New spacecraft experience setbacks all the time. SpaceX Starship prototype violently disassembled several times. Boeing launched the CST-100 but ended up in the wrong orbit. China isn’t a stranger to setbacks either.
China tested a prototype spacecraft on May 5th, 2020 in efforts to prove the technology was ready. It’s good it was a test and not an actual mission since the spacecraft did not perform as expected. The news agency Xinhua reported the spacecraft launched from Hainan China, operated abnormally during its return.
Heat Shields Need to work or expect a terrible day.
Spacecraft experience tremendous heat during the last minutes of their mission. The heat shield protects the spacecraft from that heat. NASA looked at lots of materials and tested many before using for heat shields.
NASA’s Space Shuttle used a thermal soak heat shield approach. The Shuttle tiles act as an insulating material. The design absorbs and radiates the heat away from the spacecraft structure. A second common approach is an ablative heat shield like those used for Mercury, Gemini, Apollo, and Orion spacecraft. These ablative heat shields commonly have a layer of plastic resin which experiences intense heating while entering the atmosphere. The heat shield wears away, carrying the heat away through convection.
If damage to the heat shield results in compromised performance, disaster can strike like the loss of the Space Shuttle Columbia and all crew aboard. With Columbia, during takeoff, the heat shield tile damage occurred. While returning to Earth, super-heated gasses snuck in through the damaged tiles and resulted in the accident.
Newer heat shield design strives to increase reliability and safety. NASA developed the Phenolic Impregnated Carbon Ablator (PICA) heat shield. SpaceX continued to develop and adopted the technology for a segmented 3.6-meter PICA-X shield used on its Dragon spacecraft. SpaceX shared that PICA-A’s usefulness potentially extends for hundreds of times for Earth orbit reentry with only minor degradation each time. This performance allowed NASA’s Stardust comet sample return mission to survive reentry from its deep-space mission.
Low Earth Orbit reentry generates less heat than reentry from deep space. The entry velocity for NASA’s Stardust capsule was greater than the Apollo Moon missions. The faster the velocity, the more heat generated. Don’t let the numbers fool you. The energy goes up drastically with speed. (Remember E = ½ m ∙ v2 ). The head shield needs to withstand the heat generated from dissipating this excess energy.
Stardust: inertial velocity of 12.9 km/s
Apollo Lunar Missions: 11.0 km/s
The Space Shuttle: 7.7 km/s
Safe reentry depends on shields that can even withstand the much higher heat generated from the high velocity from a moon or Mars velocity reentry. It takes time to prove these technologies. NASA developed the technology for years before using its Stardust mission. SpaceX 4 year adaption of the PICA technology was a fraction of the time that NASA originally expected, but the development still took years. Through testing and diligence, these new technologies mature into a TRL-9.
The NASA nine-point scale in use:
TRL 1 – Basic principles observed and reported
TRL 2 – Technology concept and/or application planned
TRL 3 – Analytical and experimental critical function and/or characteristic proof-of-concept
TRL 4 – Component and/or breadboard validation in the laboratory environment
TRL 5 – Component and/or breadboard validation in the relevant environment
TRL 6 – System/subsystem model or prototype demonstration in a relevant environment (ground or space)
TRL 7 – System prototype demonstration in a space environment
TRL 8 – Actual system completed and “flight qualified” through test and demonstration (ground or space)
TRL 9 – Actual system “flight-proven” through successful mission operations
China developing new heat shields.
The prototype spacecraft is one of the multiple new spacecraft China plans to use for its future space plans. China became the third nation to send people to space using the Shenzhou spacecraft to do that. They derived the Shenzhou spacecraft from the Russian Soyuz spacecraft. This spacecraft along with a cargo spacecraft served China well for the first twenty years of its human spaceflight program. Like the USA, China aspires to do deep-space missions that necessities improvements on that existing technology. Sample return missions from the Moon, Mars and deep space human spaceflight need reliable heat shields. China did not share a lot of details in the press release, but it is clear they are testing inflatable space technology.
To ensure that the technology is ready for adoption, they conduct multiple tests. Each round of testing progressively moves the technology closer to maturity and eventual adoption into active spacecraft. According to the reports from Xinhua news, the new Chinese spacecraft intended to prove out different technology leveraging a flexible and inflatable cargo return capsule rather than a traditional heat shield.
Recall there is a lot of energy to dissipate which translates into heat. If a spacecraft can use a larger surface area, then the heat generated spreads out over a larger area. With traditional rigid heat shields, it fixes the spacecraft surface area. To increase the mass of the heat shield means a larger, more expensive rocket. As an alternate to a larger rocket, the spacecraft can stow less other equipment and cargo. The inflatable heat shield could be a design improvement for certain missions. With inflatable heat shields, the spacecraft can increase the area to shed excess heat. The concept allows for the increased area with a minimal increase in mass.
China isn’t the only country developing this technology. NASA’s Technology Demonstration Missions seek to mature emerging technologies. The program focuses on technological innovations to overcome current limitations from use. One of these programs is NASA’s Inflatable Heat Shield Technology, formally known as the Low Earth Orbit Flight Test of an Inflatable Decelerator(LOFTID). If successful they would use the technology for more robust missions to destinations like Mars, Venus, and Titan enabling sample return. Even payloads from the space station or deep space gateway could leverage this game-changing technology.
Potential use for this technology is the recovery of expensive rocket engines, which represent 66% of a typical first-stage rocket booster’s cost. Companies like ULA are looking to leverage technology to recover reusable engines from ULA’s next-generation Vulcan rocket. NASA could seek to retrofit the SLS and recover the 4 RS-25 engines used on the first stage of the mega-rocket. NASA pays Aerojet over 100 million dollars each for the RS-25 engines and uses four for each disposable first stage. Potential cost savings of $400 million per launch are if NASA could adapt this technology and provide minimal mission impact. The tradeoff of mass on the first stage is much less than the tradeoff of a second stage, so recovering most of the rocket cost would be an excellent upgrade(for single-use rockets). Read more about NASA’s Mega cost rocket.
The testing of China’s inflatable space tech shows how dedicated China is towards maturing in this field. NASA targeted an initial orbital demonstration flight on an Atlas V rocket launch in 2022. China’s attempt to test out this earth-shattering technology two years before NASA’s orbital test represents a proliferation of new-space ideas coming to age.
China’s Second Academy of the China Aerospace Science and Industry Corporation developed the concept spacecraft to be a novel space transport vehicle. The news report shared little details except that it developed the cargo return capsule to be flexible and inflatable. The original plan included the experimental spacecraft returning to Earth on Wednesday, May 5th.
When successful, this breakthrough technology could drastically lower the cost of space travel. It is no wonder that both the USA and China are working on this space tech. It will take more time to mature this technology to TRL9, and when it gets there, expect exciting things.
About The Author
Bill D’Zio
Co-Founder at WestEastSpace.com
Bill founded WestEastSpace.com after returning to China in 2019 to be supportive of his wife’s career. Moving to China meant leaving the US rocket/launch industry behind, as the USA and China don’t see eye to eye on cooperation in space. Bill has an engineering degree and is an experienced leader of international cross-functional teams with experience in evaluating, optimizing and awarding sub-contracts for complex systems. Bill has worked with ASME Components, Instrumentation and Controls (I&C) for use in launch vehicles, satellites, aerospace nuclear, and industrial applications.
Bill provides consulting services for engineering, supply chain, and project management.
