Space Sunday: how to fly your Dragon

The International Space Station imaged from 200 metres by the docking systems camera looking out of the forward hatch window of SpaceX Crew Dragon Endeavour. Credit: SpaceX / NASA

On Saturday, May 30th, 2020 the United States successfully launched astronauts into orbit from American soil for the first time since July 8th, 2011. It came after an initial attempt on May 27th, 2020 had to be scrubbed (called off) due to adverse weather conditions putting the launch vehicle at risk of a possible electrical strike.

As I noted in my previous Space Sunday piece, the primary goal of the mission is to confirm the SpaceX Crew Dragon vehicle is ready to commence operations ferrying crew to and from the International Space Station. Intended to fly up to four crew at a time on such missions, for this final test flight, Crew Dragon lifted-off with only two crew aboard: NASA veterans Robert L. Behnken (flight pilot) and Douglas G. Hurley (commander).

NASA astronauts Bob Behnken (l) and Doug Hurley, photographed at the top elevator station at Launch Complex 39A, Kennedy Space Centre, at a dress rehearsal for the Crew Dragon Demo-2 flight, May 24th, 2020. Credit: SpaceX

Weather was also a concern in the run-up to the May 30th launch, with NASA putting a chance of lift-off at 50/50 through to less than an hour ahead of the launch time. However, after a burst of rain in the area of Kennedy Space Centre as the Falcon 9 launch vehicle was being prepared for lift-off, the weather situation both around the Florida Cape and downrange of the launch site and along the track of the vehicle’s line of ascent, cleared sufficiently for the launch to go ahead.

The entire launch, from the astronauts suit-up in the crew room at Kennedy Space Centre, through lift-off, ascent to orbit, on-orbit operations and the rendezvous and docking with the International Space Station some 19 hours after launch, was covered entirely live through NASA TV and SpaceX on You Tube and other channels. This coverage made it one of the mos-watched launches of a space vehicle despite the limitations of travel in place due to the SARS-CoV-2 pandemic, with 1.5 million people watching the SpaceX relay of the NASA feed alone.

Thursday, May 21st, 2020: The Falcon 9 / Crew Dragon vehicle bearing the NASA worm and meatball logos, rolls out of the SpaceX vehicle processing building en route to pad 39A

Following their arrival at the launch pad some 2+ hours ahead of the the launch, the astronauts – known as “the Dads” to the SpaceX team – travelled to the top of the launch tower prior to ingressing into the Crew Dragon vehicle and performing a series of pre-flight checks both before and after the crew hatch was closed-out by the fight support crew.

At around an hour prior to launch and with the flight support crew clear of the tower, the access arm was rotated clear and fuelling of the Falcon 9’s first and second stage tanks commenced as the weather clearance was given. Unlike Apollo and the shuttle, the SpaceX vehicles go through fuelling as a last stage of ground operations to minimise the amount of fuel venting / topping-up that is required as the super-cold liquid propellants start to slowly warm despite insulation and cooling.

Ahead of the launch, the ISS passed over Kennedy Space Centre and this photograph was taken. Centre top is the massive Vehicle Assembly Building where the SLS will be assembled for launch and the former Orbiter Processing Buildings, one of which is now used by Boeing for the Starliner crew vehicle and another by the Orion MPCV; The crawler / transporter track runs from the VAB toward the coast, splitting so one leg runs to the right and Pad 39B, which will host the SLS, while the second runs down to Pad 39A where the white SpaceX vehicle assembly building can be seen, with the Falcon 9 on the pad. Credit: NASA

A crucial aspect of the Demo-2 launch was that orbital mechanics demanded the vehicle had to lift-off precisely on time – there could be no “holds” that delayed it beyond the appointed lift-off time. Were launch to be delayed, even by a few minutes, the Crew Dragon would reach orbit at the wrong point related to the ISS, and so and rendezvous would be much harder, if not impossible, given what needed to be achieved in the flight ahead of reaching the space station.

So, at 19:22:45 UTC, precisely on schedule, the nine motors of the Falcon 9’s first stage igniting, lifting the black-and-white rocket and capsule vehicle smoothly off the pad. This marked a further first for the mission: not only was it the first US crewed mission into space undertaken from US soil bult and operated by a private company, the entire launch process was run by SpaceX and not by NASA’s Mission Operations Control Room (MOCR – or “moe-kerr”) at the Johnson Space Centre (JSC), although the latter were obviously looking over SpaceX’s shoulder and monitoring things, with the ISS Fly Operations Centre fully “in the loop”.

A Dragon rises with its riders as the Falcon 9 clears the tower at LC-39A, May 30th, 2020. Credit: NASA live stream

Ascent to orbit lasted some 8 minutes – although to all those watching, it probably seemed a lot quicker. Powering the vehicle through the denser part of the atmosphere, the Falcon’s first stage reached MECO (main engine cut-off) just over 2 minutes after launch. Separating, this continued along a ballistic trajectory, flicking itself around to deploy vanes to help with its descent back though the atmosphere so it might make a landing on the autonomous drone ship Of Course I Still Love You.

Camera footage from the first stage, transmitted as the Falcon’s second stage continued to boost the Crew Dragon vehicle to orbit, showed it orienting itself using its attitude thrusters, prior to three of the Raptor engines firing to slow it down and cushion it as it dropped back into denser atmosphere. From here, it dropped smoothly back towards the drone ship, the deployed vanes holding it upright. Unfortunately, video footage was lost prior to touch-down, but moments later, the feed resumed, showing the stage sitting on the ship’s deck as high above, the Falcon’s second stage reached SECO – Second (Stage) Engine Cut-off, and shortly after, the Dragon separated from it.

Timing in the flight meant that the Falcon 9 first stage successfully landed on the autonomous drone ship Of Course I Still Love You (l) at almost the same time as SECO was reached by the rocket’s upper stage, followed a couple of minutes later by Crew Dragon successfully separating from the second stage (r). Credit: SpaceX

After their arrival on the ISS, Hurley and Behnken were asked to compare the launch with their experiences of (between them) four shuttle ascents. Both agreed that the lift-off itself was a lot smoother than shuttle, whilst ascent felt rougher. Behnken noted that with the shuttle, the first two minutes of a launch – up to the point of the two solid rocket booster being detached – was always rough, but after that point, with just the shuttle’s own engines firing, things would “smooth out”, but with Falcon, the general vibration and noise didn’t let up until SECO was reached.

Once on-orbit, the two men completed a further series of checks prior to doffing their pressure suits and getting into shirt sleeves ready to commence a series of flight tests to see how Crew Dragon handled under manual control. This point in the flight also allowed them to reveal they had a stowaway hitching a ride, a sequin encrusted apatosaurus that quickly became the flight’s “aero-g indicator” for people watching the live stream.

15 minutes into the mission, and a last look at the Crew Dragon vehicle as it passes out of range of the on-board camera. Credit: SpaceX

We did end up with one stowaway on board our vehicle when we launched today. It was not just Doug and I who accomplished the launch here. We do have an Apatosaurus aboard. We both have two boys who are super interested in dinosaurs. We collected up all the dinosaurs between our two houses and ‘Tremor,’ the Apatosaurus, got the vote from the boys to make the trip into space today with us.

– Bob Behnken, explaining the “stowaway” on Demo-2.

During this period, the crew also revealed the name they had selected for their capsule: Endeavour, making it the third space vehicle to carry the name into space after the Apollo 15 Command Module and the the last of the space shuttles to be built.

The view from the station as Crew Dragon sits below the station, its nose cone raise to expose its docking mechanism and hatch. Credit: NASA

In order to rendezvous with the ISS, Endeavour had to increase its altitude through a series of burns, some of which took place before the crew got some sleep, and some after, when they were once more in their futuristic pressure suits (a precaution against any accident that might damage the capsule).

The latter started with a few slow burns that lifted the Crew Dragon so its track would cross that of the space station, somewhat astern of it. At that point, thrusters would fire, placing Endeavour on precisely the same orbit as ISS, but around 200 metres behind it.

Inside Endeavour: on the centre screen, the track of Endeavour can be seen arcing upwards to intercept the track of the ISS,a white dot showing where the vehicle must come to a “stop” to be aligned with the station’s docking port. On the left, on the screen in front of Hurley is an image from the the docking camera showing the ISS. Credit: SpaceX

This point was approached very slowly and gently: while both station and craft were orbiting the earth at  28,00 km/h, Endeavour closed on the station at less than 1/2 a metre a second. Part of this approach was made in the Earth’s shadow – night-time for ISS and Crew Dragon – and the high-resolution remote camera on the space station caught am image of Endeavour against a backdrop of city lights over Japan that looks like a starfield, the red and green collision lights on the capsule resembling eyes staring back at the ISS.

Once on the same track as the station, Hurley again took over manual control, putting Endeavour through a series of gentle manoeuvres that carried it out of alignment with the the ISS docking port, before he carefully brought the vehicle back into alignment, thus testing how well Dragon handled under manual control whilst in close proximity to the station, and how the touch screen flight controls and the touch-sensitive suit gloves he was wearing worked together outside of the simulator.

Endeavour at 20m from the ISS. With the nose section raised (done shortly after reaching orbit), the forward end of the vehicle can be seen.

At its centre is the docking hatch with the docking camera mounted on it. The grey ring is the “soft capture” ring. The four black dots of the forward RCS thrusters can be seen.

Further back along the hull, the blue NASA logo and the US flag mark two of the capsule’s four pairs of SuperDraco motors. Beyond those is the half-black / half-white hull of the the “trunk” – the service module the supplies Crew Dragon with power. Credit: NASA

With these tasks done – and Hurley reportedly reluctant to stop enjoying himself at the controls (according to a joking Behnken) – flight operations were switched back to automatic mode, and the Endeavour slowly crept in to the station, extending its “soft dock” ring from the open nose cone section, making smooth initial contact with a port on the station’s docking adaptor at 14:16 UTC.

At this point, the capsule took over control of the station’s own thrusters, and used them to hold things steady as the “soft capture” ring retracted into Endeavour’s nose, pulling it into full contact with the docking adaptor so 12 “hard capture” hooks to connect the two together and an airtight seal between them form.

Contact! Seen from a remote camera on the Japanese module of the ISS, Endeavour achieves soft capture of the station’s docking port adapter. Credit: NASA

Several hours of operations then followed – Hurley and Behnken powering-down the capsule’s flight systems and ISS Expedition 63 commander Chris Cassidy, prepped the docking adaptor ready for Behnken and Hurley to egress their vehicle while Russian cosmonauts Anatoli Ivanishin and Ivan Vagner, monitored the station and the link-out of “hard” power and communications links (the latter of which gave some initial trouble) with the Endeavour, which will remain docked with the ISS for the next several weeks (and possibly longer, depending on NASA’s requirements).

At 18:22 UTC, after all the checks were completed and the “vestibule” – the space in the nose of the Crew Dragon housing the docking mechanisms that had been open to space since on-orbit arrival – pressurised, the hatch was opened and Behnken and Hurley boarded the ISS, the latter bumping into a unit in the Columbus module of the station in the process and slightly cutting his forehead, the one mishap of the flight! After warm greetings between Dragon and ISS crews, their was a protracted “Welcome Aboard ceremony” before the crews could finally be given at least some peace and quiet.

With the success of this flight – and allowing for its safe return to Earth, NASA and SpaceX are now very close to being able to start “routine” crew flights to and from the ISS, the first of which – Crew-1 – is set to carry NASA astronauts Mike Hopkins,
Victor Glover and Shannon Walker, together with Japanese astronaut Soichi Noguchi to the station at the end of August 2020.

In the meantime, if you fancy trying your hand “flying” a Crew Dragon into a safe docking with the International Space Station, why not try the SpaceX ISS docking simulator.

You can try your own hand of Crew Dragon / ISS docking using the SpaceX on-line simulator. I did! 🙂

Starship Prototype Explodes

Prior to the Demo-2 flight, SpaceX suffered a further setback with its plans to start text flights of its Starship prototype vehicles, when the fourth prototype was dramatically destroyed during a test firing of its engines, marking it as the fourth of five prototypes to be destroyed during testing thus far.

The test, on May 29th, was the second such engine test for the vehicle, building on the success of tank pressurisation tests and an first engine test, all of which had proven so successful, SpaceX had secured clearance from US Federal Aviation Administration to carry out the first actual flight of the vehicle on June 1st, 2020. The test itself – a two-minute firing of the Raptor engine – was actually successful. However, as the vehicle stood on the pad, a failure appeared to occur at, or near, the base of the vehicle and it rapidly vented a mass of gas – possibly oxygen – that came into contact with an ignition source, resulting in a massive explosion.

Up until this point, SN4, seen in the video above sans the crew / cargo upper section, had been only the second of 5 prototypes to survive basic tank pressurisation tests, the other being prototype SN2 (now retired). Starship Mk1 , SN1 and SN3 all suffered failures that destroyed / severely damaged them.

SpaceX have yet to give an explanation for what actually occurred, but reports from their Boca Chica test centre indicate that focus has already shifted to the SN5 and SN6 prototypes, with fabrication starting on an SN7 vehicle as well.

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