The Edge of Space

The Edge of Space and the Karman line

On 11 July 2021, Sir Richard Branson, founder of Virgin Galactic, took a suborbital flight to the inner edge of outer space, reaching an altitude of 86 km (54 miles) above the surface of the Earth. Although it marked a milestone for space tourism, where that milestone marker should be placed is an ongoing matter of debate.

Ahead of Branson’s flight on 11 July, social media (including a tweet by Blue Origin and Amazon founder, Jeff Bezos) was vacuum-packed with comments that Branson’s SpaceShipTwo spaceplane had not gone to space, but 14 km shy of it.

Bezos made his own commercial suborbital flight to the edge of space on 20 July 2021 as one of the crew of the RSS First Step capsule atop his New Shepard rocket. The capsule reached an altitude of more than 100 km (62 miles) before parachuting back to Earth.

For the edge of space currently has two recognised definitions, 20 km apart…

Virgin Galactic - VSS Unity 11 July 2021

According to one definition (the one recognised by NASA, the Federal Aviation Administration (FAA), US Air Force and US Space Force), outer space starts at an altitude of 80 km (50 miles).

According to another definition (the one recognised by the Fédération Aéronautique Internationale (FAI) or World Air Sports Federation, the governing body that certifies air and spaceflight records), outer space starts at an altitude of 100 km (62 miles). That boundary is currently known as the Kármán line.

It’s like Amazon drivers: some deliver your package to your apartment door on the top floor, while others may choose to leave it on the stairs partway up. In both cases, it’s officially been delivered.

However, the FAI may be about to redefine down the altitude of the boundary they recognise, from 100 km to 80 km, in line with NASA.

And if that’s not enough, on 20 July 2021 the FAA tightened up its eligibility requirements for being awarded Commercial Space Astronaut Wings.

It’s all change on the commercial space bus. But more on all that later.

The first

Along with the competition between Branson and Bezos as to whose commercial flight went into space, is the matter of time and who got there first.

The spat brings to mind the notorious race to space 60 years ago, when during the first few months of 1961, Yuri Gagarin beat Alan Shepard to become the first human to go into space. Shepard, the astronaut after whom Bezos named his New Shepard rocket, was pipped to the post by a matter of weeks.

Shepard is said to have banged his fist so hard on the desk when he heard the news of Gagarin’s flight that some thought he may have broken his hand and jeopardised his own flight. One can only speculate on the reaction of Bezos when news broke on 2 July that Branson was planning to launch his own flight just nine days before Bezos had already announced he was flying on 20 July.

We do know that Blue Origin vented on Twitter posting gems such as “…none of our astronauts have an asterisk next to their name. For 96% of the world’s population, space begins 100 km up at the internationally recognized Kármán line,” before wishing Virgin Galactic a great flight the next day.

Virgin Galactic - VSS Unity - 11 July 2021 - The Edge of Space and the Karman line

Elon Musk, founder of SpaceX, did not publicly comment on the edge of space debate on this occasion, but on 11 July he was reportedly at Spaceport America to cheer Branson and the crew of VSS Unity on their way to the edge of space. And he sent a congrats tweet to Blue Origin on RSS First Step‘s first human flight on 20 July.

SpaceX is already flying commercial astronauts beyond the edge of space in its Crew Dragon spacecraft. In May 2020, it became the first private space company to send humans into orbit, including to the International Space Station orbiting 460 km (260 miles) above the Earth. (A reminder here: Branson and Bezos don’t go into orbit, but sub-orbit). Then in September 2021, SpaceX will take its first all-civilian crew of space tourists into orbit 540 km (335 miles) above the Earth, and in 2023 it plans to orbit the Moon.

After that, well…is anyone watching The Expanse? On Amazon.

Debating where space starts has been ongoing for over six decades (the documented stuff, at least) and some say that trying to establish a significant demarcation for the start of space based solely on aerodynamics is too convoluted to determine. However, an official or legal definition agreed by all is becoming more desirable with the commercial space industry and space tourism taking off before our eyes.

But how high the sky is just one small difference between the Virgin Galactic and Blue Origin space tourism ventures.

Blue Origin New Shepard

The vehicles

Virgin Galactic’s vehicle, SpaceShipTwo, is a rocket-powered spaceplane that is carried to altitude by WhiteKnightTwo, a four jet-engined carrier plane. On 11 July 2021, the spaceplane was VSS Unity and the carrier was VMS Eve.

The carrier plane takes off and lands on a conventional runway, dropping the spaceplane off at around 15 km (50,000 ft). The spaceplane’s rocket engine then propels it upwards near-vertically to above 80 km. On the way up, passengers feel more than 3 g-forces (on Earth we feel 1 g) — which is about half of the force they will experience on the descent.

Reaching the top of the arc, passengers will see the blackness of space and experience approximately 4 minutes of microgravity. For the descent, the spaceplane folds up (feathers) its wings to reduce drag until it reaches about 50,000 ft when the wings fold down and the spaceplane glides to a conventional runway landing.

The whole flight lasts just over an hour. The spaceplane’s independent part of the flight, after release from the carrier, lasts about 15 minutes.

Virgin Galactic SpaceShipTwo VSS Unity and the edge of space and the Karman line
Virgin Galactic

The ride on Blue Origin’s New Shepard vehicle lasts just over 10 minutes, on a flight which is more like a traditional rocket launch. On 20 July 2021, RSS First Step flew.

The passenger capsule is launched atop a booster rocket, separating at around 80 km (a few km below the altitude at which the Virgin Galactic flight peaks). The capsule then continues upwards into its parabolic arc, peaking just after the 100 km Kármán line.

Passengers experience similar g-forces and length of time in microgravity as those on a Virgin Galactic flight. Near the end of the (perhaps uncomfortable) downward trajectory, a parachute opens to aid a gentle landing in the desert.

The capsule incorporates a means of propelling itself away from the rocket booster after separation, in the event the booster malfunctions. The booster falls back to Earth, maintaining its attitude for a vertical landing on a designated landing pad a few kilometres from the launch pad.

Watching the booster undertake its autonomous landing must be as thrilling a sight for those on the ground, as the sight of Earth and outer space for those in the capsule.

Blue Origin flight path to the edge of space and the Karman line

Space tourists

Putting aside where the edge of space is for a moment, Branson’s flight was a great day for space tourists — or for those with a stack of money. But there is a glimmer of hope for those who don’t have a spare $250,000 (or thereabouts) knocking around to spend on a suborbital ride to the edge of space (or thereabouts).

Shortly after his return from the hour-long trip, Branson launched a competition on Omaze for someone to win a pair of tickets on a Virgin Galactic suborbital flight in early 2022.

I thought I would enter the competition — but changed my mind after reading the terms that apply to non-US residents. If, like me, you are not a US resident, you too may want to read through the terms of the prize, thoroughly, before you press the competition’s enter button. Unless a lawyer happening to read this article can explain the onerous tax tone?

And who were lucky enough to fly to the edge of space with Branson and Bezos?

On 11 July, Branson’s three crew mates were all employees, one overseeing the test flight (looking rather nervous, I thought, for someone who had done this flight before) and two others evaluating cabin procedures and the researcher experience.

Virgin Galactic - VSS Unity - the edge of space

On 20 July, Jeff Bezos, who had earlier stated, “If it’s not safe for me, it’s not safe for anyone,” was accompanied by his younger brother, Mark, who has his own private equity firm and is a volunteer firefighter.

Also onboard was 82-year old veteran professional pilot Wally Funk. She went through astronaut training in the 1960s as part of a privately-funded female astronaut training program but the program was cancelled. NASA did not recruit any women astronauts until the late 1970s.

Also on the flight was 18-year old Oliver Daemen, the company’s first paying passenger. A newly qualified private pilot, his family reportedly paid $28 million for his 10 minute flight after the previous passenger pulled out due to some kind of diary clash (civilian space travel is already beginning to sound like any normal day in the office).

Blue Origin’s CEO reportedly told CNN the day before the launch that “there’s really nothing for a crew member to do” but that some of the passengers would undertake evaluations in the autonomous capsule.

Blue Origin made a point of using the hashtag #NSFirstHumanFlight for the New Shepard flight on 20 July. That alone made me wonder.

But back to the first key question…

How high is the sky?

The inner edge of outer space is the altitude at which aerodynamics (i.e. airspace) gives way to astronautics (i.e. outer space) — in a nutshell, where Earth’s atmosphere becomes too thin to support air flight so that aircraft wings become redundant.

That altitude is sometimes associated with the mesopause, the altitude which marks the boundary between the thermosphere (above the mesopause) and the mesosphere below. The mesosphere is the layer where most meteors burn up due to ablation by friction with particles in the atmosphere. Above the mesopause there are fewer particles to cause the friction.

The Edge of Space and the Karman line

The most well-known name associated with the altitude at which space begins is Theodore von Kármán, a Hungarian-American aerodynamicist. It was in the late 1950s that the term Kármán line was coined for the boundary to space. At that time, it was associated with an altitude of about 84 km (52 miles). Documentation also shows the Kármán line being referred to in the early 1960s by Andrew Haley, he who is now referred to as the first space lawyer.

Also in the 1950s, others referred to space beginning at an altitude of 100 km (62 miles), including members of the Fédération Aéronautique Internationale (FAI) and the Legal Subcommittee of the ad hoc Committee on the Peaceful Uses of Outer Space (COPUOS). For now, 100 km remains the altitude at which many international organisations consider space to begin.

But NASA doesn’t always use its own definition of 80 km, since there is a statement on the NASA Earth Observatory website that reads “Technically, there is no absolute dividing line between the Earth’s atmosphere and space, but for scientists studying the balance of incoming and outgoing energy on the Earth, it is conceptually useful to think of the altitude at about 100 kilometers above the Earth as the ‘the top of the atmosphere’.”

Consensus may, however, be just over the horizon. On 30 November 2018, the FAI issued a statement that they are considering lowering the altitude of the boundary to space because “recently published analyses present a compelling scientific case for reduction in this altitude from 100km to 80km.”

The FAI statement doesn’t quote any specific scientific research, but in a paper published in Acta Astronautica a month earlier, in October 2018, Jonathan MacDowell, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, put forward a compelling set of arguments for redefining the boundary for the edge of space to 80 km (50 miles) — so let’s assume the FAI is referring to that. You can read the paper here.

You can also sit back and enjoy a 27-page discussion of the history of determining the edge of space (Kármán line or otherwise) here. It really is enjoyable. Written by Thomas Gangale, a Doctor of Juridical Sciences in space, cyber and telecommunications law at the University of Nebraska-Lincoln, the paper serves as a myth-busting guide to the Kármán line for the perplexed.

The Edge of Space and the Karman line

Breaking records

Whatever your own aerodynamical and astronautical calculations scribbled on the back of an envelope, napkin or beer mat may be for the edge of space, the Virgin Galactic flight on 11 July 2021 broke two records:

Firstly, the record for the greatest number of people on a single suborbital flight (six people), and secondly, for contributing to the greatest number of people in space at one time (16 people when combined with those residing on the International Space Station at the time).

The Blue Origin flight on 20 July 2021 achieved firsts for Wally Funk and Oliver Daemen, who, respectively, became the oldest and youngest people to fly to the edge of space…and Jeff Bezos, the richest.

And the third man? Well, SpaceX holds the record for the largest number of firsts.

The question is, are the Virgin Galactic and Blue Origin crew members officially commercial astronauts?

US Federal Aviation Administration Commercial Astronaut Wings (version 2). First used in 2018 (Credit: FAA)

Flying without wings?

On 20 July 2021, the FAA published an order revising its Commercial Space Astronaut Wings Program. Effective date: 20 July 2021 — the day of the Blue Origin flight.

In the order, the FAA refines the eligibility requirements for a crew member to be awarded Commercial Space Astronaut Wings. Paragraph 5 of the the order (8800.2) reads:

And the crew qualifications and training requirements under Title 14, part 460, subpart A, section 460.5:

As well as satisfying the eligibility requirements, a crew member needs to be nominated by the FAA (or other official nominating body). Honorary awards of wings are also available and the eligibility requirements may be waived for such individuals “whose contribution to commercial human space flight merits special recognition”. The FAA says it may refine the eligibility requirements for Commercial Space Astronaut Wings at any time.

You can read the whole of Title 14 and part 460 here.

Promoting records

Always the music man, it was inevitable that Branson would incorporate some form of record promotion with his inaugural flight on 11 July. Retired astronaut and former ISS Commander Chris Hadfield (now a member of the Virgin Galactic Space Advisory Board) took the lead on this, spending a not insignificant amount of time interviewing singer-songwriter Khalid about his single New Normal, a song which was played to the Virgin Galactic astronauts during their flight and performed live to the crowd on the runway.

Asked what he thought about the day, Khalid said, “It’s so surreal. I think that’s kind of how we all feel about the times right now, super surreal. But it’s true, it’s our new normal so we’re gonna have to get used to it.”

To me, this was as surreal as the time when the PI of the New Horizons mission had Brian May compose and perform a song for the fly-by of the distant Kuiper Belt object Ultima Thule (486958 Arrokoth) in 2019.

But back to Spaceport America and Hadfield informed us that Khalid holds the record for being the youngest person ever to hit 20 billion streams on Spotify, adding, “What we really need is [sic] ships like this one behind us that can let people get up there — people with your kind of talent to then share it in way that other people can really understand.”

I’m not too familiar with Khalid’s work, nor that of DJ Khaled with whom some, it seems, get Khalid confused. Although I got confused with another mononymous Khaled.

When I first heard the name of who was going to be performing a new single at Spaceport America, my aging ears pricked up thinking it was Khaled, the Algerian Raï singer who was huge in the 1990s, only to be let down when I realised it wasn’t him. (If you think you haven’t heard that Khaled’s work, but have seen the 1997 sci-fi movie The Fifth Element, you heard it in the flying car chase, for instance.)

The Fifth Element (1997) featuring flying cars and Cheb Khaled

But back to Spaceport America, and asked what he would take if he went to space, Khalid said would take a crystal. Although he didn’t elaborate, my guess is not a stack of the piezoelectric kind that might power a propellant-less propulsion drive in the future.

Onwards and outwards

Introducing the astronauts after their flight on 11 July, Michael Colglazier, CEO of Virgin Galactic, reminded us that VSS Unity was named by the late Professor Stephen Hawking, who in 2016 had said, “The first private astronauts will be pioneers. We are entering a new space age and I hope this will help to create a new unity.” At the end of his speech on 11 July, Branson reinforced the message, stating, “Welcome to the dawn of a new space age.”

As I listened to talk of space tourism and private space stations becoming the new normal, the opening titles of The Expanse flashed before my eyes — with humans moving off the planet, terraforming Mars, mining the asteroid belt, farming soya beans on Ganymede…splinter groups, stealth technology, interplanetary disputes and weaponised asteroids.

It was all a little dramatic perhaps — but I love astrotainment.

The Blue Origin post-flight press conference on 20 July had more of a philanthropic focus. Although Bezos did thank the millions of Amazon customers, saying: “Seriously, you paid for this.”

Virgin Galactic - 11 July 2021 - crew members

Although I am no fan of heights and, if I were to be honest, do not enjoy flying (preferring an aisle seat, up front and near the door), I would go on any one these flights in a very rapid heartbeat. If I had the cash. But I’ll go as a test case — really, I don’t mind.

I signed up for potential employment opportunities with Virgin Galactic at the very beginning of its venture…but I heard nothing back. I’m still waiting. And like the fictional character Eleanor Arroway, I’m OK to go.

But I’ll end this post now before I veer off course any further than I already have.

Note: This is an update of an article originally posted on 11 July 2020.

Papers cited

Fédération Aéronautique Internationale (World Air Sports Federation). “Statement about the Kármán line.” FAI website. Accessed 11 July 2021. https://www.fai.org/news/statement-about-karman-line

Gangale, Thomas. “The non Kármán line: An urban legend of the space age.” J. Space L. 41 (2017): 151. https://airandspace.confit.dev/wp-content/uploads/2020/07/JSL-41.2.pdf

McDowell, Jonathan C. “The edge of space: Revisiting the Kármán line.” Acta Astronautica 151 (2018): 668-677. https://doi.org/10.1016/j.actaastro.2018.07.003

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