably easy.

This segment from the longer presentation encapsulates Musk’s approach to iterative development, his thoughts on the importance of thermal protection, and the plans for initial orbital tests.

Objective of First Orbital Launch:

Elon Musk emphasizes that the primary goal of SpaceX’s first orbital launch is to make it to orbit without any explosions. Even if the booster performs well but something goes wrong with the ship, it would be considered progress.

Significance of Stage Zero:

Musk introduces the term “Stage Zero” to describe the launch mount, flame diverter, tower, propellant farm, and associated systems. According to him, constructing Stage Zero is more challenging than making a booster or a ship. It’s crucial that Stage Zero doesn’t explode, as it is harder to replace.

Best-Case Outcome for First Flight:

The optimal result for the first flight would be for the booster to perform its job and splash down in the Gulf, 20 miles away. The ship or upper stage would come in near a military base off the coast of Hawaii.

Landing and Booster Positioning:

The plan involves the booster venting gas to orient itself for re-entry, followed by a boost-back burn to reduce the distance it would otherwise travel. The aim is to position the booster precisely enough to confirm that landing mechanisms, humorously referred to as “Mechazilla,” could have successfully grabbed it.

Transparency and Rapid Iteration:

Musk acknowledges the transparency of this rocket development process, comparing it to “washing laundry in public.” Despite the visibility, SpaceX intentionally iterates designs rapidly. Each ship and booster has different iterations, and some are even expected to blow up as part of the process to push the envelope.

Fully and Rapidly Reusable Rocket:

The ultimate goal is a fully and rapidly reusable rocket system. Musk notes that to achieve this, they must operate close to the edge on margins. Adding extra mass for safety could recursively increase the need for more propellants, making the rocket less efficient.

The summary reveals SpaceX’s approach of risk-taking, rapid iteration, and public transparency in its quest to revolutionize space travel.

Mass and Propellant:

Elon Musk discusses the intricate relationship between a rocket’s mass and the amount of propellant required for various phases like de-orbiting and landing. For each ton of mass, the rocket structure has to carry additional load, including extra propellant and heat shields, making the effective weight almost two times the original. This is described as having a “recursive value.”

Dry Mass Ambiguity:

Musk admits uncertainty about the exact dry mass of the S20 rocket, mentioning that many parts have yet to be weighed. He hopes that the dry mass won’t exceed 100 tons. He further clarifies that “dry mass” can have different meanings, including or excluding the air inside the rocket, propellant residuals, and ullage gas at several atmospheres.

Engine Efficiency:

Musk talks about the thrust-to-weight ratio of rocket engines and the efficiency of different engine architectures. He notes that while their GG (Gas-Generator) cycle engine is highly optimized, it is inherently limited by the architecture. Musk compares the engine’s efficiency to gymnastics, where both the difficulty of the routine and the execution matter. For future versions, he anticipates reaching an “A-plus” in engine efficiency.

Future Versions:

When asked about the rating he would give to the upcoming version 2 of their rocket, Musk suggests a “B-plus,” noting that with future iterations—version 3, 4, 5—the rocket will likely achieve an “A-plus” rating in terms of efficiency and capabilities.

Nose Cone Evolution:

Elon Musk introduces a new and improved nose cone design. The previous design was assembled using stamped sections, made of three rows of metal. The new nose cone is made of two rows of stretch foam, resulting in a smoother surface. This is done by stretching a large sheet of steel over a mandrel, a technique not achievable using traditional stamping presses.

Minimizing Complexity:

Musk explains that work on the rocket’s fairing door has been halted. The primary focus now is on achieving orbital flight and safe return of the ship. He views additional features like doors as unnecessary complexity at this stage. The objective is to eliminate all elements that don’t directly contribute to reaching orbit.

Retirement of Early Rockets:

Elon Musk discusses the lifecycle of rockets, stating that the early versions returned from orbit probably won’t be flown again, much like the early versions of Falcon 9’s Block 5. He mentions that these early versions are difficult to prepare for subsequent flights and are thus more likely to be retired. Therefore, adding additional features like a door is considered impractical since these rockets are not planned for future satellite missions.

Progressive Improvement:

Musk stresses that the early versions of rockets serve as stepping stones towards more advanced and efficient designs. He suggests that the first rockets are likely to become “lawn ornaments,” highlighting that their value lies in the lessons learned for developing subsequent, more effective models.

Orbital Refueling:

Elon Musk emphasizes that orbital refueling is not an immediate concern for their rockets. Refueling in orbit becomes necessary for missions to the Moon and Mars, but not for delivering satellites to Earth orbit. The focus is initially on reaching orbit and returning successfully.

Propellant Drain Lines:

The conversation moves towards design details like propellant-filled drain lines, which have been switched to the V-side instead of running through the booster. Musk mentions that it’s better to move masts to the ground side where possible, explaining that this approach influenced the removal of legs from the rocket booster.

Tower Catcher:

A concept named the “tower catcher” is briefly mentioned. Elon Musk acknowledges that the idea may sound unusual but suggests that it could work, particularly given the difficulties of handling large rocket components in windy conditions.

Stacking and Launch Mechanisms:

Musk elaborates on the complexity of stacking the rocket and preparing it for launch. While the plan is to eventually use “Mechazol arms” for this task, the initial stacking will be done with a crane due to the arms still being in the assembly stage. The team aims to proceed with launches without waiting for the tower to be completed.

Changing Plans:

Musk warns that everything is a work in progress and that plans could change from week to week. The reason for such changes could be anything from miscommunication to better ideas emerging.

Launch Pad Considerations:

Finally, Musk emphasizes that they must use a “super beefy” orbital launch pad for the mission as the suborbital pad is not designed to handle the full weight and height of the rocket stack. The aim is to move ahead with mounting the booster as soon as possible.

Stacking Logistics:

Elon Musk discusses how the team doesn’t want to wait for the completion of the launch tower for stacking the spacecraft. He says that if the tower isn’t ready in time, they’ll use a crane for stacking. The QD (Quick Disconnect) arm is crucial for stabilization and propellant transfer; without it, propellant can’t be loaded onto the ship.

Development Concerns:

Musk shares that there are many moving pieces in the project and acknowledges a long list of items that need solving. He is particularly concerned about time risks, stating that time is the one thing you cannot replace.

Optimistic Scheduling:

He admits to being “pathologically optimistic” about schedules, but also emphasizes that his optimism drives him to undertake ambitious projects.

Aesthetic Observations:

There is a brief discussion about the appearance of the spacecraft. Descriptions like “dragon scales” are used, indicating an appealing and “tidy” aesthetic, despite a few broken tiles.

Flap Cooling and Design Error:

Elon Musk discusses the need for cooling the joints of the flaps on a spacecraft, contradicting the common perception that wind could naturally cool them. Musk mentions a design error concerning the non-moving portion of the forward flaps. These flaps serve two primary purposes: rebalancing the ship’s center of mass and maintaining the appropriate angle during hypersonic flight.

Heat Management Strategies:

Musk explains that heat management varies depending on the type of heat shield. For Dragon’s ablative heat shield, known as PICA, the focus is not just on peak heat but also on the heat pulse that moves through the shield. If the pulse becomes too intense, it could compromise the shield’s adhesion to the spacecraft structure, potentially affecting the parachute system.

Re-entry Dynamics:

The discussion transitions to the differences between Dragon and other spacecraft in terms of lift-over-drag ratio (L/D). Musk elaborates that even gumdrop-shaped objects like Dragon have a lift vector, which can be controlled by altering the object’s orientation during re-entry. Through a series of S-turns, the landing position can be manipulated.

Orbit vs. Space:

Musk stresses the significant difference between merely reaching space and achieving orbit. He states that going to orbit and returning is around 100 times more challenging than just reaching space. He highlights that only a few countries have managed this feat, contrasting it with Bert Rutan’s achievement of reaching the edge of space without even scorching the paint of his vehicle.

Advanced Yet Makeshift Technology:

In the concluding remarks, Musk humorously observes that despite the advanced technology involved, some parts of the project appear more like “garage shop” efforts, signifying the experimental and innovative nature of SpaceX’s work.

Rocket vs. Factory Design:

Elon Musk places a heavier emphasis on the production system than on the rocket design itself. He contends that designing the rocket is relatively easy when compared to setting up an efficient production system. This is insightful because it gives a different perspective on the challenges of the space industry—production and scalability are as crucial as technological innovation.

Heat Shield Production in Florida:

SpaceX has a factory in Florida dedicated to manufacturing heat shield tiles for rockets. This factory is quite sizable and essential for producing a large number of tiles needed for each mission. Musk jokingly mentions that the factory is located next to Ron Jon’s distribution warehouse, adding a lighthearted note to the otherwise technical discussion.

Future Plans for Florida and Starship:

Elon Musk confirms that SpaceX has plans to launch the Starship from Cape Canaveral in Florida. Before that, they aim to resolve significant issues where the rockets are currently being developed. The focus is on getting the orbital version of the Starship ready before setting up further operations in Florida.

Heat Shield Tile Improvements:

Elon Musk points out that the tiles on the Starship are designed to be more uniform compared to those used in the Space Shuttle, which had 24,000 unique tiles. This is a significant improvement that simplifies both the design and manufacturing processes. Even as the shape of the rocket tapers, the tiles remain uniform, indicating a deliberate design decision aimed at efficiency.

Tile Uniformity and Reusability:

Elon Musk talks about the aim for no meaningful limit on the reusability of rockets. He also addresses the uniformity of the heat shield tiles, stating they are mostly uniform but do come in different shapes like square and hexagons. Uniform tiles contribute to easier manufacturing and potentially greater reusability.

Thermal Challenges on Reentry:

One of the most significant challenges for spacecraft reentry is the heat concentration around the hinge of the flaps. Musk points out that these parts have the highest probability of failure due to the superheated plasma that strikes them. Because these hinges have to rotate, they can’t be made entirely out of tiles, necessitating a specialized seal, likely metal, to prevent heat penetration.

Transpirational Cooling Option:

When asked about possible cooling methods, Musk brings up the idea of transpirational cooling, where fuel gas could be bled into the hinge area to counteract the heat. He also notes that burning methane doesn’t get as hot as the plasma hitting the spacecraft, making it a potential solution for thermal barriers.

Material Composition and Air Stream:

Musk gives a scientific aside about the air composition, pointing out that it’s primarily nitrogen, with only about 21% being oxygen. He indicates that even if methane burns in this air, it doesn’t get as hot as the plasma, potentially offering another layer of thermal protection during reentry.

Manufacturing Sections:

The conversation briefly touches on different manufacturing areas designated for various spacecraft components like barrel sections, nose cones, and thrust pucks, although this point is not elaborated upon.

Production Tents and High Bays:

Elon Musk discusses the changing layouts of the production tents and high bays at SpaceX facilities. These changes are a reflection of the company’s evolving focus; for example, one area is currently focused on nose cone production. He also mentions a new, higher and wider “high bay” in construction, equipped with two gantry cranes that run the full width and depth.

Booster Height and Design:

Musk talks about the height of the booster for SpaceX’s rocket. Initially set to be 70 meters, a half-barrel section was removed, making it approximately 69.5 meters. This change was made for practical reasons rather than any specific design preference. Musk dismisses the notion that there’s anything numerically special about the length; it was an arbitrary choice made easier by practical production considerations.

Control Fins and Axes:

Elon Musk addresses the control fins on their rockets, clarifying that they continuously control all three axes (pitch, yaw, and roll). Although technically only three fins are needed to control the three axes, the design maintains more fins to provide greater control authority, particularly in pitch, which requires more robust control than the other axes.

Unresolved Details and Future Plans:

Regarding the high bay bar, a planned feature in the high bay, Musk says that it is not named yet and hasn’t been a priority. He also mentions the need for an elevator upgrade from the current construction version. Both aspects indicate ongoing improvements and attention to both large-scale and nuanced elements in SpaceX’s infrastructure.

Numerical Coincidences and Philosophical Musings:

Although not directly related to SpaceX’s operations, there are moments of light banter about numerical coincidences. Musk humorously suggests such coincidences make him wonder if he’s an “avatar in someone’s video game,” showing a more philosophical and whimsical side amid the technical discussion.

Control Authority in Rocket Movement:

Elon Musk discusses the difference in control authority needed for the roll and pitch movements of a rocket. Roll requires minimal force, while pitch requires significantly more due to the necessity of pushing the rocket booster against wind resistance.

Fins and Pitch Control:

The conversation turns to the design of fins, highlighting how their placement can affect control in different axes. The closer the fins are together, similar to an X-Wing fighter, the more they contribute to pitch force. The focus here is on optimizing force in the pitch axis.

Center of Mass and Control Surfaces:

Elon uses the analogies of seesaws and wrenches to explain how the distance of control surfaces from the center of mass impacts force requirements. The closer the control surface is to the center of mass, the more force is needed to change the rocket’s angle.

Comparisons and Limitations:

The host and Elon Musk discuss the limitations of pitch control, especially in comparison with other rockets like Falcon 9 and New Glenn. Elon emphasizes that larger structures, like rockets, do not move as quickly as smaller ones, and that a precise landing does not allow for sudden pitch changes.

Terminal Velocity and Landing:

Elon mentions that the rocket will essentially come in at terminal velocity if one is aiming for a precise landing point. Due to large moments of inertia, big structures like rockets are less agile, making sudden maneuvers infeasible for precise landings.

Final Thoughts:

Elon wraps up by stating that there are many areas for potential improvements in rocket design and control. The host thanks Elon and discusses future content, while also thanking Patreon supporters for making the segment possible.