Space Sunday: Mars, Starship and a meteor that flattened a city

September 10th, 2021: after successfully gather two samples from the rock dubbed “Rochette” (seen in the foreground, the bore holes clearly visible), the Mars 2020 rover Perseverance paused for a “selfie” using the WATSON imager mounted on the robot arm turret. Credit: NASA/JPL

It’s getting interesting on Mars. Jezero Crater, the home of the Mars 2020 mission is going through a change in seasons, bringing with it a drop in atmospheric density that is proving challenging for the Ingenuity helicopter, which recently completed its 13th flight.

The little drone was designed to fly in an atmosphere density around 1.2-1.5% that of Earth, but with the seasonal change, the average afternoon atmospheric density within the crater – the afternoon being the most stable period of the day for Ingenuity to take flight – has now dropped to around 1% that of Earth. This potentially leaves the helicopter unable to generate enough lift through its rotors to remain airborne.

The solution for this is to increase the rate of spin within rotors to something in excess of their nominal speed of around 2,500-2,550 rpm. However, this is not without risk: higher rpm runs the risk of a significant increase in vibrations through the helicopter that could adversely affect its science and flight systems. Also, depending on the wind, it could result in the propeller blades exceeding 80% of the Martian speed of sound. Sound this happen, the rotor would pick up enough drag to counter their ability to generate lift, leading to a mid-flight stall and crash.

To better evaluate handling and flight characteristics, therefore, the flight team are going back to basics an re-treading the steps taken to prepare Ingenuity for flight. This will see the propellers spun to 2,800 rpm with the helicopter remaining on the ground. Data gathered from this test will be used to make an initial assessment of blade speed required to get Ingenuity off the ground – believed to be somewhere between 2,700 and 2,800 rpm, and make an initial assessment of vibration passing through the helicopter’s frame. After this, it is planned to carry out a very simple flight: rise to no more than 5 metres, translate to horizontal flight for no more that a few metres, then land. Data from this flight – if successful – will then be used in an attempt to determine the best operating parameters for Ingenuity going forward.

The power of Perseverance’s camera: The lower image shows a true colour view of a feature dubbed “Delta Scarp”, captured by the rover’s MastCam Z system from a distance of 2.25 km. The upper picture shows details of the feature, as captured from the same distance, using the rover’s SuperCam instrument.. Credit: NASA/JPL

In the meantime, the Perseverance rover is continuing its work. Following the successful gathering of its first ample, the rover has been further revealing the power of its imaging systems, Mastcam Z and SuperCam, the two camera system mounted on its main mast.

Designed for different tasks, the two systems nevertheless work well together to provide contextual and up-close images of features the rover spies from distances in excess of 2 km away, allowing science teams to carry out detailed assessments before sending the rover to take a closer look. Also, in the wake of the sample gather exercise at the rock dubbed “Rochette”, NASA have provided a general introduction to two more of the rover’s instruments, which are mounted on the turret at the end of the rover’s robot arm. Catch the video below for more.

At the same time, and half a world away, the InSight mission Lander, despite suffering a severe degrading of its power capabilities as dust continues to accumulate on its circular solar arrays, has detected a  powerful Marsquake less than a month after detecting two equally powerful quakes originating at two different point under the planet’s surface.

All three were the latest in a long like of Marsquakes – also called “tumblors” – that have revealed much about the planet’s interior in the almost three years since InSight placed its seismometer on the planet’s surface, including the fact its core is larger than had been believed. The vast majority of the tumblors thus far detected have originated in the  Cerberus Fossae region of Mars, some 1,600 km from the lander. However, on August 25th, a quake measuring 4.1 magnitude was recorded with an epicentre just 925 km from the lander whilst marking it as the most powerful tremblor Insight had recorded (the previous record holder measure 3.7 – five times less powerful).

Captured in July 2021, this image shows InSight’s Seismic Experiment for Interior Structure (SEIS) instrument dome on the surface of Mars. This is the instrument that has been recording tremblors on Mars. Credit: NASA/JPL

But then on the same day, a second quake was detected, hitting 4.2 magnitude, marking it particularly powerful, given its epicentre was calculated to be 8,600 km from the lander, and possibly focused within Vallis Marineris, the “Grand Canyon of Mars. This was matched on September 18th by a further 4.2 magnitude quake – epicentre currently unknown. But what made this tremblor remarkable was its duration – almost 90 minutes! (By comparison, the longest recorded duration of an quake on Earth is under 5 minutes.) Exactly why and how such an event should or could last so long is unknown, and has the InSight science teams scratching their heads.

Did a Cosmic Event Give Rise to the Biblical Legend of Sodom and Gomorrah?

Tall el-Hammam was – up until 3,600 years ago – a thriving centre of life and commerce for an estimated 8,000 people. Located close to the Dead Sea in what is now modern day Jordan, the valley it occupied lay some  22 km west of the city of Jericho and was one of the most productive agricultural lands in the region before being practically deserted for some 500-700 years, the soil inundated with salts to the extent nothing would grow.

The location of the city has been subject to archaeological study since 2005, and researchers there have been struck by the curious nature of what little remains of the city: foundations with melted mud brick fragments, melted pottery, ash, charcoal, charred seeds, and burned textiles, all intermixed with pulverised mud brick and minerals that can only be produced under extremes of temperature and / or pressure. The more the city’s ruins were uncovered, the more the evidence pointed to some terrible calamity having befallen Tall el-Hammam and its surroundings, prompting the archaeologists to call in experts from the field of astronomy, geology, and physics. Their research has lead to the conclusion that the city was practically at the epicentre of a “cosmic airburst”.

Moment of detonation: an artist’s (rather mild) interpretation of the moment a 50m diameter chunk of rock travelling at 61,000 km/h detonated in the skies above Tall el-Hammam, Jordan, 3,600 years ago in a 15 megaton blast that obliterated the city in seconds. Credit: Allen West and Jennifer Rice, CC BY-ND

In short, 3,600 years ago, a piece of rock probably 50 metres across slammed into the atmosphere at 61,000 km/h. It survived the initial entry and fell to an altitude of approximately 4km above Tall el-Hammam before air resistance finally overcame its integrity. The result was a  15 megaton explosion that instant drove air temperatures to around 2,000ºC, enough to instantly flash-burn textiles, wood and flesh, and melt everything from swords and bronze tools to pottery and mud brick.

Seconds later, the shockwave from the explosion struck the city. Travelling at 1,200 km/h, it utterly pulverised what was not already aflame. Roughly a minute after the explosion, that same shockwave rolled over the city of Jericho, probably demolishing a good portion of its defensive wall and the buildings within it. That same shockwave also impacted the Dead Sea, potentially lifting vast amounts of salt water into the air, which rained back down over the valley, rendering it infertile for the next few hundred years, until rainfall could wash the salts out of the top soils.

The evidence for the cataclysm comes in multiple forms, from the melted pottery and mud brick through the clear evidence the city was pulverised in a manner that left a clearly defined “destruction layer” within the ruins, to the fact that within those ruins are deposits of shocked quartz, which are only formed when grains of sand are compressed with of force of 725,000 psi, and microscopic diamondoids, produced when carbon materials (e.g. plants, wood, etc.), are simultaneously exposed to massive extremes of temperature and pressure, and are a hallmark of ancient impact sites around the world.

A satellite image of the Middle East, showing the location of Tall el-Hammam on the northern coastal area of the Dead Sea. Satellite image via NASA

The ruins bring home the very real risk posed by near-Earth objects as they zap around the Sun, crossing and re-crossing Earth’s orbit. That a cosmic object also brought about the destruction of a small city and its 8,00 inhabitants raises the question of whether someone witnessed the event (obviously from many kilometres away) or its aftermath, and the telling and re-telling of the tale of destruction eventually morphed into the Biblical tale Sodom and Gomorrah, the two “cities of the plains” of the Dead Sea (and therefore potentially close to the site of Tall el-Hammam), supposedly destroyed by God in a rain of fire and rock falling from the sky.

SpaceX  Update

The Federal Aviation Administration (FAA) issued its long-awaiting Draft Programmatic Environmental Assessment (PEA) related to Starship / Super Heavy operations out of the SpaceX Starbase facilities in Boca Chica, Texas.

Overall, the report indicates there are few impediments blocking SpaceX from being able to undertake Starship / Super Heavy launches from the facilities, with most concerns already being mitigated. One one significant issue has been left outstanding: the impact launch operations may have on the numerous species within the Boca Chica locale that are recognised by the Federal Endangered Species Act; a issues that requires further investigation by the U.S. Fish and Wildlife Service.

The outcome of this investigation, together with the feedback from the period of public review that runs through until October 18th, will form part of the final PEA, which will either give SpaceX the OK to continue their work (and go towards the FAA potentially granting the company a licence for Super Heavy / Starship launches, or  – if significant issues are found to remain – trigger a much broader Environmental Impact Study  (EIS) be undertaken, which could further delay the programme – although at this stage, this seems unlikely.

What is particularly interesting about the report is it indicates that SpaceX has committed to no more that 5 “operational” launches of Starship / Super Heavy per year; any attempt to exceed this will require a further PEA study or even a full EIS, and the granting of new FAA licence extensions.

A table from the FAA PEA for SpaceX Super Heavy / Starship operations out of Boca Chica, showing the annual cadence of development and operational launches covered by the report. Credit: FAA / SpaceX
Given that in time the company plans to operate “hundreds” of Starship launches, with turn-around times measured in “hours”, this suggests that, overall, Starbase will only play a limited role in SpaceX’s Starship aspirations, and that the greater emphasis will fall on other launch options, such as the in-developing floating launch platforms Phobos and Deimos, and facilities such as Launch Complex 39A at Kennedy Space Centre (where work on Super Heavy launch facilities are currently on hold), and other still-to-be-announced launch facilities.

In the short-term, the cadence – which also doesn’t account for flights required to develop a reliable recovery of vehicles, both a separate and related development track  – may give Blue Origin additional ammunition for their case against NASA, depending on how many additional launch facilities SpaceX can implement ahead of NASA’s planned returned to the Moon. This is because SpaceX currently has the sole contact to supply NASA with a Human Landing System (HLS) – the vehicle that will transport cargo to lunar orbit and cargo and crews from lunar obit to the surface of the Moon and back. However, the Starship HLS will required around 8 or 9 Super Heavy launches just to send a single HLS vehicle and its cargo to the Moon, and multiple flights on a periodic basis to refuel the vehicle to allow it to make repeated flights between lunar orbit and the Moon. These operations will clearly require multiple launch facilities and time to develop the necessary on-orbit refuelling capabilities (which won’t happen overnight), so Blue Origin might argue that relying solely on SpaceX to develop their vehicle and all the required infrastructure needed to handle its unique launch characteristics by 2025 is a further demonstration of a serious error on NASA’s part.

Pictured on September 20th, the nose area of Starship 20 is now devoid of markers indicating heat shield tiles that need replacing or re-aligning. Credit: What About It

In the meantime, SpaceX continues to move ahead with preparations for their first orbital launch attempt from Boca Chica. Most recently, the cryogenic tanks that will eventually feed propellants and inert liquid helium and nitrogen to vehicles on the launch mount have started cryogenic load testing ahead of the tank farm itself being finished. In addition, work on refurbishing Starship 20’s heat tiles is almost entirely completed. This weekend saw the final major element added to the Quick Disconnect (QD) arm, and Booster 4 was been removed from the orbital launch mount to eliminate the risk of damage during the installation of the massive “chopstick” arms that will eventually be used to try and “catch” returning Super Heavy boosters and Starship vehicles.

In Brief

Starliner Launch Delay to 2022 Now “Likely”

In August 2021, I covered the return of the latest Boeing CST-100 Starliner capsule to the Boeing factory after the second attempt to complete an uncrewed demonstration flight to the International Space Station (ISS) had to be postponed on August 13th, 2021.

It was an embarrassing moment for Boeing, who are responsible for developing the more expensive of the two US “taxis” designed to transport crews to / from the ISS, coming after more than 18 months of re-working the capsule’s systems and processes following an incomplete demonstration flight in December 2019. The route cause of the postponement were a handful of stuck thruster valves, and a factory-based assessment is leaning towards completely removing the valves for a thorough inspection. This means that, given the current launch schedule for the ISS, which will see a number of “private” flights to it, Starliner is unlikely to be able to get to the ISS  until early 2022.

China Launches Tianzhou 3; Female Taikonaut Slated for Shenzhou 13

Monday, September 20th, 2021, saw the launch of China’s Tianzhou 3 automated cargo spacecraft Wenchang Launch Centre atop a Long March 7 rocket on a “fast track” trajectory to join the Tianhe 1 core module of China’s new space station. The resupply vehicle, carrying around 6 tonnes of equipment and consumables performed a fully automated rendezvous and docking with Tianhe 1 seven hours after launch.

A Long March 7 lifts-off on September 20th, carrying Tianzhou 3 up to the Tianhe 1 core module of the Chinese space station. Credit: CCTV

It arrival now leaves the way clear for the next crew mission to the nascent space station, Shenzhou 13, which is expected to lift-off with its Long March 2F launch vehicle from Jiuquan in the Gobi Desert in early October. While the crew has not been confirmed, it is believed it will include one of China’s two women taikonauts,

Wang Yaping, who flew aboard the Shenzhou 10 mission to the Tiangong-1 orbital laboratory in 2013, and has been in training for space station missions. Shenzhou 13 will remain at the station – which currently comprises the Tianhe 1 core  module, plus the Tianzhou 2 and 3 re-supply vehicles – for some 6 months, the crew carrying out assorted verification checks on Tianhe 1 and its capabilities, including using the robot arm to manually manipulate the Tianzhou 2 vehicle.

Wang Yaping, training for her flight on Shenzhou 10 in 2013, is one of only three women accepted into the ranks of China’s tiakonauts, and only one of two to have flown into space. Credit: Reuters

China had indicated that 2022 should see the Tianzhou 4 resupply vehicle dock with Tianhe 1 in April, after the return of Shenzhou 13 and the de-orbiting of Tianzhou 2 and 3. The crew flight of Shenzhou 14 will then launch in May 2022, and will oversee the arrival of the two science modules for the station – Wentian (to launch in May-June 2022) and  Mengtian (August-September 2022). In addition, China has suggested the space station could be expanded with a further 3 modules starting in 2023.

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