Elon Musk explains Falcon 9 Block 5 which carried Bangabandhu-1: Take a look

New Delhi : It was a few days back when SpaceX CEO Elon Musk came forward to explain all the improvements experienced by latest version of the Falcon 9. His speech mentioned details including redesigning a pressure vessel which was associated in the explosion of rocket in 2016.

In a press brief, Musk said the Block 5 is designed to be "the most reliable rocket ever built."

"That is the design intent," he said. "I hope fate doesn’t punish me for these words, but that is unequivocally the intent. And I think our most conservative customers would agree with that." 

Elon said that a last-minute hassle on May 10 postponed the Block 5 Falcon 9's debut launch 24 hours to May 11. SpaceX blamed "a standard ground system auto abort" for halting the countdown 58 seconds before liftoff. The rocket lifted off successfully May 11 at 4:14 p.m. EDT, landed its first stage 11 minutes later and positioned Bangladesh's first telecom satellite, Bangabandhu-1, to geostationary transfer orbit just under 34 minutes later.

Musk said the scientists at SpaceX put their best effort into creating extremely reliable COPVs, or composite overwrapped pressure vessels, used to store helium to pressurize the propellant tanks in the launcher's second stage.

 In September 2016, a Falcon 9 exploded during preparations for a static fire test and destroyed a telecom satellite for Israeli fleet operator.

SpaceX found the cause to liquid oxygen in the upper stage tank that got entrapped between the COPV overwrap and liner and ignited either from resistance or other mechanisms. SpaceX has since worked to redesign those pressure vessels in support with NASA in order to address the agency's concerns about using that design on later Falcon 9 commercial crew launches.

"This is by far the most advanced pressure vessel ever developed by humanity," Musk said. "It's nuts. I've personally gone over the design; I can't count how many times. The top engineering minds at SpaceX have agonized over this … I think we are in a good situation."

Musk said the COPVs now have a burst pressure "more than twice what they are actually loaded to on the pad." SpaceX has a contingency design that would involve switching from high-strength carbon fiber with an aluminum liner to the superalloy Inconel, but that is "unlikely to be necessary," 

While it’s the fifth iteration of the Falcon 9, Musk said the Block 5 "is arguably Falcon 9's version 6" based on how improvements have been made over time.

"The word 'block' is a bit strange. We kind of adopted it from the Russians," he said.

Musk said the each of the nine Merlin engines used to power the Falcon 9's first stage now have an 8 percent increase in thrust at sea level to 190,000 pounds-force. The single vacuum-optimized Merlin engine on Falcon 9's second stage has a 5 percent thrust increase to 220,000 pounds-force, he said.

In comparison, the Block 5 Falcon 9 is twice as powerful as the Falcon 9 that first launched a demonstration resupply mission for NASA in 2010. The Merlin engines on that first version had 95,000 pounds of thrust for each first-stage engine and 92,500 pounds of thrust for the second-stage engine.

The first stage of Block 5 rockets are designed to be far more reusable than previous versions which so far have only flown twice before retirement.

"In principle, we could refly Block 4 probably upwards of 10 times, but with a fair amount of work between each flight," Musk said. "The key to Block 5 is that it's designed to do 10 or more flights with no refurbishment between each flight. The only thing that needs to change is to reload propellant and fly again."

With some refurbishment, a Block 5 first stage should be able to launch 100 times, Musk said.

In addition to greater reusability, SpaceX's Block 5 Falcon 9 is designed to meet NASA commercial crew requirements and Air Force national security launch criteria. It's also designed for easier manufacturing.

Musk said the Falcon 9's octaweb structure, supports all nine first stage engines and provides compartmentalization in case one or more fails, is now much stronger. The octaweb is made with bolted instead of welded aluminum and has greater thermal protection to prevent melting, he said.

Musk said the rocket's interstage features a hydrophobic thermal protection developed by SpaceX that is highly reusable and doesn't require paint. Placed between the first and second stages of the rocket, which are painted white, the jet-black carbon fiber interstage harkens back to SpaceX's first rocket, the Falcon 1.

"Obviously, aesthetics are a minor factor in rocket design, but I still like the fact that we've returned for nostalgic reasons to having a black interstage," Musk said.

"There will not be a Block 6," Musk said. "We intend to stabilize on the Block 5 platform and have no major upgrades."