Space Sunday: 3D printed rockets; pi for a planet and solar cycles

A time-lapse image of a fuel tank for the Relativity Terran-1 rocket being constructed using 3D printing techniques. Credit: @thesheetztweetz

Not too many years ago, the only organisations that were seen as being able to operate space launch systems were governments, notably the United States, Russia, Japan, China and India, although France has a long track record of launch vehicle development, while  nations like the UK have also dipped a toe or two into the waters.

However, over the last 20 years, we’ve seen a major paradigm shift with launcher development that has seen much of it move away from government-sponsored development and purely into private hands (although actual launch contracts awarded by governments can oft help grease the wheels of commerce for these companies).

The most obvious commercial launch vehicle developers have frequently been mentioned in these pages: SpaceX, Blue Origin, United Launch Alliance, Northrop Grumman, and so on (note I’m deliberately avoiding certain names such as Arianespace, because while they are the oldest commercial launch provider in the world, they don’t actually develop the rockets they launch; and the big boys of Boeing and Lockheed Martin, as outside of their involvement in ULA, they are focused on government-funded launch vehicle development).

However, there are many, smaller commercial companies that are involved in launch vehicle development and operation. Two of the more interesting of these are Rocket Lab, which I have mentioned in these pages in the past, and Relativity Space.

Founded in 2006, Rocket Lab is the mini-me SpaceX of small payload launchers. Established by its current CEO, New Zealander Peter Beck, the company originally operated in Auckland, New Zealand, but now is primarily headquartered in the United States as a US company  (the New Zealand arm being a wholly owned subsidiary).

The Electron rocket with Rocket Labs’ CEO, New Zealander Peter Beck

Rocket Lab operates the Electron Rocket, flying commercial payloads of up to 300 kg to low Earth orbit (LEO) or up to 200 kg to a sun synchronous orbit (SSO). A two-stage vehicle, Electron uses the electric pump-fed Rutherford rocket motor in both stages, making it the first launch system to use an electric pump system to deliver fuel to the engines.

Currently an expendable launch system, Rocket Lab plan to follow in the footsteps of SpaceX and make the first stage of Electron reusable, although they will not be using a propulsive landing system like SpaceX, but will use parachutes / a parafoil. In addition, the company plans to start providing customers with an optional third stage for the vehicle that can provide a “kick” to motor payloads can use to circularise their orbits.

Up until the time of writing, the company has only launched out of a purpose-built facility on the Mahia Peninsula on New Zealand’s North Island, where it has a 30-year licence to launch rockets every 72 hours. To help with this, the facility offers two launch pad complexes; however, the real ability to meet such a high rate of launches (assuming Rocket Lab grows the customer list it needs to warrant such a fast launch rate) is in the rocket fabrication and assembly process.

The extensive use of composites in the fabrication of both the Electron rocket and its motors means that Rocket Lab can fabricate and assemble a launch vehicle every seven days.  Credit: Rocket Lab

Thanks to the high use of composite throughout the Electron and its motors which accounts for around 95% of parts in both, Rocket Lab has been able to develop a fully automated and very flexible fabrication facility that can produce all the composite parts for the single launch vehicle in just 12 hours. This in turn allows the company to assemble and test a new rocket every seven days.

Starting in 2020 – and potentially in the next couple of weeks – Rocket Lab will commence launch operations from the Mid-Atlantic Regional Spaceport, Wallops Island, Virginia, USA (located at the southern end of NASA’s Wallops Flight Facility). Should it go ahead, the UK’s proposed Sutherland Spaceport, Scotland, may also become a base of operations for Rocket Lab, offering launches alongside the UK’s Orbex, a company a small-scale, reusable launcher capable of delivering up to 150 kg to a 500 km SSO.

Through the long grass – an Electron Rocket undergoing static tests at Rocket Lab’s new launch facilities at the Mid-Atlantic Regional Spaceport, Wallops Island, Virginia, USA. Credit: Rocket Lab

As well as the commercial launch capabilities, Rocket Lab has also been developing its own satellite system – Photon – which the company has indicated could also be used as a carrier vehicle for small interplanetary science missions.

In this, CEO Peter Beck has long been a proponent of exploring Venus, and has been contemplating sending a small mission that planet for the last two years – something he believes Rocket Lab could achieve for as little as US $30 million, utilising Electron as the launcher and Photon as the ferry vehicle, delivering a small science probe massing around 37 kg to Venus. With the discovery of phosphine in the planet’s atmosphere (see Space Sunday: phosphine on Venus, test flights and Jupiter), Beck has indicated Rocket Lab may well accelerate these plans.

Rocket Lab has also developed is own satellite – Photon – which it is considering as the carrier for a small science mission to Venus in the wake of the discovery of phosphine in the planet’s atmosphere.  Credit: Rocket Lab

One of the most innovative launch vehicle development companies in the world  – and one of the most valuable in terms of funding – is Relativity Space. The company was founded in 2015 by Tim Ellis, an aerospace engineer who started his career at Blue Origin and who serves as Relativity’s CEO, and Jordan Noone, a former SpaceX engineer, who until recently served as the company’s CTO, although he recently vacated that role in favour of becoming an executive advisor to the company. This pedigree allowed the company to generate US $185.7 million in start-up funding.

Thus far, Relativity Space have yet to launch a vehicle, but they expect to do so in the very near future using their Terran-1 expendable two-stage rocket powered by the Aeon-1 rocket motor. What is particularly noteworthy with both the rocket and its engine is that Relativity produce them  almost entirely via 3D printing in an automated facility (see the animated image at the top of this article to see a Terran-1 fuel tank being built via a 3D laser printer).

Elements of the rocket – fuel tanks, pump systems, etc., – have already undergone extensive prototyping and testing, using both 3D scale model versions and full-size units, and the Aeon-1 has been subjected to numerous test firings. Construction of both the rocket elements and engine parts use proprietary alloys, while the entire 3D manufacturing process massively cuts down on overheads for the company, allowing them to start offering customers launch capabilities of 900 kg to LEO or 700 kg to a 1,200km SSO for just US $12 million a launch from around 2021.

December 19th, 2019, a Relativity Space 3D printed Aeon-1 rocket motor undergoing a full throttle test firing at NASA’s Stennis Space Centre, Mississippi . Credit: Rocket Lab

To  achieve launches, Rocket Lab have leased the use of Launch Complex 16 at Cape Canaveral Air Force Station, Florida, where they have built their own launch support facilities and launch pad. Initial flights from here will be on  behalf of telecommunications provider Iridium, which has contracted Relativity for at least six communication satellite launches. In addition, in June 2020 Relativity announced it had reached a further agreement with the US Air  force to operate polar orbit launches out of Vandenberg Air Force Base, California, from around 2023 onwards.

Pi Planet

A recently discovered exoplanet serves as an unusual (if slightly indirect) illustration of the tie between mathematics and astronomy – and also  has some fun references to baking.

The planet in question has been called K2-315b, and is located some 186 light years from Earth. It is thought to be slightly smaller than our home planet, around 95% the size, something that likely makes it a solid, rocky planet – although this has yet to be confirmed. It  is orbiting a so-called “ultra-cool” star: a stellar body roughly one-fifth the size of the Sun burning at much lower temperatures.

“Pi Planet” orbits its parent star e very 3.14 terrestrial days. Credit: NASA Ames/JPL-Caltech/T. Pyle, Christine Daniloff, MIT

The link to mathematics comes from the planet’s orbit: it takes 3.14 terrestrial days to complete a single passage around its parent  – 3.14 of course being the opening digits of pi (π). However, despite the relatively “cool” temperatures put out by its star (at least in comparison to main sequence stars like the Sun), K2-135b is unlikely to be a habitable world, as it has an estimated average surface temperature of 177º C. This also brings in the first of the humorous links to baking: 177º C is a good temperature for baking a – wait for it – pie.

The planet was first spotted by the now defunct Kepler Space Telescope during the K2 phase of its mission (hence the “K2” element of the planet’s name) and was orbiting the 315th star to be found within the K2 data to have at least one planet orbiting it (hence the “315” part of the title) – which is a shame: there could have been a further serendipity had it been the 314th star found to have a planet.

However,the planet was confirmed via observations by a network of ground-based telescopes called SPECULOOS (a creative acronym for “Search for habitable Planets EClipsing Utra-cOOl Stars”). And this is where the second baking “joke” comes in: Speculoos (or Speculaas in Dutch and spéculoos in French) is a type of spiced shortbread biscuit traditionally baked for consumption on, or just before, St Nicholas’ day.

These baking references, and the link to pi have been reflected in the title of the paper describing the planet, issued by researchers from MIT: π Earth: a 3.14-day Earth-sized Planet from K2’s Kitchen Served Warm by the SPECULOOS Team.

Leaving aside this scientific jocularity, while it is unlikely to be a habitable world, K2-315b is likely to become the subject of intense study, particularly if it is confirmed as having an atmosphere, as its relative proximity to Earth makes it a reasonable candidate for study by the next generations of Earth and space-based telescopes, thus helping us to understand the potential nature and complexities of exoplanet atmospheres.

Solar Cycle 25

As  most of us are aware, the Sun has an activity cycle that is generally 11 years in length (although sometimes it can be longer or shorter) that carries it from periods of relative calm to periods of intense activity, with multiple sunspots marring its surface, accompanied by outbursts such as coronal loops and prominences, solar flares and coronal mass ejections (CMEs).

A group of sunspots, labeled as Active Region 1520 rotated into view over the left side of the sun on July 7, 2012 during Solar Cycle 24. The large spot on the bottom left stretches is 139,200 km across and the full chain of sunspots 320,000 km across. Credit: Alan Friedman

For the last few years, the Sun has been largely and relatively quiescent: there have been relatively few sunspots and little in the way of associated violent behaviour. In fact, solar experts believed the Sun reached its point of absolute minimal sunspot activity in December 2019 – the point that generally marks the end of a cycle, and we’re now into the Sun’s 25th cycle (so called as it is the 25th cycle that has been noted since accurate records of solar activity started to be kept), and over the next several years, we can expect a distinct upswing in solar activity, reaching its peak – the Solar Maximum – in around 2025, before things again start to settled back down through the second half of the cycle. 

There’s no reason to suspect Cycle 25 will be in any way more violent than past recorded periods of Solar Maximum, but the increase in activity is a salient reminder that with a planned return to the Moon scheduled to occur on or around the Cycle 25 Solar Maximum, the risks of things like CMEs to expose missions on the Moon to risks that run from general communications interference through to significant disruption of electrical and electronic systems and increased radiation exposure risks for astronauts.

Overall, Earth and Moon has rarely been affected by a large CME. The last really significant event (in fact,the first to be identified as being link to solar activity) was the Carrington Event of 1859. This was the result of a massive CME that could be indirectly observed from Earth as it extended out from the Sun’s corona. The electrical impact, meanwhile caused widespread disruption in the newly-established United States telegraph network. Reported incidents included telegraph wires becoming so intensely charged that they either blew out the batteries normally used to power them,  giving rise to fires, or gave telegraph operators severe electric shocks. Some operators reported they were able to actually disconnect their systems from their batteries and send and receive messages purely as a result of the charge carried by the wires.

A coronal loop associated with a large CME and made of of denser material that could not escape the Sun’s gravitational and magnet fields, with the Earth rendered beside it for comparison. Credit: NASA / EMSS

Which is not to say we’re not at risk The last solar Cycle resulted in several “near misses” and “glancing blows” from CMEs. The largest of this occurred in July 2012 in what has been called a “solar super storm” that includes a massive CME that, had it fully struck Earth, would have been the modern equivalent of the Carrington Event, powerful enough to disrupt overhead power lines, affect electronic communications systems and even impact things like GPS navigation. As such, the arrival of cycle 25 stands as a subtle reminder as the risks we face in space exploration, and the precautions we must take in efforts to return to the Moon, a place which,takes to its lack of a magnetic field, and more exposed to upset by a large CME.

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