The first Falcon 9 Block 5 is transported to the launch pad at Cape Canaveral. Source: SpaceX

Rocket launch company SpaceX continues its push for affordable access to space, driven by CEO Elon Musk’s belief that humanity must become a multi-planet species to preserve the light of consciousness in the event of a catastrophe occurring on Earth. To realize that goal, the company has been iterating on the design of its primary launch vehicle, the Falcon 9, in an effort to improve its reusability.

SpaceX’s Falcon 9 rocket with a reused first stage currently costs around $50 million, down from the $62.5 million list price posted on the company’s website. Musk said the price could eventually be reduced to under $5 million by recovering and reusing all major components of the rocket.

A Falcon 9 Block 5 rockets sits on the pad at Vandenberg Air Force Base on July 24, 2018 one day prior to the launch of ten Iridium NEXT satellites for the Iridium-7 mission. Source: SpaceX

Block 5

The latest version of the Falcon 9, referred to as “Block 5,” represents a significant step toward that target. Block 5 incorporates a number of design refinements aimed at dramatically improving the rocket’s reusability. It is designed to fly at least 10 times without needing any maintenance work other than refueling.

With less downtime required between flights, SpaceX aims to accelerate Falcon 9’s launch cadence. By the end of 2019, the company hopes to launch, land and refly the same Block 5 rocket within 24 hours. SpaceX expects that with occasional refurbishment, Block 5 boosters are capable of completing over 100 flights before retirement. The previous iteration of Falcon 9 was only capable of flying two or three times before being deemed unfit for flight.

SpaceX invested significant engineering effort into Block 5’s design, taking into account the plethora of flight data and lessons learned from Falcon 9’s fairly extensive flight history of over 50 launches. Engineers reviewed nearly every aspect of the rocket’s performance and made hundreds of improvements across the vehicle, adding more durable valves and additional sensors to monitor the rocket’s health.

Surviving the Heat

Many of the enhancements were aimed at bolstering the rocket’s ability to withstand the extreme temperatures of atmospheric re-entry, in which the friction of air rubbing against a vehicle speeding at over 1,600 m/s generates tremendous heat.

Block 5 is equipped with new thermal protection technology consisting of a waterproof material that is immune to both high temperature and moisture. It permanently covers the rocket’s interstage, raceways and landing legs, replacing a coating of paint on previous Falcon 9 iterations that required restoration after each flight.

The Block 5’s titanium grid fins were in good shape following the Falcon 9’s first stage landing on one of SpaceX’s drone ships at sea during the successful Iridium-7 NEXT mission on July 25, 2018. Source: Teslarati / Pauline Acalin

The grid fins that steer Falcon 9’s first stage to a controlled landing are now made of uncoated titanium instead of painted aluminum. These fins are the largest titanium forgings in the world and feature improved thermal performance capable of withstanding over 1000° C. Unlike previous aluminum fins which often required replacement after partially melting during reentry, the new titanium fins are expected to last the entire lifespan of the rocket.

Octaweb Upgrade

The aluminum octaweb structure that supports the rocket’s nine Merlin 1-D engines also received improved thermal protection. The heat shield surrounding the octaweb at the base of the rocket, previously a composite structure, has been replaced with titanium with a higher melting point that doesn’t require replacement. Parts of the shield will have active water cooling to handle hot spots generated by hypersonic sharp-shock impingement during atmospheric re-entry.

The octaweb itself is now constructed with a higher strength 7000 series aluminum instead of the previous 2000 series material. It is also bolted together instead of welded, reducing the time required to inspect and refurbish the Merlin engines.

Upgraded landing legs reduce the Block 5’s reflight time thanks to an internal latch mechanism that allows the landing gear to be easily deployed and stowed, saving several hours in the stowing process compared to the old design.

The heat shield protecting the octaweb that supports the nine Merlin 1-D engines at the base of the Block 5 is visible in this image as SpaceX technicians inspect the rocket after successful completion of the Iridium-7 NEXT mission. Source: Teslarati / Pauline Acalin

Full Potential

The rocket is now capable of carrying a higher payload to orbit with more powerful first stage Merlin 1-D engines generating a full 190,000 lbf of thrust at sea level – an 8% improvement with the potential for an additional two percent thrust increase in the future. The second stage vacuum Merlin has room for a five percent thrust improvement to 220,000 lbf, although SpaceX will operate it for now at 210,000 lbf as the company analyzes data from the first few flights of the Block 5.

Updated avionics – including a new inertial measurement system, engine controllers and flight computer – increase the rocket’s tolerance to faults, making catastrophic failure less likely in the event of component malfunctions.

To address NASA’s concern about the rocket’s composite overwrapped pressure vessels (COPV), SpaceX redesigned them to withstand twice the burst pressure of the actual load. A COPV containing high-pressure helium immersed in the second stage liquid oxygen tank caused a spectacular explosion in the failed Falcon 9 mission to launch the Amos-6 Israeli Earth communications satellite on Sept. 3, 2016. The redesigned COPVs – made of high-strength carbon fiber with an aluminum liner – have gone through extensive testing. Should any problems occur during operational missions, a backup plan exists to switch to an Inconel sphere design.

Ultimate Reusability

SpaceX lowers a previously recovered fairing half into the net attached to fairing recovery ship Mr. Steven to test the net and its supporting structure. Source: Teslarati / Pauline Acalin

SpaceX is also working toward full reusability of both the fairing that encloses the payload at the top of the rocket and the second stage that boosts the payload into orbit on the final leg of the launch. The company is endeavoring to perfect a plan to guide each fairing half with a parafoil to a gentle landing in a giant net attached to a ship in the ocean. For the second stage, SpaceX will start gathering telemetry data on its health as it re-enters the atmosphere during future missions. In addition, thermal protection will be gradually added to the upper stage to determine the minimum amount of shielding necessary to recover it in a reusable condition.

The majority of the price of a Falcon 9 launch is attributable to manufacturing. The rocket’s first stage represents 60% of the cost, the second stage is 20% and the fairing is 10%. Only the last 10% of the price tag is due to recurring costs associated with every launch, including fuel and operations.

If SpaceX achieves its goal of reusing every major component of the Falcon 9 Block 5, spreading the rocket’s fabrication cost over more than 100 launches, the company might very well lower the cost of a Falcon 9 launch to a mere $5 million, revolutionizing access to space.