CHANG'E-5 LANDING SITE CHOSEN
Top video: the Chang'e-5 lunar probe will be launched by a Long March-5 carrier rocket to collect samples from the Moon and bring them back to Earth. Chang'e-5 is scheduled to enter the launch site in August 2019, preparing for its launch by Long March-5 around November 2019. Credit: SciNews
THE CHANG'E-4 WILL BE A LANDER/ROVER'S MISSION
THE CHINESE CHANG'E-5 MISSION WILL RETURN SAMPLES FROM THE MOON
Since the Apollo's missions, China will be the first to return to Earth, samples from the near side of the Moon. That will be the mission of Chang'e-5, scheduled for November 2019, near Mons Rümker in Oceanus Procellarum, a large area of lunar mare in the northwest region of the Moon.
Scientists work on China's Chang'e-5 landing and ascent vehicles. Credit: Framegrab/CCTV
Chang’e-5 is China’s first lunar sample return mission and the most ambitious endeavor in the country’s lunar program, aiming to introduce new technologies and techniques such as a fully-automated rendezvous in lunar orbit and sample transfers in between different spacecraft modules.
The spacecraft includes 4 modules such as a Service Module, a Return Vehicle, the Lander and the Ascent vehicles, for a mass around 8 metric tons. With this weight, it will need a powerful launch vehicle like the Long March 5 rocket, which can deliver the craft to a direct trajectory to the Moon.
The Chang'e-5 Lander has an identical structure to that of the Chang'e-3 with a dry mass of over 1 metric ton and a fueled mass of up to 3,800 kg. And, to reduce the length of the Service Module, the Return Vehicle (RV) is installed in its cavity.
The Long March 5 rocket
The Service Module (SM) is equipped with power-generating solar arrays, communication systems for command uplink from Earth and telemetry downlink as well as a propulsion system and attitude control thrusters.
Based on the propulsion technology used on the Chang'e-3, the vehicle will use hypergolic propellants. This propulsion system will be used for trajectory correction maneuvers on the way to the Moon, the lunar orbit insertion burn, the orbital maintenance and the trans-Earth injection burn at the end of the mission. In fact, Chang’e-5 stack will complete a complex mission that consists of 11 different phases and spacecraft configurations to set up the appropriate conditions for lunar orbit insertion 5 days after launch.
When the craft reaches an altitude of 200 km, likely a polar orbit, the Lander – Ascent Vehicle stack will separate from the SM using pyrotechnics. The Lander will use its propulsion system to lower the periapsis 15 km ahead of landing with the periselene location carefully positioned to line up with the landing site.
The Lander will make one continuous landing burn using its main engine that actively throttles down as part of the descent. The 700-second landing sequence begins with a deceleration taking the vehicle from an altitude of 15 to 2 km transitioning to a quick Adjusting Sequence to move from a horizontal flight to a vertical descent.
Landing will take place at the beginning of a Lunar Day (14 Earth days in duration).
Coarse obstacle avoidance is completed before horizontal velocity is eliminated, setting up for a Hover Segment at 100 m for image acquisition and fine-obstacle avoidance followed by a constant-velocity descent. At an altitude of 4 m, the Lander will shut down its engine and drop to the surface.
Power is delivered by 2 solar arrays that can be opened and closed on command. Navigation will be provided by an inertial guidance platform, a laser ranging system, an altimeter ,and an optical descent camera.
According to information published in Chinese papers, Chang’e-5 will use a four-degree of freedom robotic arm for the acquisition of regolith samples and small rocks to be delivered to the Ascent Unit.
The end-effector of the arm includes a scoop for the acquisition of samples, a sample processing system using vibration and separation mechanisms that ensure that several individual samples can be acquired without coming in contact with one another. The entire end-effector containing the samples can be separated from the arm for the transfer to the Ascent Vehicle.
Additionally, the lander includes a coring drill and penetrating mechanism that will acquire one or more drill samples in the form of an intact core up to a depth of 2 m making use of a rotary-percussive drilling mechanism. The drill core is delivered to the Ascent Vehicle inside a Kevlar tube that provides sufficient stability to protect the core while being flexible enough to be compacted in size for transfer to the Ascent Vehicle.
The Ascent Vehicle (AS) on the lander's top deck uses structural attachments to remain in place during orbital flight, landing and the surface mission. A central interface from the lander to the AS is attached at the top of the vehicle using an arm that can be moved to the side to clear the way for the vehicle to launch from the top deck of the lander.
For the flight to the Moon and the surface mission, the 2 solar panels will be kept in a stowed configuration, helped by electrical and data interfaces. This latter conception will also facilitate the sample transfer mechanism.
It is likely that the mission's goal is to complete all sampling and drilling operations within 1 lunar day to avoid hardware damage as a result of the harsh temperatures of lunar nights. After sampling and transfers of up to 2 kg of lunar material to the AS, all preparations for the return journey will be done.
The Ascent Vehicle will then use its propulsion system to go from an orbit of 15 km to one of around 180. Once this orbit is reached, the AS will dock in a fully-autonomous manner with the Service Module – Return Vehicle stack.
Sample transfers to the Return Vehicle will take place in lunar orbit. Once the transfers are completed, the Ascent Unit detaches for a free flight in lunar orbit ofat least 10 days.
The Chang'e-5 lander will set down near Mons Rümker in Oceanus Procellarum, a large area of lunar mare in the northwest region of the Moon. The lander, 1 of 4 units making up the Chang'e-5 probe, will then collect around 2 kg of samples of lunar regolith and rock from a depth of up to 2 min preparation for thereturn to Earth.
HISTORICAL CHINESE'S MISSIONS TO THE MOON
The Orbiter Chang'e-1 (was like the Chang'e-2)
Chang'e-2, a robotic spacecraft built and operated by the Chinese National Space Administration (CNSA), recently left lunar orbit, and moved on to a new leg of its mission. The probe is now...
The Lander Chang'e-3
The main propulsion system is built around a central main engine, which is fired to lift off from the lunar surface.
To docks, the AV uses a claw-type mechanism. On the active side, three claws, spaced by 120°, close when they comes in contact with the passive side of the system. This mechanism includes struts that are grasped by claws to create a firm bond between the AS and the RV. At this moment, samples are transferred to the RV, which uses a robotic system.
When transfers are complete, the Ascent Unit is separated so that the Service Module can boost the vehicle out of orbit and carrying the Return Vehicle back to Earth.
The Chang'e-5 Return capsule (right) and Lander and Ascend Vehicle (background), undergoing tests. Credit: Framegrab/CCTV
The Service Module will then conduct the trans-Earth insertion for a five-day flight back to Earth. At 5,000 km from Earth, the Return Vehicle will separate from the SM for the final 20 minutes re-entry.
To re-entering at a speed up to 11 km/s, the Return Vehicle will utilize a Skip Re-Entry to increases the range, to reduces the overall G-load and the thermal stress on the heat shield.
A Skip Re-Entry is done by an initial dip into the atmosphere, which reduce the velocity of the spacecraft. At this moment, it perform a pull-up maneuver, again from the atmosphere and continue on a ballistic sub-orbital trajectory. This maneuver lead to a new entry at a reduced speed for the descent and a parachute-assisted landing on Earth's surface.
Credits: Andrew Jones, https://gbtimes.com/china-confirms-landing-site-change-5-moon-sample-return /