Astrium was an assignee, and proceeded to register it in patent offices of US, Russia, Australia, Japan, and European Union the next year. It is unclear how many people worked on the idea and how seriously it was really taken, but the patent was quite definitely not a bogus one. 

It cited problems with the safety of the ex-Soviet aircraft, describing a necessity to mount the passenger compartment on latches or explosive bolts. The capsule would have a life support system, canopy with 180° overhead view, and could sit between 4 and 12 people depending on the carrier – plus one flight attendant. Since such a contraption would result in immense drag, an additional rocket engine – either integrated into the capsule or a detachable one – would have to be fitted. Migbus patent drawing AeroTime News

A scheme, detailing the attachment and layout of the capsule, as well as additional modification of the aircraft. From the patent issued by United States Patent and Trademark Office in 2002. (Image: Astrium GmbH / Google Patents)

The patent used MiG-31 Foxhound as an example of a possible carrier. It was more advanced, more powerful and more robust successor to the Foxbat, but even its massive engines did not have enough power to carry the capsule at supersonic speeds, and it was just as difficult to control in the thin air of the stratosphere as any other aircraft. Therefore, the patent proposed attaching underbelly booster rocket, and adding multi-axis thrusters in the nose to improve controllability.

At some point Astrium signed a memorandum of understanding with MiG scientific-industrial complex, the former Mikoyan and Gurevich constructor bureau. EADS report, released in 2004, actually says that the capsule concept itself was designed by MiG and that there is a lack of technical information about the project because the flight characteristics of the fighter jet are still classified. But, it assures, the project moves forward: an application letter is filled to German airworthiness authorities, a model has been tested in a wind tunnel by MiG, and a German professor Peter Sacher has completed his preliminary evaluation of the concept. 

“No major showstopper was identified,” the report states, but the “project is now in stand-by as for the moment it is lacking of financial support.”

migbus render AeroTime News

Promotional render for the Migbus. (Image: EADS Space Transportation)

Several years later, the German patent was withdrawn and the U.S. patent expired due to “fee-related” causes. 

There are at least a couple of 3D renders floating around the Internet, showing Migbus in varying levels of detail. The simplistic one is from EADS space tourism report, and represents just a rough idea, without proper scale. A bit better one can be found in German newspapers of the period, depicting a bottle-shaped passenger capsule with a sharp nose, rocket boosters and a pair of additional stubby wings. No pictures of the wind testing model can be found anywhere, and the Russian side of the internet, which often displays peculiar fascination with similar crazy ideas, contains no information on "Mig" part of Migbus. This very well might indicate that the advanced state of the project within MiG, described by the report, could have been a bit exaggerated.

EADS completed its transformation into Airbus a decade later, with Astrium – now EADS Space Transportation  proposing and jettisoning at least several other space tourism ideas in the meantime. Then, the geopolitical situation got cold again and Russia modernized its remaining MiG-31s, returning them to active duty, and destroying any possibility of commercial use. 

While the process behind the fast demise of Migbus is not entirely clear, the craziness of the idea, and the difficulty of its execution, are rather apparent. Still, experiencing or just seeing it in flight, would have been something quite impressive