WASHINGTON – As Virgin Galactic is approaching the first submarine flights in space, a potential change in terminology could make it easier for the company to reach that milestone.
In an interview with CNN published on November 30, Virgin Galactic founder Richard Branson said the company was within weeks of flying the SpaceShipTwo sub-planetary space plan in space. This vehicle, called VSS Unity, is carrying out a series of tested flights, recently on July 26th.
"The space is difficult," Branson said in response to a question citing unnamed critics who did not believe the company would be able to reach space with SpaceShipTwo. "Obviously, we would like to prove our critics and I am reasonably confident that before Christmas we will do it."
Branson suggested in a October interview with CNBC that spaceShipTwo's first space flight would come in "weeks, not months." The company's officials at that time declined to comment on that schedule, adhering to the long-standing policy of admitting Branson's schedule and deadlines, although they said they were planning to conduct at least another test drive flight before the end of the year.
George Waitsides, the chief executive of Virgin Galactic, did not give a specific timetable in November 27th at SpaceCom Expo in Houston, but suggested that more and more altitudes would be expected soon. "The next few flights will be even more exciting" than the July flight, which peaked at 52 kilometers above sea level, he said. "We'll see some of them soon."
In July, the flight involved 42 seconds of burning a SpaceShipTwo hybrid rocket engine, designed to fire about 60 seconds on a typical flight. "We are at the point where we want to add a lot of apogee if we continue to ignite the missile engine," Whitesides said during a dinner at the 2 November Space Session at Los Angeles.
One issue is that it will need to reach the height of SpaceShipTwo, to be considered to reach space. While there is no formal boundary of space in contracts or law, the industry often used an altitude of 100 kilometers, known as the Pocket Line by late aviation engineer Theodore von Karman. That definition gained momentum during the Ansari X competition for commercial substandard vehicles, conquered by SpaceShipOne in 2004 when flying over that altitude twice in two weeks, as well as during a test flight three months earlier.
There has been speculation in the industry, however, that SpaceShipTwo will not be able to reach that altitude in its current configuration with full loads of participants in the field or experiments on the ship. Whitesides, asked for altitude in his conversation in Los Angeles, is instead calling for a lower altitude used by the US government.
"For Virgin Galactic, the main milestone we are experiencing is the altitude at which NASA and the aviation forces receive their astronautic wings, which is 50 miles," he said. "For us and our customers, I think we will be focused on 50 miles, at least initially."
International bodies are now revising the definition of the line of Karman. In a statement on November 30th, the Federation Aeronautics International (FAI), the world aerospace federation that maintains aviation and spaceflight records, said it would co-operate with the International Astronautical Federation (IAF) to revise that altitude to be considered a boundary of the space for record purposes.
"The recently published analyzes are a serious scientific case for reducing this altitude from 100 km to 80 km," the FAI said. Eighty kilometers is about 50 miles. FAI said it proposed to the IAF that "an international workshop is being held during 2019 to fully explore this issue with the entry and participation of astrodynamics and the astronaut community."
The FAI statement did not mention the specific analyzes that made it to reconsider the height of the Parma line. However, such a document was published recently in the journal Acta Astronautica by Jonathan McDowell, a historian of astronomers and spacecraft at the Harvard-Smithsonian Center for Astrophysics, who recommended a reduction of the Karman line at 80 kilometers.
This paper, in addition to examining the historical record, contains a broad mathematical analysis, forces for modeling the spacecraft traveling through the upper atmosphere. It concludes that for most satellites, gravity exceeded aerodynamic forces at an altitude of 70 to 90 kilometers. "Based on these physical, technological and historical arguments, I therefore suggest that the 80 km value is a more appropriate choice to be used as a canonical lower" edge of space "in conditions where such a line of separation between the atmosphere and space is desired," the newspaper .
Belgian media mentioned this paper in their comments last month. "If you look back in the history of the universe, it is not at all clear that Kárman really thought that 100 [kilometers] was really the right place, "he said." It's a kind of nice round number. "
That separation line was not a problem for the other company that operated a commercial system of human suborbital spacecraft. The new Blue Sheet Shepard has exceeded 100 kilometers on several test flights, including the latest on July 18, where the crew capsule reached a peak of 119 km, thanks to the use of its interrupted engine shortly after separation from the propulsion engine of the vehicle.