Space Sunday: SpaceX Starship update

A Starship / Super Heavy pairing lifts-off from a dedicated launch facility in this still from an animated video produced by SpaceX for the September 28th, 2019 update. Credit: SpaceX

On the occasion of the eleventh anniversary of SpaceX achieving orbit for the first time with their Falcon 1 rocket on September 28th, 2008, CEO Elon Musk presented an update on the company’s progress developing its massive Super Heavy booster and interplanetary class vehicle, Starship.

It has been some 12 months since the last update on the development of the two vehicles – the last update really being overshadowed by the announcement SpaceX planned to fly a Japanese billionaire and his entourage around the Moon and back (see Moon trips, Mr Spock’s “home” and roving an asteroid for more), and the programme has moved on significantly since then, as indicated by the fact that the 2019 update took place at the SpaceX facilities in Boca Chica and against the backdrop of the first of the Starship prototype vehicle.

Starship Mk1 under construction at the SpaceX facilities near Boca Chica, Texas. Credit: unknown

Since its first public unveiling in 2016, the Starship / Super Heavy combination has been through a number of iterations and name changes. However, it is fair to say that things have now settled down on the design front, and what was presented at Boca Chica is liable to remain largely unchanged, assuming everything proceeds as SpaceX hopes.

In this, the flight capable prototype Starship at Boca Chica is the first in a series of such vehicles. A second is  under construction at the SpaceX facilities in Cocoa, Florida, and three more are planned, one of which will be used to make the first orbital flight within the next 6 months, and Musk suggesting another could be used in a crewed orbital flight within the next 12 months – which sounds exceptionally ambitious. Construction of the two initial Starship prototypes has not exactly been secret: both have been literally assembled in the open. So even ahead of the September 28th event, some were already developing renderings of the new Starship design compared to the last known iteration.

A rendering by Kimi Talvitie comparing the 2018 design for Starship (l) with the prototype (r). The rendering of the 2019 prototype was based on direct feedback from Elon Musk

The new design sees some significant changes in Starship – notably with the fins, canards and landing legs. The 2018 variant was marked by three large fins, two of which would be actuated (hinged for up / down motion relative to the hull) for atmospheric flight, with all three fins containing the vehicle’s landing legs. At the time of that design, I commented that this approach appeared risky: a heavy landing on the Moon or Mars might conceivably damage one of the actuated fins, affecting the vehicle’s ability to undertake atmospheric flight on its return to Earth.

With the new design, the fins are reduced to two and reshaped, both of which are actuated to hinge “up” and “down”. In addition, the landing system is now independent of the fins, removing the greater part of the risk of damaging them on landing. The number of landing legs is also increased to six. At the forward end of the vehicle, the canards are enlarged and hinged in a similar manner to the fins.

Starship’s basic specification. Note the “dry” mass of 85 tonnes is incorrectly stated in the slide: it is expected the production version of Starship will mass around 120 tonnes (the prototype masses around 200 tonnes. Credit: SpaceX

The remaining aspects of the design are more-or-less unchanged as far as the body of the ship is concerned: it will be some 50 metres (162.5ft) in length and have a diameter of 9m (29ft). The forward end of the vehicle will be given over to crew and passengers or cargo (or a mix of the two), although Musk now estimates the vehicle will – with the aid of the Super Heavy booster – be lifting up to 150 tonnes to low Earth orbit – an increase of roughly a third – and return up to 50 tonnes to Earth.

To help achieve this, the motor system has been slight revised. While six engines will still be used, three will now be optimised for vacuum thrust, ideal for orbital flight and pushing the vehicle out to the Moon or Mars, and the remaining three optimised for sea level thrust and capable of being gimballed for use during a descent through an atmosphere and landing.

Starship’s motor arrangement: three central Raptor engines optimised for sea level thrust and capable of gimballing and three outer vacuum optimised motors with fixed, large diameter exhaust bells for maximum efficiency. The “boxes” visible in the rendering are potentially additional cargo bins. Credit: SpaceX

During the presentation, Musk explained the rationale behind the use of 301 cold rolled stainless steel in the design, noting a number of reasons. Firstly, the cold rolling process results in a stronger, light finished product, and this becomes even stronger when exposed to the very low temperatures of cryogenic fuels. Thus, Starship and Super Heavy in theory have a structural strength equitable to that of carbon composites – but at a much lower overall mass.

Secondly, the cold rolled steel has very high melt temperatures, reducing the amount of direct heat shielding required, again reducing the vehicle’s overall mass. It is also both highly corrosion-resistant and easy to work with. This means that basic repairs to a vehicle on the surface of the Moon or Mars could be effected, or even that a Starship could even be dismantled and the steel from the hull re-purposed. Finally, there’s the fact that all these advantages are gained in a product costing around 2% that of an equivalent mass of carbon composite.

Starship Mk 1 filmed during the September 28th livestream event. Credit: SpaceX

In terms of heat shielding, the “windward” side of Starship (the side facing the fictional heat of entry into an atmosphere) will be coated with lightweight ceramic tiles. Somewhat similar in nature to those used within the space shuttle, they will be of a hardier material and less prone to damage. The re-entry profile was also discussed, with Musk comparing Starship to a sky diver.

To explain: the vehicle will approach the atmosphere at a relatively high 60-degree incidence, using the heat generated by contact with the upper atmosphere to slow its velocity from Mach 25 to a point where, once within the denser atmosphere, the vehicle is literally falling more-or-less horizontally. The fins and canards can then be used to maintain the vehicles orientation in a similar manner to that of a sky diver using his arms and legs. in addition, the lift generated by fins and canards will further help slow its descent until, roughly 2 km above the ground, the vehicle will rotate to a vertical position and use the three gimballed Raptor motors to make a propulsive, tail-first landing.

SpaceX plan to offer Starship in support of lunar operations – but the company’s goal is to establish a permanent human presence on Mars. Credit: SpaceX

Starship Mk 1 is equipped with the same sea level optimised Raptor motors as intended for the production vehicles.  SpaceX hope to see it make at least one flight before the end of the year – although the company has yet to secure a permit from the US Federal Aviation Authority to commence flights. This first attempt will be to an altitude of around 20 km (12.5 mi) before a descent and landing. If successful, the test programme involving the various prototype vehicles will unfold from there.

Turning to the Super Heavy booster, Musk indicated that there have been some changes here as well. In 2018 it was indicated that Super Heavy would use 37 liquid methane / liquid oxygen Raptor motors. This is now the maximum number of motors Super Heavy can use: the actual number will be variable depending on factors such as launch objectives and payload. However, it is anticipated Super Heavy will never fly with less that 24 motors.

The 2019 Super Heavy Design. Credit; SpaceX

Other design changes include revised fins at the lower end of the vehicle, which now have integrated landing pads, and revised actuated grid fins at the top of the booster that, as with the Falcon 9 core stage, are deployed during descent to both maintain its orientation and assist with descent guidance. With a combined length of 118m (387 ft) this iteration of Super Heavy / Starship retains the same overall height as the 2018 design.

SpaceX anticipate that test flights of the Super Heavy will commence from Kennedy Space Centre later in 2020, and will again initially test the vehicle’s launch and landing capabilities. It’s not clear when combined flights of Starship and Super Heavy will commence – or from where. The company has indicated it plans to build and operate the vehicles directly out of its existing facilities at Boca Chica; but this is also dependent upon a range of factors, including being granted the permission to build a massive and potentially disruptive space launch facility.

An unusual vehicle size comparison chart supplied by SpaceX. Credit: SpaceX

Musk has indicated that while SpaceX currently has less than 5% of its resources focused on the new launch system at present – the rest are allegedly focused on meeting commitments with Falcon launches and, particularly, getting the Crew Dragon ready to commence operations in ferrying astronauts to / from the ISS – he is also adamant the company is ready to “accelerate” Starship / Super Heavy construction. However, and again, Boca Chica lacks the facilities for indoor fabrication – and while the construction of the initial prototypes has been undertaken outdoors, it’s unlikely that trying to do the same with vehicles ultimately designed to carry passengers to and from orbit will be welcomed.

Time will tell on that. In the meantime, I’ll close with a video SpaceX has produced showing the updated system, and which includes Musk describing the need for on-orbit refuelling of one Starship by another – a critical need if the vehicle is to journey to Mars.

NASA “Demonstrates Commitment to the Moon”

On September 23rd, NASA announced it was awarding a contract to Lockheed Martin for long-term production of the Orion Multi-Purpose Crew Vehicle (Orion MPCV)  spacecraft, covering up to 12 spacecraft designed to meet NASA’s anticipated needs into the 2030s.

In total, the contract comprises the three Orion spacecraft required for the Artemis 3, 4 and 5 missions – the first three missions to deliver crews to the surface of the Moon (2024-2026) – for US $2.7 billion, and a further 3 for the Artemis 6 through 8 missions (2027-2028) for US $1.9 billion. An additional option in the contract allows for six further Orion vehicles to be delivered between up to 2030.

This contract secures Orion production through the next decade, demonstrating NASA’s commitment to establishing a sustainable presence at the moon to bring back new knowledge and prepare for sending astronauts to Mars.

– NASA Adminstrator, James Bridenstine

The Orion MPCV and Service Module – click for full size. Credit: NASA

The cost saving of US $800,000 between the two set of initial Orion vehicles is said to be due in part to reusability. The electronics and seating used for the Artemis 2 vehicle (crewed flight around the Moon) will be reused in the Artemis 5 Orion vehicle, while the entire crew module from Artemis 3 will fly again in the Orion vehicle for Artemis 6. The ability to re-use parts, coupled with the overall fabrication costs of these six vehicles will allow the additional 6 Orions to be ordered under firm fixed-price contracts.

It’s not clear if the contract extends to the Orion Service module, which is designed and manufactured by the European Space Agency (ESA). However, it does support the production and use of core Orion elements in NASA’s Lunar Orbital Platform-Gateway (LOP-G) without the need for the Gateway programme to develop and qualify similar components under separate contracts.

Space Pictures of the Week

The Soyuz Rises

This stunning image was captured and tweeted by astronaut Christina Koch on the International Space Station. It shows a bird’s-eye view of Soyuz MS-15 (ISS Expedition crew 61) climbing to orbit following its launch from Baikonur Cosmodrome in Kazakhstan, on September 25th, 2019. The contrail marks the ascent to orbit, while the semi-circular shock wave is the result of the upper stage motors having fired to separate the Soyuz space vehicle form the core stage, disturbing the tenuous upper atmosphere. Credit: Christina Koch (@Astro_Christina)

Mars 2020 Takes Shape

In an August 2019 video from NASA’s Jet Propulsion Laboratory, we’re given the chance to witness the development of the Mars 2020 rover vehicle. The video show the various elements of the mission: the cruise bus that contains various instruments for monitoring the environment around the vehicle and supplies the rover with power and heat, etc., during the journey from Earth to Mars; the aeroshell and heat shield that will protect the rover and its “skycrane” during their entry into the Martian atmosphere; the “skycrane” itself, that will winch the rover down to the surface of Mars whilst hovering on is rocket motors, and construction of the rover. Scheduled for launch in mid-2020, the rover will arrive on the surface of Mars in February 2021.

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