Space Sunday: starships, helicopters and rockets

A camera close to the landing zone captures Starship SN15 with two good Raptor motor burns bringing it into a safe landing on May 5th. Credit: SpaceX

SpaceX has achieved its first successful landing of a Starship prototype after Starship SN15 was launched on May 5th, 2021.

The vehicle was the fifth full-scale prototype of the vehicle SpaceX intends to use on missions to Mars – and so much more – with the previous four, prototypes SN8, SN9, SN10 and SN11 all having suffered failures of various descriptions: SN8 came in too “hot” blowing up as it hit the landing pad; SN9 encountered motor issues that lead to being unable to remain upright so it also crashed into the landing pad; SN10 actually made a touch-down, but issues with one of its motors meant it blew up shortly afterwards; and SN11 exploded prior to landing after encountering issues when re-starting its Raptor motors.

Just before launch, Starship SN15 on the launch stand, venting excess vapours. The structure to the left is a test rig that is being used to simulate the dynamic stresses the forward section of an unladen Starship will face during atmospheric entry. Credit: SpaceX

SN15, however, is a substantially different vehicle to those. As the first of the “next generation” prototypes, it includes multiple updates and improvements throughout – including flying with the very latest iteration of the Raptor motors. Proof of this came in the run-up to the flight, when SN15 completing all its pre-flight tests without a significant issue – unlike the earlier models.

The vehicle lifted-off at 23:24 UTC, rapidly vanishing into low-altitude cloud as it climbed to the expected altitude of 10 kilometres, where it flipped into a horizontal skydiving descent. Just over 6 minutes after lift-off, the roar of the three Raptor engines re-starting reverberated through the clouds before the vehicle re-appeared in a tail-fist descent on  two of the three engines to complete a successful landing.

Starship SN15 on the landing pad, post-flight. The fire around the engine skirt is visible, and the fire suppression system can be seen dousing the area in water. Credit: SpaceX

Following landing, a small fire was visible at the base of the vehicle – the result of excess methane venting, and an issue SpaceX will need to address. However, it was clear that SN15 was safely down on the ground and “safing” procedures could commence.

Despite the atmospheric conditions, the team at team (this is not an official NASA group) had a number of video cameras placed around the SpaceX facilities at Boca Chica, Texas, and following the flight, they edited the footage from those cameras together to show the lift-off and landing sequences from different angles, some with the audio delay created by the distance of the camera from the launch stand edited out.

Some of these clips bring home the raw power of the Raptor engines – seconds after ignition, the shockwave of sound from the three engines on the Starship starts the camera vibrating – a small demonstration of what is to come when a Super Heavy / Starship combination lifts-off with no fewer than 28 of these engines firing simultaneously.

Following the flight, some pundits were forecasting SN15 could be set to make a second flight, possibly in short order – an idea fuelled be Elon Musk. This seems unlikely, as SpaceX will doubtless want to carefully examine the vehicle to learn all that they can from it prior to attempting to fly it a second time – if, indeed, they do.

All six of SN15’s landing legs suffered severe damage, as shown in this image, possibly the result of lateral loads placed on the vehicle on landing. Credit: SpaceX

As it is, the the landing legs – and possibly the base of the vehicle as well – suffered considerable damage during the “nominal” landing, as the image to the right shows.

Thought to be the result of lateral loading – the vehicle may have skidded sideways on touch-down – the damage is further evidence that SpaceX needs to seriously re-think how landing legs are mounted and deployed.

This is something the company his indicated it would be doing – and images of the proposed Starship Human Landing System (HLS) points to the direction in which they may move – although Musk has also floated the idea of eventually discarding any landing legs, and “catching” returning Starships via a launch tower, a-la his idea for Super Heavy – an idea that will presumably only apply to those Starships intended to operate no further than Earth orbit.

The next vehicle in the fleet that is likely to fly will be SN16, The legs on SN15 are the same as those on the earlier SN8-SN11 vehicles, and they are slated to be replaced by a more robust system,  and the degree of damage they suffered either as a result of a heavier touch-down or a possible lateral load being placed on the legs as a result of the vehicle “sliding” as it touched down. Either way, this damage along means that SN15 is unlikely to re-fly soon (although that doesn’t mean it won’t re-fly at some point).

As it stands, SN16 is now fully stacked and ready for transfer to a launch stand in order to have its Raptor engines fitted in preparation for a flight – this transfer could take place as soon as the coming week.

It is unclear how many more Starship launches will occur in the short-term: SpaceX is attempting to carry out an orbital launch of a Super Heavy Booster and an unladen Starship in July. Given the state of preparations – the company has yet to produce a fully flight-ready Super Heavy (Booster Number 1 has been scrapped, and work appears to have ceased on BN2 and BN2.1, leaving only BN3 under assembly at the moment), plus the orbital launch facilities are still under construction. Thus, unless attention and resources are significantly further shifted to booster development and testing, that July date seems to be highly ambitious.

Ingenuity Says ‘Farewell’ to “Wright Brothers Field”

On  Friday, May 7th, 2021, the Mars helicopter drone Ingenuity completed its 5th of five pre-planned test flights. In doing so, the little 1.8 Kg helicopter both set a new record and commenced a new phase in its mission.

During this flight, Ingenuity initially rose to the “usual” altitude of 5 metres, then said “farewell” to its operational based of “Wright Brother’s Field”, and headed south for a distance of  129 metres before coming to a hover. It this ascended further – climbing to 10 metres to take high-resolution of the area around itself, before descending to a landing in a flight lasting a total of 108 seconds.

The new landing site was selected on the strength of images gathered during the 4th flight for Ingenuity. It lies fairly close to the path the Mars 2020 Perseverance rover will follow as it now commences its science operations in earnest. The initial plans for the rover do not require it to make long-haul drives, but rather investigate the area to the south of the mission’s landing site, and this will allow the Ingenuity team to carry out further flights that can both further test their vehicle and allow them to potentially assist the rover team by scouting possible places of interest for the rover to explore.

Overall, Ingenuity is in fair better shape than had been expected at this point in its flight regime: the solar collectors are working optimally, the battery system is providing more than enough energy to both power the little vehicle and to keep it warm during the harsh Martian nights.

The plan forward is to fly Ingenuity in a manner that does not reduce the pace of Perseverance science operations. We may get a couple more flights in over the next few weeks, and then the agency will evaluate how we’re doing. We have already been able to gather all the flight performance data that we originally came here to collect. Now, this new operations demo gives us an opportunity to further expand our knowledge of flying machines on other planets.

– Bob Balaram, Ingenuity Chief Engineer, NASA/JPL

Prior to the 5th flight, NASA issued an audio recording captured by Perseverance of Ingenuity’s 4th flight – something the mission teams had been hoping to do.

The recording is a fascinating demonstration of the difference in how sound travels on Mars compared to Earth. Given the speed the rotors on Ingenuity spin (2400 rpm), one might expect the helicopter to generate the same high-pitched whine common to radio control helicopters on Earth. However, as the recording reveals, the less-dense atmosphere of Mars reduces the motor sounds from Ingenuity to a low-pitched hum. When listening, also note the doppler shift created by the drone’s motion away from, and back towards, the rover.

A  Brief Round-Up

China’s long March 5B Returns

As I reported in my previous Space Sunday  update (see: Space Sunday: a helicopter, a space station and a big ‘plane), China recently launched the core module of its new Tiangong space station using its massive Long March 5B booster. Following the successful launch, however, China effectively abandoned the 23-tonne core stage of the booster, demonstrating little care for where – or when – it might re-enter the atmosphere, and how much might survive.

Again, as I noted in that report, it’s not the first time China has taken a cavalier attitude towards the risk of such uncontrolled re-entries: the country has been responsible for 50% of the 6 largest uncontrolled re-entries in the history of space flight. In particular, the country has made no attempt to equip the Long March 5 series with the systems that would allow them to direct the heavy core stage into a controlled entry into the upper atmosphere where it might safely burn-up.

A particular worry with this Long March 5B was that its orbital track took it over several large population centres, including New York and Beijing – and it was not clear where or when it is orbit it might actually re-enter the denser atmosphere.

This finally happened at 02:15 UTC on Sunday, May 9th, when the booster was over the Arabian Peninsula. Several parts of the vehicle survived the initial re-entry, falling to Earth and striking the Indian Ocean north of the Maldive islands. Whilst no-one was injured, the situation has again led to widespread calls for China to be more responsible with its space activities.

The Long March 5B rocket (left) and the Tiangong space station. The rocket was responsible for putting the Tianhe-1 core module of the station into orbit on April 29th. Credit: China State Media

Starliner’s Second Flight Set for July

NASA and Boeing are now targeting July 30th for the 2nd uncrewed test flight for Boeing’s CST-100 Starliner capsule, designed to work alongside the SpaceX Crew Dragon to carry astronauts and equipment to and from the International Space Station (ISS).

The launch, is a follow-on to the first ucrewed test flight of the vehicle in December 2019, when software issues ultimately resulted in the vehicle being unable to rendezvous with the ISS. This resulted in NASA recommending more than 80 corrective actions to be taken with the vehicle and its pre-flight processing, with a second uncrewed flight required to confirm these corrective actions.

Due to lift-off at 18:53 UTC on July 30th, the second flight for Starliner should be a re-run of the first flight, placing the craft in orbit, then allowing it to make an automated flight to, and rendezvous with, the ISS.

SLS Core Stage Now at Kennedy Space Centre

Following the successful Green Run Hot Fire test of its four main engines in January (see: Space Sunday: SLS roars, LauncherOne flies and a mole dies), the core stage of NASA first Space Launch System booster arrived at Kennedy Space Centre at the end of April 2021, becoming the last major component of the rocket to arrive at the space centre in preparation for its upcoming flight.

The transport barge Pegasus arrives in the barge basin at Kennedy space Centre, April 27th, carrying the core stage of NASA’s first SLS booster. In the background is the giant cube of the Vehicle Assembly Building, and in front of in, the Launch Control Centre that manages NASA launches. Credit: NASA

Delivered by the transport barge Pegasus, after a trip by water from Mississippi the core stage completed the final part of its journey – the short distance between the barge delivery basin and the Vehicle Assembly Building (VAB) – by road.

Following its transfer to the Vehicle Assembly Building, the core stage will be stacked with the two solid rocket boosters that will assist it during launch, and integrated with its upper stages.

The SLS core stage being rolled from the barge to the VAB. Credit: NASA

NASA is targeting the end of 2021 for the first SLS flight. However, it faces a significant uphill climb to meet this date; not only is spare time in the project exceptionally short, this is the first time the workflow for integrating an SLS vehicle and preparing it for flight has been run – so it is more than likely delays will occur.

As such, NASA’s new Administrator, Bill Nelson has indicated the flight will likely slip in 2022. Nevertheless, the arrival of the core stage marks a further significant milestone for the SLS project.