Space Sunday: collisons, rockets, and telescopes

Official poster for the DART mission, a joint NASA-John Hopkins University Applied Physics Laboraroty (JHUAPL) mission. Credit: NASA

Monday, September 26th 2022 will see NASA’s Double Asteroid Redirection Test (DART) reach its primary goal when a small space probe will collide with an asteroid called Dimorphos in an attempt to test a method of planetary defence against near-Earth objects (NEOs) by deflecting their path around the Sun via a kinetic impact.

The risk we face from Earth-crossing NEOs – asteroids and cometary’s fragments that routinely zoom across or graze the Earth’s orbit as they follow their own paths around the Sun – is not insignificant. More that 8,000 of such objects are currently being tracked, and that number is still rising. Such objects range in size from the relatively small to objects like the infamous 99942 Apophis (370m along one axis). which were it to strike Earth, would result in an estimated explosive force equivalent to 1,000 megatons, through to objects large enough to result in possible extinction events.

In 2013, a cometary fragment roughly 20m across entered Earth’s atmpsohere to explode 26km above the the Russian oblast of Chelyabinsk with a force of 400–500 kilotons of TNT. The resulting shockwave damaged some 7,200 buildings and injured over 1,500 people in 6 cities. This image captures the fragment’s path as it burnt up through the denser atmosphere. with the poiint of its explosive destruction marked by a distinctive “mushroom cloud” towards the right-hand end of the trail. Credit: Alex Alishevskikh

Over the years, various means of prevent such an impact have been suggested, with one of the most popular being the use of the kinetic energy from one or more impacts against the threat to alter its orbital track around the Sun so it would miss Earth. It is a popular option because if we get sufficient warning about a threatening object, it should be possible to plan an intercept mission to strike it at a point in its orbit where only a very small deflection in its track would be enough to ensure it misses Earth, allowing smaller, more manageable payloads to be used.

DART is the final incarnation of what started as two independent missions by NASA and the European Space Agency (ESA) to achieve the same goal. These were then combined into a single mission –  AIDA (for Asteroid Impact & Deflection Assessment(, which would have seen ESA launch a observation platform intended to fly to the designated target asteroid and carry out observations and analysis prior to NASA’s DART impactor arriving, and then observing the impact on the latter and the effect it had on the target’s orbit.

However, the ESA element of the mission was cancelled, leaving NASA to push ahead with DART, with the role of observing the impact taken over by Earth-based based observatories and a small payload carried by DART. To compensate, ESA now plans to launch Hera in October 2024, a mission and vehicle that will rendezvous with the target asteroid in 2027 to observe the overall results of the DART mission.

Dimorphos, the target for DART, is actually a relatively small asteroid, some 170m across (but still large enough to result in considerable destruction and loss of life were it to enter Earth’s atmosphere and explode). It has been selected for a combination of reasons, the most pertinent being it is actually the moon of a much larger asteroid, 65803 Didymos (Greek for “twin”), itself a NEO forming part of the Apollo group, and noted as being potentially hazardous to Earth. It is around 780m across, and it orbits the Sun every 770 days, its orbit eccentric enough  for it to cross both the orbits of Earth and Mars, and thus present a potential impact hazard to both.

Dimorphos (Greek: “having two forms” and discovered in 2003, seven years after Didymos was first located) occupies an equatorial and near-circular orbit around Didymos with a period of 11.9 hours. This makes it an attractive target because its position is easy to calculate / track, and the fact that it is orbiting a large object means that the angle of deflection as a result of DART’s impact can be directly measured against its motion around Didymos, and from this it will be possibly to extrapolate the amount of deflection achieved had Dimorphos been a solo asteroid en route to a collision with Earth.

DART launched on November 24th, 2021 atop a Falcon 9 rocket. In order to impact the asteroid at a speed sufficient to affect its velocity, the vehicle has been propelled towards its target by a solar-powered NEXT ion thruster, and will strike Dimorphos head-on at a speed of 6.6 kilometres per second. This should be sufficient to effectively slow it in its orbit around Didymos and result in a charge to the orbital period and shape. Given Dimorphos is large enough to exert some gravitational influence over its parent, it is expected that Didymos’ velocity and orbit will also be affected to a small degree.

An artist’s impression of how the LICIACube cubesat might witness the outflow of ejecta from DART’s impact into Dimorphos. Credit: ESA / Italian Space Agency

Exactly how small or obvious all these changes will be is unknown – we simply do not know the topography of Dimorphos to know where and how DART will strike it. However, to assist with Earth-based observations of the impact, earlier this month DART released the Light Italian CubeSat for Imaging of Asteroids (LICIACube).

Built by the Italian Space Agency, this cubesat is now on a trajectory that will carry it through the Didymos / Dimorphos pairing, allowing it to observe and hopefully record DART’s impact and also gather initial data on the immediate results of the impact – although it is estimated that it will be a week or so before the overall effects of the impact can be properly interpreted. Similar cubesats, originally dubbed “Luke” and “Leia” but now officially called Milani and Juventas (a case of football winning out over Star Wars in the Italian science team?) will accompany the Hera mission in 2024.

DART itself carries little in the way of science instruments related to the mission, other than a 20 cm aperture camera called Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO, which should record and return images of both Didymos and Dimorphos right up to the actual impact). However, it is in many respects also a technology demonstrator, making use of the  Roll Out Solar Array (ROSA) system recently deployed to the International Space Station, and which allows for more efficient harvesting of sunlight over a smaller area of solar array surfaces to generate power, and also RLSA, the spiral Radial Line Slot Array, a new type of compact and lightweight high gain communication antenna.

An artist’s impression of the NASA DART vehicle under propulsive thrust from its ion engine, moments before impacting with the asteroid Dimorphos. Credit: NASA

Currently, DART remains on course for an impact with Dimorphos at 23:14 UTC on Monday, September 26th, 2022. The images returned by the DRACO camera ahead of the impact will mark only the 6th time we have received close-up images of the surface of an asteroid.

Big Boosters: SpaceX Booster 7’s Seven and Artemis 1’s Weather Delay

It’s been a week of ups and downs for the two big boosters which are most prominently on spaceflight enthusiasts’ minds.

At the SpaceX Starbase Facility in Boca Chica, Texas, Booster 7, the vehicle seen as the favourite to lift the company’s massive Starship into the sky on the system’s first orbital attempt, completed a second spin-start test of seven of its 33 Raptor 2 engines  on September 19th. This looked to be a different selection of motors to those tested the previous week, meaning that between 14 and 17 of the booster’s motors have now completed spin-starts. Nor was this the end of things: just a few hours after the spin-start – which lasted around 13 seconds – the booster was re-pressurised with fuel and warning given of a further engine test.

This was a full static fire of seven of the engines, marking the largest number of Raptor 2 motors to go through such a test thus far. Slow-motion payback of high-speed film shot of the event reveals that – as with the spin-start tests – rather than igniting all seven engines simultaneously, engine ignition was staggered, which might be indicative of how actual orbital launches will be managed; staggering engine starts by just a few milliseconds could help with reducing noise vibration resulting from all 33 engines coughing into life at the same time, and may even help reduce the amount of sound being deflected back up against the vehicle and the launch stand.

Following this test, SpaceX announced that, rather than remaining at the orbital launch facility for further engine tests, Booster 7 would be returned to the production centre at Starbase for “robustness upgrades”, and Booster 8 would replace it on the orbital launch mount to undergo its own testing. Whilst not entirely clear from the tweets given, it appears these tests will include a full wet dress rehearsal (WDR), which could involve stacking the booster with Starship 24, then fully tanking them and proceeding through a launch countdown that stops short of engine ignition. Then, after this, there will be a full 33-motor static fire test for a booster.

Whether this means Booster 8 will overtake Booster 7 to become the vehicle to make the first orbital launch attempt with a Starship on top, or whether the two boosters will again be swapped to allow Booster 7 make the attempt – which SpaceX appear to be hoping to make in November (still subject to the granting of an FAA license) – is unclear.

Either way, Booster 7 was removed from the launch mount mid-week, and the launch mount itself then went through a series of tests of its upgraded sound suppression system, which appears to deliver both water and nitrogen as to the flame pit of the launch table to both absorb sound (and reduce the potential for it causing damage to the vehicle or launch facilities) and reduce the risk of unexpected fire.

Booster 8 (centre left) imaged on Highway 4, Boca Chica, on its way to the Starbase test and launch facilities. Just to the right of the booster stands Starship 24, located on a sub-orbital test stand. Centred in the photo is the orbtial launch tower, with the mechazilla lifting arms lowered and rotated away from the launch table and Booster 7 (hidden by the bulk of the launch tower). Credit: (not a NASA afilliate)
Meanwhile, on September 21st, NASA held a further fuelling test of the massive Space launch System rocket that will launch the uncrewed Artemis 1 mission to cislunar space. Earlier attempts to complete this test – a critical final step in readying the massive launcher for its maiden flight – had to be curtailed due to leaks in the liquid hydrogen fuel feed system at the base of the rocket, leading to padside repairs, as I noted in my previous Space Sunday update.

While the September 21st test also encountered leaks with the liquid hydrogen propellant flow, they were now sufficient to curtail operations, and the tst was successfully completed with both the core and upper stage liquid oxygen and liquid hydrogen tanks being fully fuelled roughly 6 hours after operations commenced.

One September 23rd, and after post-test checks on the vehicle, NASA held a press conference to confirm they would be making a launch attempt on Tuesday, September 27th, 2022 – only to have to call off the attempt on the 24th September due to tropical storm Ian threatening to roll across Florida and over the Space Coast, potentially requiring the vehicle to be rolled back to the safety of the Vehicle Assembly Building (VAB).

The Artemis 1 SLS booster on launch pad 39-B at Kennedy Space Centre. Credit: NASA

At the time of writing, no final decision had been announced regarding the roll-back proceeding. Should it occur, it is likely to occur overnight (local time) on Sunday 25th / Monday 26th September). This roll-back would mean the earliest launch opportunity would be October 2nd; however, this is a date in doubt due to the planned October 3rd launch for the NASA / SpaceX Crew 5 mission to the ISS from neighbouring Pad 39A. As both pads within launch Complex 39 at Kennedy Space Centre use the same infrastructure, back-to-back launches from the two pads are logistically difficult, and was there are further windows for the Artemis 1 launch, letting this slip is seen as preferrable to disrupting ISS operations.

The one good piece of news for Artemis 1, is that the flight termination system (FTS) has received a recertification waiver from the US Space Command at Cape Canaveral Space Centre. The FTS is used to destroy a rocket should it veer off-course post-launch. However, its batteries have a limited service life, and so packages need routine re-certification to state their batteries are suitable for use – or the batteries require replcing. Re-certification  / replacement means returning the vehicle to at VAB, further delaying any launch. However, the USSC has agreed that the package on the SLS could have the recertification delayed until mid-October, allowing the vehicle o be available for the late September / early October launch windows.

JWST Update: Images and Issues

On September 24th, NASA released images of the solar system’s outermost planet, as captured by the James Web Space Telescope. The pictures, taken in July 2022, show not only Neptune’s thin rings, but its faint dust bands, never before observed in the infrared, as well as seven of its 14 known moons.

Neptune, its rings and some of its moons as seen by JWST in July 2022. Credit: NASA

Neptune has fascinated researchers since its discovery in 1846. Located 30 times farther from the Sun than Earth, it is characterised as an ice giant due to the chemical make-up of its interior, whilse because of the great amounts of methane and heavier elements within its atmosphere, it has a disntinctive ocean blue colouring when seen in visible light.

The JWST images capture Neptune in the near-infra-red wavelengths which are readily absorbed by the planet’s atmosphere. This results in it appearing very differently to how it appears in visible light, looking light a misty, crystal marble lit from within by bright streaks – actually the atmospheric interactions only previously hited at b the passge of high-althitude cloud zipping around the planet. Beyond it, and more particularly, the planet’s ring and dust system is revealed in the clearest detail seen in more than 30 years.

Three views of Neptune over the decades, each revealing different information about the planet and its rings. Credit: NASA

Among the seven moons also captured in the JWST images is massive Triton, which appears to float over Neptune like a giant star – the result of the moon reflecting around 70% of the sunlight striking it, thanks to the frozen sheen of condensed nitrogen covering it.

The images of Neptune came at a time when it was confirmed the observatory has developed a minor issue. This lays with a grating wheel mechanism within the Mid-Infrared Instrument (MIRI), resulting in suspension of one of the instrument’s four operating modes (medium-resolution spectroscopy observations).  The other three observing modes — imaging, low-resolution spectroscopy and coronagraphy — are not affected, and observations using those modes of MIRI are continuing.

Naptune and its rings and moons, as omaged by JWST in July 2022. Credit: NASA

The cause of the friction within the mechanism is not clear. Hoever, NASA made it clear the decision to suspend the affected operations with MIRI was not as a result of failure, but rather “an abundance of caution” so that engineers could review telemetry data from the instrument and the mechanism in order to understand the extent of the issue, what might be done to correct it and the potential for impact on mid-range spectroscopy data already gathered by the instrument. In the meantime, mission managers remain confident MIRI will return to full operations in the near future.

Space Sunday: the Sun, Moon and updates

An artist’s impression of a ustaining Lunar Development (SLD) lander heading for the Moon (see below). Credit: NASA

The launch of Artemis 1, provisionally scheduled for September 23rd has been … postponed,  just days after NASA indicated the date was their preferred new target for the uncrewed mission to cislunar space.

As I noted in my previous Space Sunday update, this date and the one following it (September 27th 2022), hinged on a number of factors, including a test of the repaired propellant feed lines on the mobile launch platform which have proven to be the thorn in NASA’s paw when it comes to the first launch of the massive Space Launch System rocket.

This test had been scheduled for Saturday, September 17th. However, it was decided to push it back to the 21st to allow more time for the ground crew to have more time to prepare for the load test. Attention has therefore switched to attempting the launch on September 27th with October 2nd a provisional back-up date. However, the latter remains under review as NASA plan to launch a crew to the International Space Station (ISS) aboard the SpaceX Crew 5 Falcon 9 / Crew Dragon combination from Pad 39A on October 3rd.

Artemis 1 on pad 39B at Kennedy Space Centre: no launch before September 27th, 2022. Credit: NASA/Joel Kowsky

A further potential hurdle for meeting either launch date is the need for the US Space Force to grant a waiver on the recertification of the Flight Termination System (FTS) – the package used to remotely destroy the rocket if it veers off-course during its ascent through the atmosphere. The request for a waiver is still being evaluated at Canaveral Space Force station; if denied, then the rocket will have to be rolled back to the Vehicle Assembly Building (VAB) so the FTS can be fully re-certified – a porcess that is liable to push any launch back until after October 2nd.

The September 27th launch window opens at 15:37 UTC for 70 minutes and presents a “long class” mission for the uncrewed Orion space vehicle, lasting 41 days, with splashdown occurring on November 5th, off the coast of San Diego, California.

NASA Requests Proposals for Additional Lunar Landers

On September 16th, NASA issued a call for proposals for a lunar lander vehicle in support for crewed lunar missions beyond the initial Artemis 3 mission – the first mission to land an American crew on the Moon since 1972’s Apollo 17 mission.

That first mission is due to utilise a modified version of SpaceX’s Starship for place a crew of two on the surface of the Moon and return them to orbit. However, the contract granted to SpaceX – which has yet to actually proceed with work on the modified vehicle in earnest – was viewed as controversial at the time it was given, being granted in the face of two far more capable – if more expensive – proposals. As a result, NASA was ordered by Congress to seek an additional lander vehicle under what is referred to as the Sustaining Lunar Development (SLD) project. Companies interested in responding to the call have until November 15th, 2022 to do so.

The call is for a far more versatile vehicle than that defined by the contract for the initial Human Landing System (HLS) contract awarded to SpaceX. It calls for a lander vehicle type capable of “sortie” style missions with crews of 2 and landing up to 25 days apiece, with the crew living aboard the vehicle. These missions will likely be “scout missions” to evaluate potential sites on the Moon where a base might be established.

The NASA NextStep HLS-SLD includes the development of the lunar gateway station orbiting the Moon and stratgies for carrying technologies developed for lunar operations for use on Mars. Credit: NASA

In addition, and supported by habitat units delivered separately to the lunar surface, the vehicle must be capable of landing crews of 4 astronauts on the Moon for up to 33 days at a time. Finally the vehicle design must be capable of automated cargo landings on the Moon in support of crewed missions.

It is not currently clear whether the two completing proposals for the original HLS contract – led respectively by Blue Origin and Dynetics – will participate in submitting proposals. Two of Blue Origin’s partners for the original HLS contract, Lockheed Martin and Northrop Grumman, have remained non-committal towards further participation in any additional lander projects since the SLD project was formally announced in March 2022.

Dynetics, however, were one of five companies to receive US $40.8 million each from NASA as a part of a 15-month initial SLD study initated in September 2021. As  a part of this work, Dynetics committed to risk-reduction activities and provide feedback on NASA’s requirements to cultivate industry capabilities for crewed lunar landing missions. Of the three original HLS  proposals, the Dynetics design – whilst the most expensive – most closely matched the requirements outlined in the SLD call and offered the advantage of being launched to the Moon using vehicles other than SLS. As such, there is some speculation they will respond to this new call for proposals.

An artist’s concept of the Dynetic’s HLS lander, originally rejected by NASA. Credit: Dynetics

SpaceX is excluded from responding to this new call for proposal. However, NASA indicating it plans to exercise an option in SpaceX’s existing contract and call on SpaceX to evolve is lunar Starship design “to meet an extended set of requirements for sustaining missions at the moon and conduct another crewed demonstration landing.”

Continue reading “Space Sunday: the Sun, Moon and updates”

Space Sunday: JWST, Artemis, DKIST and starship

Caught by the NIRCam on the James Webb Space Telescope, this image reveals the details at the very heart of 30 Doradus. Credit: NASA / ESA

The above image is of a region of space officially called 30 Doradus, located in the south-east corner (from Earth’s perspective) of the Large Magellanic Cloud (LMC), one of the “satellite” galaxies to our own.

Known more familiarly as the Tarantula Nebula, the region has long been a subject for study by astronomers as it is the largest and brightest star-forming group in our local group of galaxies. Its popular name originates in the way the dusty filaments within it suggest the web found within the holes of burrowing tarantulas, the black “holes” within the suggesting the spider lying in wait in its hide, ready to pounce on any prey passing by.

Even though it and other nebulae have been imaged many times over the years, the Tarantula and its cousins still contain many secrets about the processes involved in the formation of stars. As such, they remain targets of considerable interest to astronomers, and the these images, captured by the Near-Infrared Camera (NIRCam) and processed by the Near-Infrared Spectrograph (NIRSpec), and also by the Mid-infrared Instrument (MIRI) on the James Webb Space Telescope (JWST), reveal the Tarantula Nebula in never-before seen details.

A mosaic view of 30 Doradus, assembled from Hubble Space Telescope photos, The focus of the JWST image is the smaller of the two dark areas within the nebula. Credit: NASA, ESA, ESO.

Visible in depth for the very first time are thousands of young stars, distant background galaxies, and the detailed structure of the nebula’s gas and dust formations as they are pushed, pulled and twisted by the solar winds within the nebula. Such is the unprecedented power of Webb’s imaging systems; it was even able to capture one young star in the act of shedding a cloud of dust from around itself, dust which may eventually form one or more planets orbiting the star.

Processing of the images by (NIRCam), combined with the NIRSpec data show that the cavity at the centre of the nebula is the result of powerful solar winds radiating outwards from a cluster of massive young stars, which appear as pale blue dots.

Only the densest surrounding areas of the nebula resist erosion by these stars’ powerful stellar winds, forming pillars that appear to point back toward the cluster. These pillars contain forming protostars, which will eventually emerge from their dusty cocoons and take their turn shaping the nebula.

– Part of a statement on the Tarantula Nebula image by the JWST imaging team

This image is one of the most recent to the published from the cache JWST has already gathered and transmitted back to Earth – but it is not among the more recent to be received. Ironically, despite its beauty, it was one of those received following the telescope completing its commissioning and starting formal science operations. However, it was passed over as one of the images to be selected for the very first release of JWST images back in July on the ground NASA / ESA had “more interesting” subjects to be included in the initial release and press conference!

Artemis Update

Following the September 3rd launch attempt scrub for the Artmis-1 mission, featuring NASA’s new Space Launch System, engineers have been hard at work. The scrub was the result of a significant liquid hydrogen leak during the propellant loading process, and following the scrub, it was unclear as to whether the rocket would be rolled back to the Vehicle Assembly Building (VAB) for repairs or an attempt would be made to fix matters on the pad.

On September 6th, the decision was made to try the latter, and would focus on replacing the seal on the 20-cm liquid hydrogen feed within the quick disconnect system that connects the propellant feeds from the mobile launch platform to the rocket. Work on replacing the seal commenced on September 8th, and was successfully concluded on September 9th.

The Base of the Artemis 1 SLS rocket on the mobile launch platform at Pad-39B,  Kennedy Space Centre. To the left is the quick disconnect system with its protective rocker cover. It was the seals at the end of the pipes connecting this to the rocket which failed to prevent liquid hydrogen leaks during propellant loading. Credit: NASA

At the same time, a smaller 10-cm bleed valve located between the rocket’s core and upper stage was also replaced as a precautionary repair; this valve refused to obey ground instructions when engineers were trying to use an overpressure of the liquid hydrogen pipe to try and force the feed seal to work. With both repairs successfully completed, NASA looked towards possible dates for a third launch attempt, settling on either September 23rd or September 27th.However, these are dependent on a couple of significant requirements.

The first is a fuelling test designed to ensure the propellant feeds are now working correctly, and will involve loading both liquid hydrogen and liquid oxygen in a revised propellant loading process. This will take place on September 17th and will involve loading the tanks of both the core stage and the upper stage of the SLS. This test will also be used to perform a “kick-start bleed test” on the SLS rocket’s four main engines. That test is designed to chill the engines down to a temperature of -251º Celsius) to prepare them for their super-chilled propellant during a launch.

The second requirement is the granting of a waiver by the U.S. Space Force for the vehicle’s flight termination system (FTS). This is the package designed to destroy the rocket if it veers off course during launch. Powered by batteries, the FTS needs periodic checks, and the current certification period ended on September 6th. Therefore is the USSF do not agree to a waiver, the SLS will need to be rolled back to the Vehicle Assembly Building in order for the FTS packages to be inspected, and possibly replaced; all of which would mean missing the September launch dates.

A close-up of the base of the SLS rocket, showing engineers working on the quick disconnect system, demonstrating the sheer scale of the rocker and its boosters. Credit: NASA

If Artemis 1 were to launch on September 23rd, it will be on a so-called “short class” mission lasting 26 days, with splashdown on October 18th. However, if the 27th launch date is used, it would mark a “long class” mission, with splashdown not occurring until November 5th for total mission duration of 41 days.

Prior to the repair attempt on the Artemis 1 SLS, NASA announced the contract for the Artemis space suits due to be used with the Artemis 3 mission and the first lunar landing for the programme.

As I’ve previously noted, the development of an entirely new space suit NASA could use to replace the current suits – themselves based on the Apollo design started in 2007. however, development was riddled with issues to the point where even after a “final” design was announced, NASA’s own Office of Inspector General (OIG) rated it as unsuitable and unlikely to be ready for the then-planned 2025 lunar landing of Artemis 3 (see: Space Sunday: Mars, Starliner woes, accusations & spacesuits).

Because of this, earlier in 2022, NASA turned to Axiom Space – who are already engaged in space station activities; and to Collins Aerospace + ILC Dover – a team that has decades of experience with the current EVA suits used by NASA – and offered them the opportunity to put forward initial designs for a new EVA suit,  with potential to gain a US $3.4 billion contract to supply NASA with suits through until 2035.

That contract has now – somewhat surprisingly, given the track record Collins / ILC Collins have in space suit design – gone to Axiom, who will supply NASA with a “moonwalking system” of suits and support systems to be used as a part of the Artemis programme, starting with Artemis 3. Neither NASA nor Axiom have been particularly forthcoming as to why the latter was chosen, and few details on their suit – outside of a partial image and the idea that it will be “evolvable”  – have been provided.

The only image available of the new lunar space suit to be developed by Axiom Space for NASA. Credit: Axiom Space

By contrast, and prior to the announcement, Collins / ILC Denver presented concepts of their suit designs, and opened a new facility for suit development and construction on August 31st.

However, documentation suggests that pricing has been a major consideration: Axiom’s pricing is said to have been some 23% below NASA’s cost estimate for suit development, and Collins / ILC Dover’s pricing was just 2% below the estimate – which may actually reflect a more realistic estimate for suit development.

Continue reading “Space Sunday: JWST, Artemis, DKIST and starship”

Space Sunday: equations and launch scrubs

Dr. Frank Drake and his equation

Anyone with a reasonable interest in astronomy will recognise the above image as containing the Drake Equation, sometimes referred to as “the second most famous equation after E=Mc2

It was first proposed in 1961 by American astronomer and astronomer and astrophysicist Dr. Frank Drake as a probabilistic argument to estimate the number of active, communicative extraterrestrial civilisations in the Milky Way Galaxy. Its values are defined as:

N = the number of civilisations in our galaxy with which communication might be possible (i.e. which are on our current past light cone);


R = the average rate of star formation in our Galaxy.

fp = the fraction of those stars that have planets.

ne = the average number of planets that can potentially support life per star that has planets.

fl = the fraction of planets that could support life that actually develop life at some point.

fi = the fraction of planets with life that actually go on to develop intelligent life (civilisations).

fc = the fraction of civilisations that develop a technology that releases detectable signs of their existence into space.

L = the length of time for which such civilizations release detectable signals into space.

In the decades since its initial publication, the Drake Equation has been widely critiqued by astronomers and mathematicians because the estimated values for several of its factors are highly conjectural  such being that the uncertainty associated with any of them so large, the equation cannot be used to draw firm conclusions.

However, these critiques actually miss the point behind Drake formulating the equation in the first place, because he was not attempting to quantify the number of extra-solar civilisations which might exist, but rather as a way to stimulate scientific dialogue about what had been very much looked upon as an outlier of research, and to help formulate constructive discussion on what is regarded on the first formalised discussion on the search for extra-terrestrial intelligence (SETI), as he noted in his memoirs:

As I planned the meeting, I realised a few day[s] ahead of time we needed an agenda. And so I wrote down all the things you needed to know to predict how hard it’s going to be to detect extra-terrestrial life. And looking at them it became pretty evident that if you multiplied all these together, you got a number, N, which is the number of detectable civilizations in our galaxy. This was aimed at the radio search, and not to search for primordial or primitive life forms.

– Frank Drake

Frank Drake not only hosted the first US meeting to discuss the potential for seeking signs of possible extra-terrestrial civilisations, he pioneered several of the earliest attempts to seek any such signals as demonstrating methods that might be used as a means to intentionally communicate our existence to other civilisations within the galaxy. As such, his work did much to put our speculative thinking about intelligences elsewhere in the galaxy on a solid foundation of scientific research, as will as being responsible for some for the foremost research in the field of modern radio astronomy.

This is his story.

Born in Chicago on May 28th, 1930, Frank Drake was drawn to the sciences and to electronics from an early age, and in order to further his education in both, he enlisted in the US Navy Reserve Officer Training Corps (ROTC).  This allowed him to obtain a scholarship at the prestigious Cornell University, ostensibly to obtain qualifications in electronics, but also study astronomy.

While at Cornell, Drake’s astronomy class were able to attend a lecture by astrophysicist Otto Struve. While his name may not be instantly recognised, Struve was one of the most distinguished astronomers of the mid-20th century, a member of a generational family of astronomers stretching by to the 18th century and Friedrich Georg Wilhelm von Struve. He was also one of the first astronomers to openly promote radio astronomy as a key to determining whether there might be other intelligences living in our galaxy – an idea his contemporaries tolerated, rather than embraced.

Struve’s presentation positively affected Drake, and following his required 1-year military service following graduation in 1951 (served as the Electronics Officer aboard the cruiser USS Albany), Drake enrolled at Harvard University, where gained his doctorate in astronomy, with a focus on radio astronomy.

Frank Drake in one of his official portraits at Green Bank observatory (1962). Credit: Green Bank

In 1956 Otto Struve was appointed as the first director of the National Radio Astronomy Observatory (NRAO)), and he started overseeing the establishment of a number of national radio astronomy centres across the United States. One of these was at Green Bank, Virginia, a facility Drake joined as a researcher in 1958. His initial work here started with the static arrays at Green Bank, carrying out the first ever mapping of the centre of the Milky Way galaxy, and the discovering that Jupiter has both an ionosphere and magnetosphere.

However, Struve was keen to enhance the facilities with steerable radio dishes, and to this end purchased an “off-the-shelf” 26 m dish and had engineer Edward Tatel (for whom it was later named) design a motorised mount for it so it could be pointed around the sky. This work was completed in 1959, and Struve turned to Drake to formulate the telescope’s first science mission.

At the time, Drake had just read an intriguing article in Nature magazine entitled Searching for Interstellar Communications. Within it, physicists Giuseppe Cocconi and Philip Morrison proposed using a large radio dish to monitor “incoming” radiation from stars along the 21-cm / 1,420.4 MHz wavelength – the radio frequency used by neutral hydrogen.  Given this is the most common element in the universe, Cocconi and Morrison speculated it would be logical landmark in the radio spectrum to manipulate as a message carrier.

Taking this idea, Drake developed Project Ozma, a three-month programme run at the start of 1960 to listen for any signals coming from the vicinity of either Tau Ceti or Epsilon Eridani. At the time, no-one knew if either star fielded planets (although both were found have at least one planet orbiting them almost 50 years after Drake’s experiment).

Frank Drake in front of the 85-1 (Tatel) Telescope. the first steerable telescope built at NRO Green Bank (and now one of 3 such telescopes, collectively referred to as the Green Bank Interferometer), used in Drake’s first SETI experiment, Project Ozma. Credit: NRAO Green Bank

Following Ozma, Drake was encouraged to formalise SETI research into a more co-ordinated effort (various programmes, such as Ohio State University’s work using the Big Ear telescope, were already in existence but without any real coordination). To this end, he helped put together the first small-scale meeting / conference on the subject in 1961 – the event at which he used his equation to  stimulate the discussion.

Among those attending were Otto Struve (now retired), Phillip Morrison, astronomers Carl Sagan and Su-Shu Huang, chemist Melvin Calvin, neuroscientist John C. Lilly, and inventor Barney Oliver. Together they called themselves The Order of the Dolphin (due to  Lilly’s work on dolphin communications), and together they laid the groundwork for a systematic approach to SETI research, which over the coming years would in turn give birth to numerous programmes, and more fully legitimise such research within scientific circles.

In the mid-1960s, and still based at Green Bank, Drake was nominated to spearhead converting the massive Arecibo Ionosphere Observatory  – originally built as a project to study the Earth’s ionosphere as a means of detecting nuclear warheads inbound towards the United States – into what would become more famously known as the Arecibo Observatory, for several decades the largest radio telescope in the world.

This work finished in 1969 when the National Science Foundation formally took over the Arecibo faculties, and two years later Drake was approached by Carl Sagan with another intriguing proposal. Sagan had himself been approached English journalist Eric Burgess – who at the time was writing about the upcoming NASA Pioneer 10 and Pioneer 11  missions – about the idea of sending a physical message out to the stars.

Continue reading “Space Sunday: equations and launch scrubs”

Space Sunday: “we are go for launch” – Artemis 1 on the pad

Backlit by the setting Sun illuminating rainclouds, NASA’s Artemis-1 Space Launch System rocket sits on launch pad £9B at NASA’s Kennedy Space Centre, August 26th, 2022. Credit: ESA

If all continues on track, Monday, August 29th, 2022 will mark the start of America’s return to the Moon with crewed missions, just a few months shy of the 50th anniversary of the last crewed mission, Apollo 17 (December 7th-19th, 1972). It will come with the lift-off of the Artemis 1 mission, and the maiden flight of NASA’s new heavy lift launcher, the Space Launch System.

The mission will be – as most no doubtless know only too well – uncrewed, and the destination not the lunar surface, but cislunar space in what will be the most comprehensive test of the SLS rocket and the Orion Multi-Purpose Crew Vehicle (MPCV) ahead of crewed flights, which are due to commence with Artemis 2.

The final countdown for the launch commenced on Saturday, August 27th at launch pad 39B within the Kennedy Space Centre, Florida, and providing no significant hitches occur, it is due to terminate at 12:33 UTC on August 29th with the ignition of the booster’s four RS-25 shuttle-derived motors and two massive solid rocket boosters (also derived from those used in the space shuttle programme). At the time of writing this piece, and despite a thunderstorm leading to a lighting strike at the launch facility on the evening of August 27th, everything was on course for the launch, and the forecast indicated a 70% likelihood that the weather at Cape Canaveral and downrange from the launch pad would be good for the launch.

Artemis 1 SLS in Pad 39B at Kennedy Space Centre, imaged from orbit by one of the Maxar constellation of Earth-imaging satellites on August 25th, 2022. Credit: Maxar Technologies

However, all things are not guaranteed, and the mission has a slim 2-hour launch window in which to get off the pad. Should the launch have to be scrubbed for any reason, further launch windows will be available on September 2nd (2 hours), and September 5th (90 minutes).

There is a lot riding on this mission; while Orion has already flown once in space – eight years ago in the uncrewed Exploration Flight Test-1, launched atop a Delta IV Heavy rocket – this will be the first flight of the vehicle outside of directly orbiting the Earth; however, for SLS, the mission could very much be make-or-break. The vehicle has been beset by issues throughout its development programme (many of which amounted to either unforced errors or came as a result of the entire Artemis programme being unduly accelerated by the Trump Administration to achieve a crewed landing by 2024 rather than 2028, as originally planned. As such any major or catastrophic failure could have major repercussions for NASA and the US government space programme.

SLS has been more than two decades in development. It started life in the early 2000s as the Ares V under NASA’s Constellation programme. Instigated by the then NASA administrator Michael Griffin, Ares 5 was to be the heavy-lift launch vehicle intended to help return humans to the Moon and (eventually / primarily) help pave the way to Mars, working alongside the smaller Ares 1 crew launch vehicle and what was then called the Orion Crew Exploration Vehicle (CEV). I say “primarily”, because Griffin was a strong advocate of human missions to Mars and the Ares programme was actually named for (and pretty much lifted from) the Mars Direct humans-to-Mars concept first proposed by Robert Zubrin and David Baker  in 1990.

Despite enormous strides made in the development of Ares 1 (the first of which actually few in 2009) and the Orion CEV, the Obama administration opted to scrap the constellation programme on the grounds of cost. While Ares 1 went away in its entirety, Orion and Ares V underwent a redesign process, the former having its capabilities increased, whist Ares V went back to the drawing board to later emerge as the SLS.

SLS development: on the left, the Block 1 with ICPS that will fly Artemis Mission 1-3.  Centre left: the Black 1B  EUS crew variant to flay Artemis 4-5(+). One the right, the proposed Block 1B and Block 2 cargo variants, that latter of which most closely resembles the Ares V Credit: NASA

The key differences between Ares V and SLS is the former was intended to be a heavy-lift cargo launcher, capable of delivering up to 168 tonnes to low-Earth orbit (LEO), up to 71 tonnes to lunar orbit and around 60 tonnes to Mars, with Ares 1 left to carry crews up to orbit. SLS, on the other hand is intended to be both a crewed and cargo launch vehicle, capable of delivering between 95 and 130 tonnes to LEO depending on the vehicle type, or some 46 tonnes to lunar orbit (Block 2 cargo) and 30-40 tonnes to Mars (Block 2 cargo).

The primary objectives for Artemis 1 are to prove the SLS launch system’s Block 1 launch capabilities; achieve a distant retrograde orbit (DRO) around the Moon, and make a safe return to Earth with a successful atmospheric re-entry and splashdown by the Orion MPCV capsule. The overall mission duration is expected to be some 42 days.

This first flight – which will also mark the first use of the European-built Orion service module (Orion’s flight in 2014 didn’t require a service module) – is to be one of only three launches of the SLS Block 1 rocket. This uses what is called the  Interim Cryogenic Propulsion Stage (ICPS) – essentially the upper stage of a Delta IV rocket. From Artemis 4 onwards, launches will use the more powerful Exploration Upper Stage (EUS) in what is termed the Block 1B SLS variant, and which will also be used in the Block 2 cargo variant (if this eventually flies).

The ICPS will be used to insert Orion into its trajectory to the Moon prior to separating from the capsule and its service module and performing one further crucial mission task. It will then pretty much parallel Orion to the Moon before using the latter’s gravity to slingshot itself away into a highly elliptical orbit of its own.

The flight of Artemis 1 as depicted in the mission’s Press Pack. The mission phase durations are variable to account for the different possible launch dates at the time the pack was published. Credit: NASA (click for full size)

As well as being used to check-out SLS and Orion, Artemis 1 has a number of science goals, and the Orion MPCV is not the only payload for the mission. Shortly after Orion separates from the ICPS, the latter – in that other crucial aspect of the mission mentioned above – will deploy multiple cubesats on trajectories to the Moon. These will carry out an range of scientific tasks, including:

  • Detecting, measuring, and comparing the impact of deep space radiation on living organisms (yeast in this instance) over long durations.
  • Studying the dynamic particles and magnetic fields that stream from the Sun and as a proof of concept for the feasibility of a network of stations to track space weather.
  • Imaging Earth’s plasmasphere to study the radiation environment around the Earth.
  • Searching for additional evidence of lunar water ice from a low lunar orbit.
  • Mapping hydrogen within craters near the lunar south pole, tracking depth and distribution of hydrogen-rich compounds like water over a 60-day, 141 lunar orbit mission.
  • Flying by the Moon to collect surface spectroscopy and thermograph and return the results to Earth for analysis.

In addition, some of the cubesat missions will be technology demonstrators, including a further solar sail demonstrator; using very small automated vehicles to operate in close proximity to large vehicles and image them / look for potential damage; using small, low thrust gas motors for trajectory control in the space between Earth and the Moon.

Nor is that all; Orion itself will be carrying a number of experiments within the capsule, with a focus on gaining a better understanding of the radiation regime between the Earth and Moon and within cislunar space.

The most evident of the onboard experiments is “Commander Moonikin Campos”, a mannequin dressed in the Orion Crew Survival System Suit. Sharing (OCSSS).  Sharing same iconic orange colour as the survival suits used on shuttle missions, the OCSSS is a much more advanced version, designed to be worn continuously for periods of up to 6 days at a time (so whilst en route to the Moon, whilst in lunar orbit and during a return to Earth), to offer enhanced radiation protection for the wearer whilst aboard Orion. To this end the mannequin – named for Apollo 13 electrical subsystems engineer Arturo Campos, who played a major role in bringing that crew back to Earth alive – is equipped with a plethora of radiation sensors to test the effectiveness of the suit.

Continue reading “Space Sunday: “we are go for launch” – Artemis 1 on the pad”

Space Sunday: Voyager at 45

Voyager: 45 years on. Credit: NASA

August and September 2022 mark the 45th anniversaries of the launches of Voyager 1 and Voyager 2, NASA’s twin interplanetary – and now interstellar – explorers.

Designed to take advantages of a planetary alignment which occurs once every 176 years, allowing the use the gravities of one of the outer planets to “slingshot” a vehicle on to the next, the two Voyager mission vehicles remain in operation today, and continue to stand at the forefront of our understanding of the local space surrounding our solar system.

Voyager 1 continues to set records as the furthest man-made object from Earth – it is now over 23.3 billion kilometres away – whilst Voyager 2 remains famous for giving us our first detailed views of Uranus and Neptune during its 20-year voyage through the outer solar system.

Products of the 1970s, the Voyager craft stand as museum pieces by today’s standards. Each has around 23 million times less memory than a modern cellphone, their communications systems can only transmit and receive data some 38,000 times slower than a modern cellular network, and they record the data they gather on an 8-track tape recorder prior to transmitting it back to Earth. Nevertheless, the amount of knowledge they have gathered and returned to us about the outer reaches of the solar system, the heliosphere (the bubble of space around the Sun in which the solar system resides), the heliopause (the boundary between that Sun-dominated “bubble” and the galaxy at large) and the realm of interstellar space beyond that bubble.

Operated by NASA’s Jet Propulsion Laboratory (JPL), the Voyager craft were launched in reverse order, with Voyager 2 lifting-off on August 20th, 1977 and Voyager 1 following on September 5th, 1977. The reason for this ordering was simple: during the development of the mission, Saturn’s moon Titan, known to have an atmosphere, was identified as a primary target for fly-by investigation, and so was assigned to Voyager 1.

Animation of Voyager 1’s trajectory around Jupiter: Pink – Voyager 1; Light Blue · Jupiter; Red · Io; Dark Blue -Europa; Yellow – Ganymede; Green · Callisto. Credit: Phoenix777

However, in order to reach the moon, the vehicle would have to follow a course that would carry it over Saturn’s northern reaches, and throw it “down” and out of the plane of the ecliptic and away from any chance of reaching the outer planets. Instead, Voyager 2 was tasked with completing the “grand tour” of the major planets – Jupiter, Saturn, Uranus and Neptune, and in order to achieve this, it would have to be launched first.

Even so, thanks to the nature of orbital mechanics requiring Voyager 2 to be thrown out on a more circular, “indirect” path towards Jupiter whilst Voyager 1 could be launched more directly towards Jupiter meant it could reach the gas giant first, arriving in January 1979, having “overtaken” Voyager 2 in December 1977. . Its passage through the Jovian system revolutionised our appreciation of the Galilean moons of the system, after which it travelled on to its November 1980 encounter with Saturn and then Titan.

Voyager 2’s more circular trajectory meant it did not reach Jupiter until July 1979, six months behind Voyager 1, but its route allowed it to make a much closer fly-by of Europa, the ice-covered Galilean moon, giving scientists the first hint of the nature of the mechanisms at work deep within the moon.

A transit of Io across Jupiter as imaged by Voyager 2 in July 2022. Credit: NASA/JPL

From here the vehicle journeyed on to an August 1981 encounter with Saturn and then Uranus in 1986 and then Neptune in August 1989, whilst Voyager 1 continued onwards toward the heliopause, all of which I covered in  Space Sunday: Voyager at 40.

In 2010, Voyager 1 commenced a two-year transition from the space dominated by the Sun and its outward flow of radiation, and the realm of interstellar space. The first indications that it was beyond the influence of the Sun’s radiation came in later 2012 – although it was not until March 2013 that this was empirically confirmed through analysis of multiple data returned by the vehicle.

Voyager 2 commenced its voyage through the heliopause in 2013; however, as it was still travelling within the plane of the ecliptic, it was effectively travelling through a “thicker” part of the “bubble wall” of the heliosphere, so it did not enter interstellar space until November 2018.

Even so, and possibly confusingly, neither craft have actually departed the solar system per se. This is because the “size” of the solar system is measured in two ways: the influence of the Sun’s outward flow of radiation and by the influence of its. Despite having passed through the former, both craft are sill within space affected by the latter, and neither will reach the Oort Cloud – the source region of long-period comets and seen as marking the outer limits of the Sun’s gravitational influence – for another 300 years.

As such, both of the nuclear-powered vehicles are now engaged in a multi-vehicle mission (having been joined in it by the likes of the New Horizons spacecraft, the Parker Solar Probe and others) referred to as the Heliophysics Mission.

The Heliophysics Mission fleet provides invaluable insights into our Sun, from understanding the corona or the outermost part of the sun’s atmosphere, to examining the sun’s impacts throughout the solar system, including here on Earth, in our atmosphere, and on into interstellar space. Over the last 45 years, the Voyager missions have been integral in providing this knowledge and have helped change our understanding of the sun and its influence in ways no other spacecraft can.

– Nicola Fox, director of the NASA’s Heliophysics Division

Voyager 2 left the heliosphere on November 5, 2018. Credit NASA/JPL
Today, as both Voyagers explore interstellar space, they are providing humanity with observations of uncharted territory. This is the first time we’ve been able to directly study how a star, our sun, interacts with the particles and magnetic fields outside our heliosphere, helping scientists understand the local neighbourhood between the stars, upending some of the theories about this region, and providing key information for future missions.

– Linda Spilker, Voyager’s deputy project scientist at JPL

Continue reading “Space Sunday: Voyager at 45”