NASA’s uncrewed Artemis 1 mission has started its return to Earth. Having reached the furthest distance on November 28th, the vehicle started back towards the Moon as it travels along its distant retrograde orbit (DRO). Along the way it completed a further series of flight tests of both its manoeuvring systems and flights systems, including Callisto, NASA’s voice recognition software (based on Amazon Alexa) designed to assist crews during flight operations.
On Wednesday, November 30th, the vehicle completed the first of three engine burns to start it on it way back to Earth. This was an “orbit maintenance burn” designed to maintain Orion’s trajectory as it headed back to the Moon, and to decrease its velocity, allowing the Moon’s gravity play a greater role in the craft’s trajectory. At 95 seconds, this burn ran for slightly longer than originally planned, allowing mission engineers gather additional data to characterise the impact of the vehicle’s thrusters and their radiative heating on the spacecraft’s solar array wings to help inform Orion’s operational constraints.
On Thursday, December 1st, Orion completed the more critical DRO exit burn, slowing it further and “bending” its trajectory so it make a close passage around the Moon, bringing it to 127 km above the lunar surface, a point it will reach on Monday, December 5th.. At this point Orion’s service module will fire its main engine to exit lunar orbit to move into a trans-Earth Injection (TEI) flight path that will see it reach Earth on December 11th, when it will enter the atmosphere for a splashdown in the Pacific Ocean.
As well as testing the flight system, NASA has used the flight back towards the Moon to capture further stunning images and video, with the agency also releasing a high-speed “mission highlights” video covering the mission’s launch and flight to the Moon and into DRO.
JWST and Keck Continue to Reveal Titan
In my previous Space Sunday update, I noted that the James Webb Space Telescope (JWST) has returned to full operations following the correction of an issue with its Mid-Infrared Instrument. The event was marked by the release of images captured by the instrument of Saturn’s largest moon, Titan.
Since then, NASA, the space Telescope Science institute and the Keck observatory have released further stunning images of the moon, these taken with JWST’s Near Infrared Camera (NIRCam).
In the first, two images of the moon are placed side-by-side captured using different filters. They reveal both the lower reaches of the moon’s methane-heavy atmosphere. The second reveals how NIRCam can look through the murk of such an atmosphere to see the surface of the moon. Both images reveal intriguing aspects of the moon.
On the first, NIRCam reveals two clouds, labelled “A” and “B”, whilst the second reveals some of the known surface details of the moon including Kraken Mare, believed to be a methane / hydrocarbon sea, and above which, intriguingly, “cloud A” had formed, suggesting it might be a weather system. Also imaged was Belet, a range of dark dunes and a bright albedo feature of uncertain nature, called Adiri.
The clouds were of particular interest because they can validate long-held predictions from computer models about Titan’s climate: that clouds would form readily in the mid-northern hemisphere during its late summertime when the surface is warmed by the Sun. Further, observing how the clouds move or change shape might reveal information about the air flow in Titan’s atmosphere.
To this end the JWST team observing Titan contacted colleagues at the Keck Observatory, Hawai’i who were about to start their own infra-red observations of Titan. They agreed to carry out a similar series of observations of the moon to allow for comparative science studies to be carried out.
The result is a series of images which appear to show the formation, movement and dissipation of the same cloud formations over the course of several days (November 4th-7th), offering the potential for those promised insights into climate and weather around Titan – although astronomers caution the clouds seen by Keck might be of different origin.
NIRCam isn’t the only JWST instrument which gathered data on Titan during the observation period. The Near-Infrared Spectrograph (NIRSpec) examined the light reflected by Titan’s atmosphere to gather its spectra, which will allow scientists map what compounds are present in the lower atmosphere — including a strange bright spot over the moon’s South Pole, which has been a source of puzzlement for astronomers and planetary scientists.
China Sets a National Record for Taikonauts in Orbit
China had six tiakonauts in orbit for the first time this week as the crew of Shenzhou 15 joined their colleagues of the Shenzhou 14 mission aboard the nation’s new space station of a handover of station operations.
Fei Junlong, Deng Qingming and Zhang Lu departed Earth on 29th November 2022 atop a Long March 2F rocket at around 15:08 UTC on November 29th. The vehicle docked with the forward docking port on Tiangong’s docking hub 6.5 hours later. Following the required post-docking checks, the hatches between station and vehicle were undogged and opened a 23:33 UTC, allowing the Shenzhou 14 crew welcome their colleagues onto the station.
The new crew will be aboard the station for 6 months, and after their welcome and a rest period, they joined Shenzhou 14 team is preparing the station for their stay, carrying out a range of small but essential maintenance work using equipment flown to the station aboard the Tianzhou 5 resupply mission in November.
With the hand-over work completed by Sunday December 4th, the Shenzhou 14 crew departed the station aboard their vehicle at 03:01 UTC. Once clear of the station, they performed a series of fast return de-orbit procedures, allowing them to soft-land within the Dongfeng landing area in the Gobi Desert in the Inner Mongolia Autonomous Region nine hours later at 12:00 noon UTC.
Their return marked the most successful crewed mission to date for China, with 180 days spent in orbit, three spacewalks, a space lecture and overseeing multiple tests of the station, the arrival of both the the station’s science modules, the manoeuvring (and eventual undocking) of the Tinazhou 4 automated resupply vehicle and the arrival of Tianzhou 5.
The Shenzhou 15 crew are liable to be even busier. Among their tasks, they will be expected to carry out or monitor over 100 experiments both within the science modules and outside, across the six months of their stay. They will also be carrying out three or four EVAs (spacewalks) which will bring new challenges, including “parallel operations” each taikonaut outside the station working independently to the other, with the crew member aboard the station balancing the needs of both EVA crew. Then are scheduled to return to Earth in May 2023.
SpaceX Starship Update
On November 29th, SpaceX completed a second static fire test on its Super Heavy Booster 7, the booster earmarked to try to carry one of the company’s Staship vehicles to orbit – and once again things did not go as quite as planned.
Lasting 13 seconds, the test was 3 seconds longer that the first static fire test, performed on November 14th, although it involved three fewer engines: 11 compared to the 14 used in the November 14th test. However, like the first test the firing resulted in damage to the orbital launch facility, gouging clunks of concrete from under the base of the launch table, hurling them into the air where they might strike the vehicle or the launch facilities.
As I noted following the November 14th test, the flying debris is the result of both an insufficient sound suppression system (SSS) and provision of a flame deflector. The former is best known for deluging a rocket launch platform with thousands of litres of water in order to absorb the sound of the rocket engines which might otherwise be deflected up against the rocket to damage it. However, it has an additional function: to “drown” the launch platform and the area beneath it to protect them from the searing blast of the engine exhausts at lift-off.
The flame deflector performs a similar role in protecting launch facilities from rocket engines by deflecting the exhaust plumes out and away from the launch stand (and also carrying the excess water (and steam) from the SSS away from both the platform and rocket, further lessening the risk of damage to either. Part of the sound suppression system used by NASA for Space Launch System rockets is shown being tested in the video below. This element protect the concrete base on the launch facility, with water also being directed down the central flame deflector seen within the trench used to channel heat, steam and sound away from the launch platform. A second suppression system (not seen in this video) is built-in to the mobile launch platform itself, to give it the aforementioned protection from the heat of the SLS four main engines and two SRBs at launch.
However, SpaceX has thus far eschewed and flame deflector and has opted for a spray system of water and nitrogen gas delivered through pipes within the circular launch table on which the super Heavy / Starship combination sits. Already upgraded since its initial installation, this system appears adequate in terms of sound suppression, but does not properly protect the concrete apron directly below the rocket engines from their full fury.
Whether this remains the case with all Starship / Super Heavy launch facilities remains to be seen: this first orbital launch facility is very much a prototype. However, the lack of consideration for any form of flame deflection mirrors a similar decision not to initially equip the launch stand with another basic requirement of a launch facility: burn-off igniters which resulted in the July 11, 2022 spin-start test explosion under Booster 7.
Following the November 29th test, two of the booster’s Raptor engines were swapped out at the pad, although it is unclear whether his was the result of damage from the materials flung upwards and outwards from the apron during the test or as a result off other motor issues. After this work had been completed, Booster 7 was disconnected from the launch platform and returned to the production area. This may again be to allow further damage inspections to be carried out, by is likely equally to allow the rest of the booster’s aft skirt to be fitted.
At the same time as Booster 7 has been under test, Ship 24, which is due to be mated to it for the launch attempt, has been undergoing repairs at the sub-orbital launch platform where it has been completing its own series of static fire tests. The results of these tests appear to have been fed back into the assembly of Ships 25 and 26, the next vehicles in the series.
SpaceX has indicated they are still planning a further 20-sec 33-engine Raptor static fire test prior to any launch attempt, which will also include a further autogenous repressurisation test (feeding cooled gasses from the engines back up into the propellant tanks to maintain their pressure as their contents are used). This coupled with the fact that the Federal Aviation Administration has yet to issue a launch license, means that the launch attempt is unlikely to come before 2023.