Space Sunday: crashes, tests and an Inspiration

Two seconds from disaster: an inverted starship prototype SN9 about to impact the landing pad at Boca Chica, February 2nd,2021. Directly below the vehicle and on the horizon is the angled base of the Super Heavy launch platform (under construction). Centred on the ground is the Starhopper test vehicle with the SN7.2 test tank to the right. Image credit: Cosmic Perspective

On Tuesday, February 2nd, and after Federal Aviation Authority (FAA) related delays, SpaceX starship prototype SN9 took to the skies over southern Texas in the second high altitude flight test for the starship programme.

The flight itself, to some 10 km altitude, followed by a skydive descent to around the 2 km altitude mark, was remarkably successfully – as was the case with the first high-altitude flight (to 12 km on that occasion) seen with starship prototype SN8 in December 2020 (see: Space Sunday: the flight of SN8 and a round-up). However, and also like the SN8 flight, things went off-kilter during the final element of the flight, resulting in a complete loss of the vehicle.

Lift-off: SN9 rises from its launch platform with SN10 beyond it. he angle of this shot makes the two vehicles appear closer than they were in reality; SN10 was in fact well clear of its sister. Image credit: LabPadre

As I’ve previously noted, the route of staship prototype SN9 from fabrication high bay to launch stand had been remarkably fast compared to that of SN8, leading to speculation that the anticipated second flight test could occur in January. However, while the vehicle remained on the launch stand going through numerous pre-flight tests, including numerous Raptor engine re-start tests (which actually saw two of the motors swapped-out), things appeared stalled before that final step of an actual flight.

This now appears to be down to the fact that the FAA weren’t entirely happy with SpaceX over the flight of SN8, which effectively went ahead without proper approval. In short, SpaceX applied for a waiver against the licence the FAA had granted for starship flight testing which would have allowed the company to exceed “maximum public risk as allowed by federal  safety regulations”.

At the time, the waiver was denied – but the SN8 launch went ahead, violating the required safety limits, and whilst no-one was injured in the crash of SN8, the FAA correctly ordered a full investigation into the flight and also the safety culture and management oversight of SpaceX operations. Those investigations not only took time to complete, but also afterwards required FAA review and make modifications to the licence granted to SpaceX to carry out starship prototype flights.

Boca Chica from space: captured by a SkySat satellite approximately 568 km above the Earth, this image shows the SpaceX Boca Chica launch facility with the two Starship prototypes on their launch stands, the SN7.2 tank test unit, the Super Heavy booster launch stand under construction, and other elements such as the fuel farm, and Highway 4 running from the coast (r) back to the SpaceX construction and fabrication facilities (off to the left of the image). Image credit: Planet Labs
If a licensee violates the terms of their launch license, they did so knowing that an uninvolved member of the public could have been hurt or killed. That is not exaggeration. They took a calculated risk with your life and property … If the FAA does not enforce their launch licenses, it will damage the long-term viability of the launch industry and damage their credibility with Congress. It is possible that the industry could suffer significant regulatory burdens enforced by Congress to ensure safety.

– Former deputy chief of staff and senior FAA adviser Jared Zambrano-Stout,
commenting on SpaceX launching SN8 without the request licence waiver

The required licence modifications were not completed until February 1st, the day on which SpaceX initially attempted to launch SN9, and their lack of their availability may have been the reason that attempt was scrubbed, resulting in the February 2nd attempt.

Coverage of the test flight started very early on the morning (local time) on February 2nd, with SpaceX providing multiple camera points around the launch stand and on the vehicle, as well as via drones flying overhead In addition, spaceflight enthusiast such as also provided coverage from multiple points around the Boca Chica, Texas, site, including video recorded by Mary “BocaChicaGirl”, who provides a daily 24/7 feed of activity at the site.

The vehicle, with prototype SN10 occupying a second launch stand nearby, lifted-off at 20:25:15 UTC, following a 25 minutes delay due a range safety violation – one of the circumstances of concern to the FAA. However, the ascent itself was flawless, with the vehicle rapidly climbing to altitude over the next four minutes, two of the Raptors shutting down as it did so to reduce the dynamic stresses on the vehicle in light of it being only partially fuelled and to ensure it didn’t overshoot the planned apogee for the flight.

Flip over: at 10 km altitude, the one operational Raptor motor gimbals its thrust as the leeward midships RCS thruster fires, tipping SN9 over to start its 2-minute skydive back to the ground. Image credit: SpaceX

This came at 20:29:15 UTC, with the vehicle entering a brief hover using its one firing motor, as fuel supplies were switched from the main tanks to the smaller “header” tanks that would be used to power the engines during landing manoeuvres. At this point, the remaining motor shut down as the reaction control  system (RCS) thrusters fired, gently pushing the vehicle over from vertical and into its skydive position, where the fore and aft aerodynamic surfaces could be used to stabilise the vehicle during descent.

This phase of the descent lasted just over 2 minutes, with the order given to re-start two of the Raptor engines given at 20:31:35 UTC. These engines should have then gimballed and used their thrust, together with the forward RCS thrusters to return the vehicle to a vertical pose before one of the motors again shut down and the second slowed the vehicle into a propulsive, tail-first landing.

From below: a camera on the ground dramatically captures the moment one of the Raptor engines on SN9 re-starts as RCS systems fire to help maintain stability. Image credit: SpaceX

Both of these motors fire a split second apart, and footage of the rear of the vehicle suggests that the first may have suffered a mis-fire before starting correctly. However, the second motor appears to have suffered a catastrophic failure on re-start, possibly involving a turbopump failure: as it ignited, debris could clearly be seen being blown clear of the vehicle.

With only one operational main engine, SN9 was unable to stop its change in flight profile and remain upright. Instead, it continued to rotate and become inverted just before it struck the landing pad in what SpaceX refer to as “an energetic, rapid unscheduled disassembly” (that’s “exploded on impact” for the rest of us).

No official word on the failure has been given – obviously, SpaceX will need time for a thorough investigation, and will likely have the FAA watching closely. It is also not clear if the material coming away from the vehicle is actually parts of the engine, or sections of the engine skirt blown clear of the vehicle. As some are still to be drifting down to the ground fairly close to SN10 on its launch stand, it is possible they are from the vehicle’s skin.

A wider image of the inverted SN9 prototype just before impact, with the Super Heavy launch stand, SN7.2 tank and Starhopper prototype overlapping one another, and the SN10 prototype to the right. Note the debris (arrowed) drifting down behind the vehicle. Image credit:

However, the incident, together with SN8’s failure, highlights an intrinsic weakness in the current Starship flight envelope: if one of the two motors on a descending vehicle misfires or fails, it will result in the catastrophic loss of the vehicle. Period. For test and uncrewed flights, this isn’t an issue; but if starship is ever going to be certified for transporting humans to / from orbit, such a single point of failure most certainly is.

Given this, SpaceX look to be taking steps to mitigate the issue, such by re-starting all three motors and then shutting one down once the flight system confirms it has at least two firing smoothly. Whether or not this would overcome all concerns about the safety of the vehicle when returning to Earth is open to debate; however, it appears as if this might be the procedure SpaceX will use for Starship SN10’s coming flight.

A still taken from video footage captured by a camera within the engine skirt of SN9 (r) appears to show a fire outside of the exhaust bell of the second Raptor engine that should have restarted, prompting speculation it may have suffered a significant turbopump failure. Image credit: SpaceX with arrow annotation by Marcus House

When that flight will come is unclear; the vehicle is still in the process of having its Raptor engines mounted, and it is unlikely any flight will come prior to the loss of SN9 being thoroughly understood in terms of actual cause. When it does happen, SN10’s flight will be slightly different to SN8 and SN9, in that the vehicle will fly with section of his hull covered in heat shield tiles – around 213 in one section, with three more smaller areas also covered.

These aren’t included to test their ability to withstand heat, however.  Rather they are being used to test the bonding agent that fixes them to the starship hull. The latter experiences a wide range of temperatures that are radiated outwards. he hull around the main fuel tanks – a location where the large block of 213 tiles sits – experiences super-low temperatures when loaded with liquid fuel stock; the skirt around the tail of the vehicle conversely experiences high temperatures when the engines are firing, while other sections can experience both high and low temperatures  side-by-side.  So understanding how the bonding agent reactions to all of the extremes, and how well the tiles remain fixed to the vehicle is an essential part of gathering data on starship and its flight characteristics.

In the meantime, catch this incredible slow motion playback of SN9’s moment of impact, by Cosmic Perspective.

NASA Confirms another Static Fire Test for SLS Core-1

In January I reported on NASA’s “hot fire” test of the first core stage of their new Space Launch System (SLS) rocket that is key to the agency’s plans to return  humans to the surface of the Moon, and to reach further afield in space with both crewed and robotic missions.

The test saw the first stage of the massive rocket fire all four of its shuttle-derived RS-25 main engines for 8 minutes – the time they would run for during an actual launch – with the core stage bolted to a test stand at the agency’s Stennis Space Centre, Mississippi. During that time, the engines should have been put through a series of tests designed to simulate their operations during an orbital ascent,  prior to being shut down.

Had it been successful, the test would have cleared the stage for transfer to NASA’s Kennedy Space Centre, where it would be assembled with the rest of the rocket in preparation for the first SLS-Orion launch, which is currently still scheduled for the end of 2021.

The January 16th 2021 hot fire test of the SLS RS-25 main engines ended abruptly as a result of a software-driven shut-down of the engines caused by too strict test parameters being applied. Image credit: NASA

However, after running for just 67 seconds, software monitoring the test ordered all four engines to shut down to avoid exceeding test parameters that were intentionally restrictive. In the period immediately after the January 16th test, it had been hoped sufficient data on engine performance had been gathered in order to forego a further test, allowing the core stage to be evaluated and then removed from the test stand to start the journey to Kennedy Space Centre.

It has now been decided that a second hot fire test for the stage is required, and has been targeted for the week commencing Monday, February 22nd.

NASA do not believe the need for a second engine run test will significantly impact the launch schedule for the mission, Christened Atemis-1, and work is continuing on preparing other elements of the vehicle at Kennedy Space Centre – most notably the stacking of sections of the twin solid rocket boosters (SRBs) that will help propel SLS launch vehicles toward orbit.

The two base sections of the solid rocket boosters (SRBs) that will be used for the Artemis-1 mission are stacked over their rocket motor skirts in the Vehicle Assembly Building at NASA’s Kennedy Space Centre. These booster will eventually brace the SLS rocket on either side at launch. Image credit: NASA

Also, while doubts had been cast over the future of the programme as a result of a new incoming President and his administration, the Biden White House has indicated support for Artemis and a human return to the Moon – although not necessarily by 2024.

Mars Missions Approach Target

February will see three new missions arrive on, or around Mars, hopefully opening up three new chapters in our efforts to understand the Red planet.

The first mission that’s due to arrive is the UAE’s Hope orbiter. This is due to enter orbit around Mars on Tuesday, February 9th, when at 15:41UTC the craft will fire its thrusters for 27 minutes in order to slow itself sufficiently to be captured by Mars’ gravity and pulled into orbit. However, the team behind the mission, which marks not only the first attempt by the UAE to reach Mars, but also their first interplanetary mission ever, are understandably nervous.

This is because Mars is a notoriously difficult destination to reach; between 1/ and 1/2 of all missions sent there have failed for assorted reasons. In fact, to achieve orbit, Hope must burn half of its available reserves of propellant. Should it burn too little, it could simply dash by Mars and on into the outer solar system, should it burn too much, it will slam into the tenuous Martian atmosphere and burn up. As such, the manoeuvre has been simulated by the mission team on numerous occasions, and the thrusters tested several times- but nerve are still on edge pending the completion of the manoeuvre.

24 hours after Hope completes its manoeuvre, the Chinese Tianwen-1 mission should likewise enter orbit. Massing 5 tonnes, this is a significantly bigger vehicle than the UAE’s Hope. It is also far more complex, comprising an orbiter, a lander and a rover. Again, assuming orbital insertion is successful, the combined vehicle will remain in orbit for a period of time, where among other things it will ensure the viability of the selected landing zone prior to dispatching the lander / rover to the surface of Mars.

China’s Tianwen-1 mission should enter Mars orbit on February 10th, 2021. It will deliver a lander and rover to the surface of the planet some time around April 2021. Image credit: CASC

Finally, just over a week later, on February 18th, NASA’s Mars 2020 mission is set to deliver the Perseverance rover and Ingenuity helicopter directly to the surface of Mars in what is likely to be the most heart-stopping event of the month for a space mission.

I’ll hopefully have positive news on both Hope and Tianwen-1 in my next update, and a special report on  Mars 2020 the week after.

Inspiration4: The First “All Civilian” Space Flight

Jared Isaacman may not be a name everyone is familiar with.  However, he is the founder and CEO of payments processing company Shift4 Payments, and the company has made him a billionaire. He’s also a pilot and a philanthropist – in 2008 he completed a record-breaking flight around the world in a light jet, raising money for the Make-A-Wish foundation.

Now he is teaming up with SpaceX to raise money for St. Jude Children’s Research Hospital in Memphis, Tennessee, a leading centre for providing free treatment and care for children suffering from a range of illnesses, including cancer.

Jared Isaacman poses in a training simulator of the SpaceX Crew Dragon vehicle for Inspiration4 publicity images. Image credit: SpaceX
He has done so by chartering an entire SpaceX Crew Dragon space vehicle for an orbital flight around the Earth, a flight that is being called Inspiration4. One of the four seats on the flight will be taken by Isaacman as flight commander, whilst the remaining three seats will be awarded to members of the general public.

One will go to a worker from St. Judes; the second will be drawn in a raffle of people who have been encouraged to donate to the hospital, and the third will be drawn from a competition for  entrepreneurs run by Isaacman’s Shift4Shop.

The selected three will join Isaacman in full commercial astronaut training provided by SpaceX and paid for by the billionaire. Providing they pass this training and associated medical and stress tests, they will join Isaacmen aboard the Crew Dragon capsule Resilience, which at the time of writing is docked at the International Space Station, and launch from Kennedy Space Centre and complete several orbits of the Earth before re-entering that atmosphere and splashing down off the Florida coast.

In completing the flight, which is being targeted for the end of 2021, they will become the first “all civilian”, non-governmental crew of a space flight, this the Dragon vehicle operating in its fully autonomous mode  oversee by SpaceX’s mission team on Earth.