“We never dreamt that it would be this clear, this beautiful.” – said J.T. Heineck of NASA’s Ames Research Center upon taking a first glimpse at the first air-to-air images of the supersonic shockwave interaction in flight. As cool as the images look, capturing them is not easy and took about a decade in the making.

NASA was able to get the first air-to-air photos of the interaction of shockwaves from two supersonic aircraft flying in formation using the schlieren photography technique. These two T-38 aircraft from the U.S. Air Force Test Pilot School are flying in formation at a distance of around 30 feet while traveling at supersonic speeds, which is faster than the speed of sound, creating shockwaves that can be heard on the ground as a sonic boom. The King Air, flying a pattern at 30,000 feet, had to be in a perfect position as the two T-38s went by at supersonic speeds around 2,000 feet below to get these pictures. The cameras had a three-second maximum recording time and had to start filming as soon as the supersonic T-38s entered the frame and snapped their trek through the sound barrier at 1,400 frames per second. The pictures were taken during a supersonic flight series performed, in part, to better understand how shocks interact with aircraft plumes as well as with each other. The images were initially monochrome and are now displayed as colorized composite images.

Aircraft traveling faster than the speed of sound produce shock waves. These waves combine to produce a sonic boom, which is a loud bang. NASA anticipates that its study will help shape the design of the X-59 QueSST, a quiet supersonic aircraft that will begin test flights in 2022. Scientists may be able to improve the X-59 such that it will only make a slight sound when it breaks past the sound barrier using the additional data points. If the research is successful, it may aid in the burgeoning resurrection of supersonic airplane technology: Due to the sonic boom issue, the Concorde, the most well-known commercial supersonic aircraft, was only allowed to break the sound barrier while it was over water. Yet, if the X-59’s quieter technology holds up, it may help save supersonic aircraft from extinction.

Source:

https://www.nasa.gov/centers/armstrong/features/supersonic-shockwave-interaction.html

https://www.popularmechanics.com/flight/a26721418/nasa-sonic-shockwave-photos/

The Stratospheric Observatory for Infrared Astronomy (SOFIA) telescope, NASA’s flying observatory, has now retired after its last flight that took off from the Palmdale regional airport in California at 9:14 a.m IST on September 29, flew around the North Pacific Ocean for seven hours and 58 minutes, and landed at 5:05 p.m. IST.

SOFIA, which has been in operation since 2014, is a modified Boeing 747SP jetliner, registration N747NA, that carries a 17,000-kilogram, 2.5-meter-wide telescope donated by the German Space Agency’s Deutsches Zentrum für Luft- und Raumfahr (DLR). This telescope was used to study the infrared universe and keep track of occasions like the formation of new stars and solar systems.

The development of the SOFIA mission started in 1996. Although its first flight occurred in 2010, it didn’t reach full operational capability until 2014. After completing its five-year primary mission between 2014 and 2019, SOFIA received a three-year extension. It conducted observations of the Moon, planets, stars, and more during this time, helping to pave the way for the 2020 lunar water discovery.

READ | Airborne Observatory

For many years, SOFIA has been a unique aircraft that has traveled the globe while gathering data for research into the universe. The NASA Armstrong Flight Research Center in Palmdale, California, has been responsible for the aircraft’s maintenance and operation. Sadly, NASA unveiled the end of SOFIA earlier this year after finding that the mission’s scientific productivity did not outweigh its operating expenses, according to a report.

SOFIA’s main discoveries

SOFIA made some exciting discoveries during its lifetime, including the discovery of water on the Moon’s sunlit surface in 2020. Water molecules (H2O) were detected by the observatory in Clavius Crater, one of the largest craters visible from Earth, located in the Moon’s southern hemisphere. This modified Boeing 747SP jetliner flies into the stratosphere at 38,000-45,000 feet and lands after each flight so that its instruments can be exchanged, serviced, or upgraded to harness new technologies.

READ | The 747 that carried America’s space dreams

SOFIA’s before retiring

SOFIA had an intriguing 2022. According to FlightRadar24.com, the 44-year-old aircraft flew 143 times. NASA used the ‘Queen of the Skies’ on flights primarily from Palmdale, but also from Santiago, Chile (SCL) and Christchurch, New Zealand (CHC). It was SOFIA’s first and only mission in South America when it visited Santiago de Chile. The telescope was deployed in Chile for two weeks to observe celestial objects visible only from Southern Hemisphere latitudes.

SOFIA flew to New Zealand in June. The 747 was supposed to stay for more than a month, flying several science missions. The 747SP, on the other hand, was damaged by a storm on July 18. High winds caused the stairs outside the aircraft to shift during the storm, causing damage to the plane’s front.

Following this incident, SOFIA returned to Palmdale and continued to operate several flights in California. NASA has expressed gratitude to the hundreds of people in the United States and Germany who have contributed to the SOFIA mission over its lifetime.

Pleasingly, NASA said in a statement earlier this year when it announced the end of the mission, that SOFIA’s data will be available for use by astronomers worldwide in NASA’s public archives.

SpaceX is now quite used to landing their rebuilt rockets with ease. The 23^rd of July 2022, marked their 56^th first stage landing of the Falcon 9 successfully. Gone are the days of building new boosters for each new mission and here are the days when it just takes days for SpaceX to refurbish and reuse their rockets. Quite a remarkable achievement, isn’t it? All of this may seem easy on paper but is it really in reality? Let’s get one thing straight. It is not easy to have something land on its own using computer systems onboard. The landings of the Falcon 9 look jaw-dropping and staggering from earth but what goes behind it? Let’s find out.

It is incredibly difficult to launch a Falcon 9 rocket into space and then return the first stage booster to Earth in a vertical landing, despite the company’s 80 percent success rate for rocket landings. The end of a fourteen-story aluminum-lithium alloy tube that is exploding with fire doesn’t merely find a comfortable landing in a massive empty field. The first stage’s most noticeable features are its cold gas maneuvering thrusters and aluminum or titanium grid fins, both of which are intended to give the first stage some degree of control and agility during its journey both inside and outside of Earth’s atmosphere. A lot of science behind each step.

Onboard Computers

High-accuracy GPS, gyroscopes, and accelerometers are integrated into the booster and are located at both the top and bottom end to accurately determine orientation, location, and velocity. Additionally, the booster has a large number of strain gauges that track forces acting on the structure at important points, including engine thrust. The onboard computer uses this information about the rocket’s orientation, location, velocity, acceleration, and altitude to perform the appropriate flying changes so that the rocket can make a clean vertical landing during re-entry. On GPUs, the computers process several physics equations that are then utilized to compute errors, regulate thrust vectoring, grid fin locations, and cold gas thruster (Nitrogen gas thrusters) durations, as well as optimize the flight path.

Boost-Back Burn

The booster is initially turned end-for-end while performing a boost-back burn. For a landing on a drone ship or near the launch point, the burn changes horizontal velocity. The reentry burn serves as a second chance to fix any reentry path errors while also reducing air velocity to prevent the rocket from being damaged by reentry heat. Hydraulic actuators are used to gimbal the Merlin engines of the Falcon 9’s first stage booster, allowing the rocket to change the direction of its thrust.

Grid Fins

Waffle-shaped grid fins extend that move the center of pressure of the booster upwards, increasing aerodynamic stability. The grid fins are arranged in the shape of an X-wing, stowed during ascent, and then deployed during reentry. The fins, which have a footprint of just 4 by 5 feet, are nonetheless able to roll, pitch, and yaw the 14-story stage up to 20 degrees to aim for a precise landing.

Landing

In between the re-entry and the landing burn, the booster spends a lot of time falling through the thick atmosphere. During these two stages, the booster’s slowdown from hypersonic speeds to transonic speeds all within a few seconds. The Falcon 9 actively modifies its orientation both inside and outside of the Earth’s atmosphere via thrust vectoring. The landing burn is sequenced with one, three, and one engine(s) running to reduce fuel usage. The Merlin engines are re-ignited when the booster is about to land. Upon re-ignition, landing lights and deployable landings legs are deployed that are a sequenced rehearsal for all booster landings.

Deployable Legs

A four-legged deployable landing gear comprised of durable, lightweight carbon fiber and aluminum are fitted on the Falcon 9. Just before touchdown, high-pressure helium is used to deploy the legs. To soften the landing, each leg is equipped with a shock-absorbing system.

Drone Ship

Launch sites for the Falcon 9 are located close to the ocean. Therefore, the first stage booster is bound towards the ocean when it returns to Earth following separation. These football-field-sized drone ships allow the Falcon 9 to land on the water, especially when a Falcon flight is headed for geostationary orbit. ‘Just Read the Instructions’ and ‘Of Course, I Still Love You’ are two drone ships that SpaceX currently uses during launches from Cape Canaveral.

Sources

https://www.asminternational.org/web/hts/videos/-/journal_content/56/10192/36857184/VIDEO

https://www.inverse.com/article/33904-how-spacex-lands-a-falcon-9-rocket-in-6-steps

https://medium.com/predict/how-spacexs-rocket-boosters-land-on-earth-c46694a6ef99

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