Tom Clancy meets NASA in this gripping alternate history scientific thriller. "A brilliant tale of industrial espionage and sabotage. An insider's look at the secretive world of space exploration." --Nelson DeMille "Move over Tom Clancy, there's a new kid on the block." --Library Journal on Ultimatum Years before NASA planned to travel to Mars, and before the International Space Station ever reached orbit, the future of America's space program hung in the balance.After the tragedy of the Space Shuttle CHALLENGER, the technicians of NASA hoped to create a failsafe shuttle, incapable of malfunctioning. With the brand-new Space Shuttle LIGHTNING, all systems were go . . .Then lightning struck twice.SIEGE OF LIGHTNINGAmerica's greatest technological achievement has been sabotaged. First an engine malfunctions. Then, another. Now LIGHTNING is desperately trying to land, racing against time--and a powerful and unseen enemy will do anything to make the first flight of LIGHTNING its last . . ."Chilling . . . a riveting climax."Joe Weber, bestselling author of DEFCON One"Heart stopping . . . one of the best thrillers of the year."--Charles Ryan, author of The Capricorn Quadrant"Gripping, spine-tingling and explosively brilliant."--Guy Durham, author of Stealth and Extreme Prejudice