Launching a rocket is one of humankind’s crowning achievements. Each rocket is comprised of tens of thousands of small parts and components that are designed and created independently. Within the frame of the rockets that you see propelled into space, there are a number of systems that work together to ensure its smooth performance preceded by a lot of research, planning and deliberation involving the efforts of hundreds of thousands of people. While astronauts tend to be the people in the spotlight, there are numerous teams and departments, consisting of scientists, engineers, supply chain production planners, and other key personnel who take rockets from the design phase to the launch phase.
Launch vehicle capabilities (broadly speaking: payload size and thrust) have essentially plateaued, as only relatively minor incremental progress has been made in the last few decades. Materials, on the other hand, have improved significantly with the composite material innovations with mechanical properties far superior to the typical alloys that were used at the beginning of the space age. Design and manufacturing techniques have also improved, with progress in software simulation enabled by the extraordinary growth of computer power and new manufacturing methods.
Guidance and control systems have also improved thanks to advances in electronics and software. Besides the push toward green propellants, however, not much substantial has changed with solid or liquid propellants performance and related technologies, which are key to overall launcher capability.
Reusable launchers, therefore, have been a major focus area pursued by a handful of companies to reduce costs and increase launch frequencies resulting in launch costs slowly coming down. A not too insignificant portion of launch cost savings is also largely attributable to national policies and market forces, but veritable economic access to space is yet to be achieved.
Looking further out, the challenge is to develop and implement new technologies, such as hypersonic air breathing rocket engines, to be used in hybrid launchers to cut the need for large amounts of oxygen that have to be carried by current vehicles. Launch vehicles that could take off and land as aircraft, without the need for extensive and expensive service between missions, should also be developed. Similarly, in-space propulsion offers opportunities for improvement, in particular on Electric propulsion systems, which are also hybrid systems that would utilize different modes of operation.
Everyone involved in the engineering design and manufacture of parts carries significant responsibility. Moreover, the manufacturing of rocket parts and components comes with several challenges and problems. In this article, we will go through some of the most common challenges, and also present viable solutions to those problems.
Challenges and Solutions in Manufacturing Rocket Parts and Components: Why CNC Machining?
There are a multitude of space technology companies, production methods and contract manufactures involved in the design and construction of rockets, satellites and spacecraft. Starting from the beginning – It’s essential to ace the mold tool design process. The higher the precision and custom-production required, the more complex the tooling can become.
Manufacturers can achieve this high degree of precision using computer numerical control (CNC), replacing manually operated machines, vertical millers, and lathes with a computerized, automated system. CNC machines convert computer-aided design (CAD) models into mass-produced parts with as little as .0001 variation between parts. They operate via advanced manufacturing technology, removing material from a solid block using a variety of cutting tools to achieve the intended design.
The cost of building a quality stainless-steel mold tool usually constitutes the most significant financial investment in the plastic injection molding process. Because millions of plastic parts are ultimately going to be manufactured through those molds, it is important to ensure the reliability and accuracy of the mold up front in order to not have inaccuracies and faults over time. Using CNC machining to manufacture molds has many advantages that benefit the end user:
- Requires few steps to produce parts, resulting in high efficiency
- The process is more precise than manual machining and can be repeated in the same manner over and over again
- Provides the ability to produce complex shapes with a high level of precision
- Operates with advanced CAD software to produce outputs and multiple functions that cannot manually be replicated
- Fully automated systems mean that the operator is not exposed to safety risks
Advantages of CNC Machining Rocket Parts?
Milling: This process mounts the part onto a bed and removes material using rotational
cutting tools, creating products in a wide variety of shapes
Turning: This process mounts the part on a rotating chuck and removes material using
stationary cutting tools, creating axially symmetric end products
EDM: This process uses controlled electrical discharge to obtain the desired shape
CNC machining operates with many common materials including:
● Stainless steel
● Other types of metals
1. Engineering for the Right Manufacturing Materials
One of the biggest challenges manufacturing parts and components for the aerospace industry is the choice of materials. When engineering for the right material it needs to be viewed not just from the standpoint of cost but also rocket assembly and spacecraft performance. Different metals harbor different degrees of manufacturability with different alloys providing material strength variability that could withstand the extreme conditions that rockets and spacecraft must withstand.
Rocket components are subjected to extremely high forces during launch and ascent, which is why the materials used in their construction need to be strong enough to withstand those forces. Moreover, the materials used inside the fuel system need to keep the liquid fuel cool, and the ones used in the combustion and exhaust system need to be able to sustain high temperatures. Moreover, the materials need to be lightweight, so they don’t add to the overall weight of the rocket.
Oftentimes metal alloys are used as a substitute for heavy metals but certain alloys can be harder to get a hold of during supply chain crunches. While metals like chromium, cobalt, iron, and nickel are used to fulfill the requirements, manufacturers have also tried using 301 stainless steel, carbon fiber and aluminum for rocket parts, which is a promising idea. As mentioned in the previous section, there are several types of materials used in the making of rocket parts and components, each having different characteristics. However, most of the materials, especially metals, can be very expensive to use, which drives up the entire production and project cost. One such material, titanium, is highly expensive, even though it ticks all the boxes and is the perfect material for use in rocket parts manufacturing. Other less expensive materials can also be used such as 4130 and 4340 alloy steel can be used to manufacture spacecraft components, and the 2024, 6061, and 7075 variants of aluminum is strong enough to be leveraged for rocket parts fabrication. These materials aren’t only strong, but they can be molded for use in several rocket parts, however, two particular metals reign supreme: titanium and aluminum. This is due to the high strength (especially titanium) and light weight (especially aluminum) of the materials.
No industry worldwide uses more titanium alloy than aerospace due to its excellent strength-to-weight ratio, corrosion resistance and high performance standards at extreme temperatures. Titanium has become a staple material in aerospace production. In addition to spacecraft – aircraft that use large amounts of titanium for their various components include commercial vehicles like the AirBus A380 and Boeing B787, as well as military aircraft like the F-22, F/A-18, and UH-60 Black Hawk helicopter. Titanium aerospace parts include airframe and jet engine components, such as discs, blades, shafts, and casings most of which are machined. Because titanium is harder than aluminum, it can be trickier to CNC machine, causing tool wear and heat buildup. This means aerospace machining of titanium may require a reduced machine RPM and larger chipload.
Another widely used metal in aerospace machining — and one that has been around longer than titanium and modern composites — is aluminum. Aluminum alloys are lightweight and have a high tensile strength. Aluminum forms an oxide coating when exposed to air, making it corrosion resistant, and it is also highly formable (more so than titanium), making it easy to CNC machine. In aerospace CNC machining, the most common aluminum alloy is aluminum 7075, whose main alloying element is zinc. Though not as machinable as other alloys, 7075 has excellent fatigue strength. Many wing, fuselage, and support structure components are made from this material. Other machinable aerospace aluminum alloys include 4047 (cladding/filler), 6951 (fins), and 6063 (structural). 6000-series alloys are generally considered more machinable than others.
The Special Metals Corporation has developed a range of austenitic nickel-chromium-based superalloys called Inconel. One particular grade of the material, Inconel 718, was developed specifically for aerospace applications. One of its first high-profile uses was for the jet engine diffuser case (an extremely high-pressure part that joins the compressor to the combustor) of the Pratt & Whitney J58 engine, which was used in vehicles like the Lockheed SR-71 Blackbird. Inconel 718 has more recently been used by Elon Musk’s SpaceX in the engine manifold of its Merlin engine, powering the Falcon 9 launch vehicle. It is also found in other aerospace components like turbine blades, ducting systems, and engine exhaust systems. As a work-hardened metal, Inconel 718 must be machined using as few passes as possible; machinists typically deploy an aggressive but slow cut using a hard cutting tool. The superalloy has good weldability, however.
2. Challenges Machining and Fabricating Steel
Whether you have challenging parts to burrs, slag, bumps, sharp edges, raised edges, seams or oxide that need to be removed after forging, stamping, drilling, welding, cutting, slitting, machining, molding, and casting? Those industrial procedures often render an uneven surface, which is modified and smoothened using suitable deburring machinery.
Deburring machine is a valuable investment for nearly any manufacturer, especially steel fabrication and machining processes. Systems are engineered to provide you with good aesthetics and quality deburring and finishing.
● Dry operation.
● Max. deburring and finishing widths of 600mm, 800mm and 1000mm. Processing thickness up to 60mm
● Metal precision pre-grinding, drawing, polishing, scratching, deburring, chamfering, etc.
● Stainless Steel, iron plate, Aluminum, Brass, Copper, iron plate and other alloy steels, where finishing is required with deburring operation.
● Wide abrasive belt and universal roller brush single or multiple combination structure.
● Abrasive belt grinding station for the big burrs pre-removal, edge rounding and surface finishing at one pass.
● Rotating brush can do deburring on all edges and deeply in holes on plate.
● Burrs on interior and exterior contours can be all removed.
● Vacuum adsorption conveyor feed table with self-cleaning air device for holding the small parts.
● The CNC touch screen can set the processing parameters.
3. Complex Angles and Machining Difficult-To-Reach Areas Using The Cutting Head
Another challenge in rocket parts manufacturing is the involvement of complex and difficult angles, which are common in the spacecraft industry. When it comes to CNC machining spacecraft components, a huge emphasis is placed on reducing their weight, increasing strength and durability, maximizing airflow, and other purposes.
5 axis CNC machines are extremely versatile manufacturing centers that can utilize up to five different axes simultaneously. There are three linear axes and two rotational axes. Their capabilities are significantly more varied than those of standard 3-axis CNC machines. 5 axis machines can be configured to eliminate multiple setups, reducing the need for continuous supervision, increasing productivity, and achieving single-setup machining. A 5-axis machine is a powerful tool in any machine shop. It is capable of creating complete parts without requiring any setup changes by a skilled operator, so it can 3reduce downtime to a minimum.
The limited amount of re-fixturing required by 5-axis CNC machines makes them ideal for the aerospace industry. An aerospace component is typically complex, so 3 or 4 axis CNC machines require multiple re- fixturing steps and re-orientations to allow the cutting head to reach difficult to reach areas. In addition to organic shapes, aerospace components have compound curves that are ideal for 5-axis machines. Compound curves can be found in turbine blades, which are cast and typically machined on a 5-axis machining center to achieve the desired shape and finish.
4. Special Operations CNC Machining Large Rocket Parts
Another type of geometry challenge faced in large spacecraft component CNC machining is the requirement for large-sized parts, which exceed the production capabilities of your CNC machines. Although most of the components made for rockets are small and minute, the frames and housing for several systems and components are much larger, and some of them also need a single and seamless construction.
When machining large rocket parts, several components require hollow cavities, such as the rocket engine housing. This requires manufacturers to hollow out several materials, which has to be done through the CNC machine. This is where the real challenge lies: not only does this cause a lot of time to be spent, it also generates a lot of wasted material, which needs to be disposed of properly.
Moreover, using the CNC machine for hollowing out the material puts excessive pressure on the part being manufactured. This pressure is also called residual stress and it also causes the manufactured rocket parts to get deformed or warped. It can be a major issue, especially if the part has little or no tolerance. It can also cause the rocket part to be rejected on the basis of quality.
There is an effective solution to this problem as well. There are certain formula that can be used to determine how much material will be removed, known as the Internal Removed Material Ratio (IRMR) and External Removed Material Ratio (ERMR). The IRMR shouldn’t be lower than 85%, while the ERMR should be higher than 30%. One way in which manufacturers can work around this is to fabricate one part and check it before resuming production.
If you don’t have a CNC machine that can produce larger parts, you might be at a disadvantage. However, you can navigate around the situation by finding a rocket parts fabrication expert that contains large CNC machines and can easily handle the part sizes you need. Otherwise, you can manage the production by breaking down the component design into smaller parts, or you can use casting as a method to produce larger components in one piece. If you use casting, you will still a CNC machine to finish the components.
5. Small Quantity Variable Lot Rocket Parts Production
Space Exploration technology, spacecraft and rocket development are still in their nascency and dont tend to be mass produced. Although aerospace components are in high demand, rocket parts aren’t ordered in quantities of more than a few hundred, which can pose a cost and timing challenge for many suppliers and manufacturers.
This is where tradecraft and toolcraft factor heavily into the ability to turn variable lot complex parts quickly within the tight timeframe requirements of spacecraft assemblers. Ample experience with machine programming setup and tooling will be a major asset for deploying agile production methods to achieve industry requirements.
6. Aerospace machining certifications
Aerospace CNC machining is a critical procedure that leaves no room for error. Where some industries allow for variable tolerances and material variations, aerospace demands total precision and consistency in order to guarantee human safety. Different applications and parts must meet rigorous standards and certifications many of which are US specific standards as well as some international ones.
One particularly important certification applicable to many applications is the AS9100 certification, an SAE international standard awarded to suppliers that is described as a “Model for Quality Assurance in Design, Development, Production, Installation, and Servicing” in aerospace. An extension of ISO 9001, the AS9100 certification is not required for all aerospace part production, but customers may seek out suppliers with the certification to guarantee quality.
Other important certifications for aerospace machining include ITAR (International Traffic in Arms Regulations), a set of guidelines by the US State Department outlining US requirements for selling and producing technology on the US Munitions List, and AS9102 First Article Inspection Reports, which indicate compliance with the verification requirement aerospace parts.
Whether you work in a rocket, satellite or spacecraft commercial enterprise or startup, we understand your need for timeliness, precision and quality. There is a lot at stake when spacecraft are being assembled on strict build schedules preparing for commercial launch payload delivery. when you are faced with challenges in your rocket parts supply chain, Syncfab can help. We offer a wide range of mission critical supply chain services, including the our core digital procurement of custom spacecraft component parts production, as well as compliance, traceability, mission assurance, and much more.