Two months ago, on May 30, Bob bunken and Douglas Hurley, two NASA astronauts, became the focus of the world’s attention. They took the SpaceX manned dragon spaceship and launched from the Kennedy Space Center 39A. After a 19 hour long journey, they successfully arrived at the international space station.

the main responsibility of benken and Hurley is to carry out the test task code named “Demo 2”. From the launch to the docking of the space station, and then to the return journey in the reentry module, the two men need to monitor the SpaceX manned space system.

in the dome cabin of the space station, Hurley captured the blue earth with the shutter through six bright windows. From day to night, he uploaded his photos to Twitter and shared them with the world.

two months’ wandering in space is undoubtedly a long time. At 7:35 Beijing time on August 2, benken and Hurley steered the Dragon spacecraft to separate from the international space station.

after leaving the space station, the Dragon spacecraft will have to circle in orbit for 18 hours. After that, the thruster was turned on and left the orbit to enter the earth’s atmosphere. During this period, the extreme temperature of 3500 degrees Fahrenheit was experienced, and the safety performance of the external heat shield of the spacecraft was greatly tested.

assuming that the weather conditions are not ideal, NASA and SpaceX will delay the derailment ignition of the manned dragon spacecraft. NASA staff said supplies on the manned Longfei ship could last three days.

fortunately, the Dragon spaceship of the two astronauts successfully entered the atmosphere and the parachute opened. At 2:48 Beijing time on August 3, the Dragon spacecraft splashed down successfully in the Gulf of Mexico.

different from the amazing vertical landing in the recovery process of SpaceX rocket booster, the Dragon spacecraft adopts the most traditional and conservative reentry and return mode, that is, parachute splash down at sea.

in the initial design of the manned dragon spacecraft, in addition to meeting the basic principles of reusability and recyclability, the soft landing return mode of booster is also the most eye-catching standard design of the spacecraft. This is basically equivalent to the technical principle and presentation effect of Falcon 9’s vertical landing.

the original design of the manned dragon spacecraft was ignited by the superdraco engine for a vertical landing. This is a photo of the prototype test ignition SpaceX

but when SpaceX handed the proud design to NASA in 2017, it met with firm resistance. Because if these new functions of the manned dragon spacecraft are integrated, there will be too many uncertainties.

although there were no accidents in the tests of propulsion suspension, launch suspension, escape and vertical landing of the Dragon spacecraft, the doubts of NASA’s decision-makers were not eliminated.

like most people, they believe that technological innovation is obviously less important than the safety of manned space flight. After all, NASA was so frightened by two previous space shuttle accidents that it had to be conservative.

of course, SpaceX also values the safety of astronauts. Booster landing was originally the best way for SpaceX to land on Mars, but it needs to guarantee the quality from the safety point of view. SpaceX eventually changed its mind and canceled the landing function of Longfei booster.

the final design demo of the manned dragon spacecraft cancels the design of the landing frame, but still retains the configuration of superdraco engine, which is used to realize the emergency escape function during launch. Although the manned dragon spacecraft castrated by SpaceX

still retains the booster, it cuts off the landing frame. The alternative landing options are parachute splashing and maritime search and rescue that we see today.

although the return process of parachute splashing is not as shocking as the scene of launching, it is far more difficult than launching. Because the Falcon rocket, which depends on the launch, has been recognized in the high-frequency launch of the past three years, both in terms of carrying capacity and reliability.

first of all, when the manned dragon spacecraft leaves orbit and enters the atmosphere, it will rub with the air and generate huge heat, up to 3500 degrees Fahrenheit. This is a huge challenge for the spacecraft’s thermal protection system, which is one of the tests, of course.

secondly, the overload environment and vibration environment are also a kind of test for the electrical control system on board. The high temperature will cause communication interruption between the spacecraft and the earth, which is expected to last for about 6 minutes. Therefore, the reentry angle of the spacecraft return module must be well controlled.

when the Dragon spaceship leaves the regulations and enters the atmosphere, the return module of the Dragon spacecraft will rub with the air to generate huge heat, up to 3500 degrees Fahrenheit

in the past, almost all spaceships landed on land. The reason why the Dragon spacecraft does not land on land is that SpaceX takes into account the large deviation of landing point caused by meteorological wind field and other measurement errors. Landing on the sea obviously doesn’t have to worry about the safety of the people on the ground.

Aerospace can’t always be cool. Although the reverse thrust vertical landing of the engine can provide excellent accuracy of the impact point, the cost is that the reliability of the reverse thrust engine is required to be very high, once the problem occurs, the consequences are unimaginable.

in fact, the mission of “Demo 2” is not a single test, but the overall performance of the manned dragon spacecraft from launch to recovery. Although the perfect launch of the spacecraft has been officially approved by NASA, there are still many risks on the way back from space.

it has two cone tube parachutes deployed at an altitude of 18000 feet, flying at a speed of about 350 miles per hour. When the ship is at an altitude of about 6000 feet, it can fly at a speed of 119 miles per hour, and then all four main parachutes will be deployed to slow down the final landing of the spacecraft.

in view of the possible deviation of the landing point caused by the landing angle of the spacecraft, the official landing sites are Pensacola, Tampa, Tallahassee, Panama City, Cape Canaveral, Daytona and Jacksonville.

six hours before the separation of the Dragon spacecraft from the international space station, SpaceX and NASA jointly decided that the preferred splash area for this time was Pensacola.

SpaceX staff have previously arrived at the seven landing sites and sent two rescue vessels “go searcher” and “go navigator” to search and rescue in the Gulf of Mexico and the Atlantic Ocean off the coast of Florida.

there are more than 40 spacecraft engineers from SpaceX and NASA, water recovery experts, medical professionals, spacecraft crew, NASA cargo experts and other personnel to assist in the recovery work.

Finally, the Dragon spaceship splashed into the Gulf of Mexico at 2:48 Beijing time on August 3. Two pilots said it was “very good at the moment.”.

two rescue boats carrying SpaceX personnel immediately evacuated from the main recovery vessel after the splash. The first ship is mainly responsible for checking the integrity of the capsule and testing for spontaneous combustion propellant vapor in the area around the Dragon spacecraft. Once cleared, the crew on board began to prepare for the salvage of the ship. The second clipper is responsible for recovering parachutes that have been detached from the capsule and are in the water.

at this time, the main recovery ship can enter and start to lift the crew cabin of the Dragon spaceship onto the main deck. Once the re-entry module enters the main recovery vessel, it is first moved to a stable position to open the hatch, wait for medical personnel to conduct preliminary examination, and assist benken and Hurley to leave the spacecraft.

the whole process lasted more than an hour from the splashing of the spaceship to the astronauts’ leaving the cabin. At 4:00 on August 3, Beijing time, the door of the Dragon spacecraft opened and two astronauts left the cabin.

after leaving the dragon capsule, Benton and Hurley will be sent to the medical area on board the recovery ship for preliminary assessment. This procedure is similar to the way astronauts aboard Soyuz return to earth.

after the initial medical examination, Benton and Hurley will immediately fly to Kennedy Space Center Hospital by helicopter to receive full medical services, and finally return to Johnson Space Center in Houston, Texas.

astronauts Ben Ken and Hurley give a thumbs up to the camera with a smile after the door of the Dragon spaceship enterprise opened. NASA

Meanwhile, the Dragon spacecraft will be sent back to SpaceX’s Dragon lair in Florida for inspection and treatment. The SpaceX team will evaluate the data and functional performance of the Dragon spacecraft during the test flight, so as to complete the certification of the flight system for NASA commercial crew and the international space station project.

SpaceX has proved to NASA that the manned dragon spacecraft is fully capable of being used as a conventional vehicle for transporting American astronauts to and from the earth and the international space station.

next, SpaceX will prepare for the upcoming formal mission – “crew-1”. SpaceX needs to obtain NASA’s official authorization and certification before the specific mission is executed.

if successful, the next official mission will be composed of commander Michael Hopkins, pilot Victor Glover and mission expert Shannon walker from NASA, and mission expert Koichi Noguchi from JAXA, a Japanese aerospace research and development agency.

the official mission, code named crew-1, will still depart from Launch Pad 39A at Kennedy Space Center. The four crew members are expected to stay at the international space station for six months.

at present, the official has not given the exact time for the next launch, because it will take about six weeks to complete the certification, which is initially expected to wait until the end of September at least.

51 years ago today, Apollo 11 splashed down and successfully returned from the moon. Today, 45 years ago, the Apollo Soyuz spacecraft splashed down, the last flight of the Apollo series.