To the Kármán Line

Originally published at:

Doing what X-Plane makes fun and exciting, we take a ride to the edge of space in the X-Aerodynamics White Knight Two and SpaceShip Two. Sub-orbital flight is fun! As many of you already know, I have a long running fascination with the early space program, to include the post WWII continuing development of jet…


@AeroMechanical (and I wish @EinsteinEP) - I would love some feedback on everything I got wrong in this article…! :rocket: :rofl:

I specifically had a question - why does SpaceShipTwo not have to contend with the heating problems that the X-15 had to deal with? I mean, it is coming down (more vertically) at M3.0 or so…I would have thought the bottom of the vehicle would get as hot as the X-15?

Well, referencing its predecessor:

The ship converts (via pneumatic-actuated feather) to a stable, high-drag shape for atmospheric entry. This “care-free” configuration allows a “hands-off” re-entry and greatly reduces aero/thermal loads.

So, it’s the “shuttlecock” mode that enables that, as you mention in the article! Much less severe than the conditions the X-15 saw. I’ll elaborate more soon…

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Yeah, I figured that had something to do with it. The “shuttlecock” mode perhaps lets it penetrate into the atmosphere at a steeper angle with less speed as opposed to the X-15 that needed a lot of forward momentum and sliced more diagonally through the atmosphere for a longer period, heating it up for a longer duration. I would have thought that the steeper descent of the Scaled planes would have had higher G-loading but maybe not. Whatever the case, SS1 and SS2 look pretty flimsy…but they must be constructed to pretty high tolerances.


Here is a great video of SpaceShipOne making a similar type flight profile…it is interesting to see the data readout on the left side showing the altitude, G, and Mach number… Looks like a maximum G of around 3.1 or so at around 100,000’ and Mach 1.5 with a maximum Mach of 2.48 on the boost and M 1.93 on the feathered recovery.

Isn’t heat a function of pressure (IAS) as much as compressibility? Early 60’s near space flight was done in planes that held high Mach values to relatively low altitudes. Thus the heat. SS1 quickly transitions to GA speeds as the atmosphere thickens.

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CNN article where Richard Branson implies that space is within the reach of SpaceShipTwo…perhaps before Christmas! Caution - the interviewer is really…uh grating…for some reason. I wish I could have interviewed him!

“Branson is known to set deadlines that aren’t met. Virgin Galactic has been developing SpaceShipTwo since 2004, and Branson initially said commercial rides would begin in 2007. Eleven years later, the firm is still working on getting its 600 customers into space.”

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Looks like they made it to 50 miles…!

271,268’ and Mach 2.9…!

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Until this thread I had never heard of the Karman line. Now that I have, I say Virgin came up 14 miles short.

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They get any higher and they may see Aurora flying around the dessert.