Chang'e 5 Test Mission Updates - SPACEFLIGHT101
October 31, 2014
China successfully demonstrated its Chang'e 5 lunar Return Vehicle on Friday when the craft made a successful re-entry and an on-target landing in the Inner Mongolia region at 22:42 UTC, concluding an eight-day circumlunar flight to set up for Friday's entry demonstration. Official Chinese media confirmed that the landing was a success.
The Chang'e 5 Test Mission had the primary goal of testing a lunar Return Vehicle in an operational environment by demonstrating a complex skip re-entry at a velocity that will be encountered when returning from the Moon. The spacecraft consisted of a Service Module, based on a design flown on the Chang'e 1 and 2 lunar orbiter missions, and an operational Return Vehicle to be used for Chang'e 5 that will become China's first attempt to return samples from the Moon.
Setting out to complete an ambitious pathfinder mission for future robotic sample return missions to the Moon, the Chang'e 5 Test Vehicle launched atop a Long March 3C/E rocket back on Thursday, October 23.
Photo: Xinhua
Entering a lunar free return trajectory, the spacecraft completed two course correction maneuvers during its four-day outbound leg to begin targeting the proper re-entry location for an on-target landing.
Photo: CASC/CCTV
On Monday, the craft entered the Moon's gravitational sphere of influence and made its closest approach up to a distance of 12,000 Kilometers, collecting a series of images using cameras installed to monitor the deployment of the craft's solar arrays earlier in the mission. The stunning photos include shots of Earth, the lunar surface and both, Earth and Moon, in the same frame.
With its flyby complete, the Chang'e 5 Test Vehicle was inbound again - set for another four-day leg of its journey to get back to Earth at a precisely timed moment to begin its re-entry at the appropriate location. A set of up to three Trajectory Correction Maneuvers were available to the craft to fine-tune its course back to Earth, but only one of the maneuvers was needed.
All eyes were on the big screens at the Mission Control Center in Beijing when the craft reached a distance of 5,000 Kilometers to Earth. At 21:53 UTC, the Service Module and Return Vehicle parted ways, being separated after the Service Module provided power and command/telemetry relay to the smaller Return Vehicle throughout the flight around the Moon.
Following separation, the Return Vehicle was on a path taking it into Earth's atmosphere within about 19 minutes time. The Service Module on the other hand was planned to re-orient and fire its 490-Newton main engine three minutes after separation to alter its trajectory in a way that avoids re-entry to set the spacecraft up for a secondary mission within the Earth-Moon system. It was not confirmed whether the Service Module achieved this maneuver and details on the secondary mission of the vehicle were also not given.
Photo: CCTV via 9ifly.cn
Photo: CCTV via 9ifly.cn
The Return Vehicle started its re-entry about 20 minutes after module separation, hitting the atmosphere with a speed of 11 Kilometers per second, a record for the Chinese. To reduce the peak temperature and heating rate on the Return Vehicle, an entry design was devised around the skip re-entry technique that was used with mixed success by the Russian Zond missions in the 60s & 70s and was also conceptualized for the Apollo missions that ended up using a modified entry scheme.
In the final minutes of its flight, the Chang'e return vehicle used its own hydrazine-powered attitude control thrusters to enter an orientation with its heat shield pointing forward and its center of gravity in a full lift-down position to ensure a good initial capture when entering the atmosphere. The vehicle performed an initial dip into Earth's dense atmosphere up to a point 60 Kilometers in altitude before conducting a pull-up maneuver to enter a path taking it out of the atmosphere again.
The exit conditions had to be controlled precisely to ensure the craft reached the proper sub-orbital velocity and flight path to be able to make its second re-entry at the planned location. Overall, the mission only had an entry corridor of 0.2 degrees.
Once out of the atmosphere, the craft could no longer use aerodynamic control, passively coasting up to an apogee altitude of 140 km. From there, the craft again dropped and entered the atmosphere at 22:22 UTC. Performing re-entry in two phases leads to a reduction in peak heating rate, thus reducing stress on the heat shield that had to dissipate a little over two times the energy seen during a re-entry from Low Earth Orbit.
The second re-entry saw the vehicle using its guidance system to modify its lift to target a landing site in the Inner Mongolia region. Around 22:32 UTC when passing ten Kilometers in altitude, the Return Vehicle deployed its parachute to slow down from subsonic velocity to a safe landing speed, also transitioning from horizontal to vertical flight.
The Chinese tracked the entire approach, entry and landing process starting with ground stations in Africa that monitored the initial dip into the atmosphere occurring just off the east coast of the Kenya/Somalia region. The Yuanwang 3 tracking ship took station in the Arabian Sea to monitor the initial entry and the exospheric skip before ground stations in Pakistan and China tracked the vehicle.
With the craft coming in right on its path, infrared cameras were used to monitor the vehicle's progress toward its landing site.
Image: NASA
Photo: CCTV via 9ifly.cn
Photo: CCTV via 9ifly.cn
At 22:42 UTC, the Chang'e Return Vehicle touched down in the target location in Siziwang Banner of China's Inner Mongolia Autonomous Region. Prior to landing, a 115 by 190-Kilometer box was identified in a navigational warning to be the primary landing site of the mission.
Photo: Xinhua
Photo: Xinhua
Following landing, recovery forces raced to the vehicle in helicopters and arrived within a few minutes, indicating that the landing was very close to the bulls-eye target.
Returning inside the capsule is precious cargo consisting of a variety of samples that made the journey from Earth to the Moon and back to allow scientists to study the effect of the deep space environment on organisms, seeds, plants and other samples.
Opportunities of flying samples beyond Earth orbit have been extremely rare over the past decades and this mission offered a great opportunity to fly a sizable sample payload of several Kilograms.
The success of the Chang'e 5 Test Mission will pave the way for China's first lunar sample return mission as early as 2017 with a second mission following by 2020. These will be the first lunar sample return missions since 1976.
The sample return missions will be of a very complex nature featuring a spacecraft weighing eight metric tons and consisting of four modules.
The mission would include new technologies to realize a flight into orbit around the Moon, a propulsive landing on the lunar surface, the robotic acquisition of samples, a propulsive return to orbit of a sample-carrying ascent vehicle, a fully autonomous rendezvous in lunar orbit, the exchange of sample material between spacecraft modules and the successful return of the sample material.
Prior to flying the Chang'e 5 mission China is expected to launch the Chang'e 4 spacecraft which will be another lander and rover, following in the footsteps of
Chang'e 3. It is likely that this mission would include more demonstrations of equipment to be used for lunar sample acquisition in an overall effort to reduce the risk of the lunar sample return mission which can be considered to be China's most ambitious robotic space mission.