WASHINGTON – When Virgin Galactic approaches its first suborbital flight in space, a potential change of terminology can make it…
WASHINGTON – When Virgin Galactic approaches its first suborbital flight in space, a potential change of terminology can make it easier for the company to achieve that milestone.
In an interview with CNN published on November 30, Virgin Galactic founder Richard Branson said the company was within a few weeks of flying its SpaceShipTwo suborbital spacecraft in space. The vehicle called VSS Unity has performed a series of driven test flights, by July 26th.
“The room is hard,” Branson said in response to a question citing anonymous critics who did not believe the company could reach SpaceShipTwo. “Of course, we would like to prove our critics wrong and I’m pretty convinced that we will do it before Christmas.”
Branson had suggested in an October interview with CNBC that the first flight in SpaceShipTwo would come in weeks, not months. The company’s officials at that time declined to comment on that schedule and were in agreement with a long-term policy to allow Branson to set schedules and deadlines, even though they considered they planned to carry out at least one more driven test flight before the end of the year.
George Whitesides, chief of Virgin Galactic, did not give a specific schedule in a November 27th at the SpaceCom Expo in Houston, but suggested that more and higher altitude tested flights are coming soon. “The next flight will be even more exciting” than the Christmas fly, which reached a peak of 52 kilometers, he said. “We’ll see some of them soon.”
The July flight meant a 42 second burn of the SpaceShipTwo hybrid rocket engine, which is intended to shoot for about 60 seconds on a regular flight. “We are in place where we will add a lot of apogee if we continue to burn the rocket engine,” said Whitesides during a dinner call at the space launch ceremony on November 2 in Los Angeles.
One question is what height SpaceShipTwo needs to reach in order to consider reaching the space. While there is no formal limit for space in treaties or laws, the industry has often used the height of 1
00 kilometers, known as Karman Line after the late space engineer Theodore von Kármán. That definition became prominent during the Ansari X price competition for commercial suborbital vehicles, which was held by SpaceShipOne 2004 when it flew over twice twice within two weeks, as well as during a test flight three months earlier.
It has been industry speculation, however, SpaceShipTwo will not be able to achieve the height of its current configuration with a full payload of space fan partners or onboard experiments. Whitesides, asked about heights in his Los Angeles speech, instead referred to a lower altitude used by the US government.
“For Virgin Galactic, the great milestone we perceive is that NASA and Air Force people get their astronauts, which is 50 miles,” he said. “For us and our customers, I think we will focus on 50 miles, at least in the beginning.”
International bodies are now found in the Karman line definition. In a statement from November 30, Fédération Aéronautique Internationale (FAI), the world’s aviation federation, which maintained aeronautics and spaceflight records, announced that it would work with the International Astronaut Federation (IAF) to see what height should be considered as the limit of space for his record keeping purposes.
“Recently published analyzes present a convincing scientific case for reduction at this height from 100km to 80km,” said FAI’s statement. Eighty kilometers are about 50 miles. FAI said it was proposed to IAF that “an international workshop will be held in 2019 to fully explore this issue with input and participation from astrodynamics and astronautic society.”
The FAI statement did not mention the specific analyzes that led to reassessing Karman line height. However, such a paper was recently published in the journal Acta Astronautica by Jonathan McDowell, an astronomer and spacecraft historian at the Harvard-Smithsonian Center for Astrophysics, which recommended reducing the Karman line to 80 kilometers.
The paper besides investigating the historical record contained extensive mathematical analysis, modeling forces on a spacecraft traveling through the upper atmosphere. The conclusion was that for most satellites the gravity exceeded the aerodynamic forces at altitudes of 70 to 90 kilometers. “Based on these physical, technical and historical arguments, I therefore propose that a value of 80 km is a more appropriate choice to use as the canonical lower edge of space in circumstances where such a separation line between atmosphere and space is desired,” concluded the paper.
Whitesides referred to that paper in its comments last month. “If you look back in space history, it’s not clear at all that Kármán really believed that 100 [kilometers] was really the right place,” he said. “It’s kind of a nice round number.”
The division line has not been a problem for the other company operating a commercial human suborbital spacecraft system. Blue Origin’s New Shepard has exceeded 100 kilometers on several of its test flights, including the latest 18th of July, where the vehicle crew capsule reached a peak of approximately 119 kilometers due to the use of the interruption engine shortly after being separated from the vehicle propulsion module.