A union representing about 570 United Space Alliance space shuttle program workers at the Kennedy Space Center voted to strike Saturday morning after unsuccessful contract negotiations. The bargaining team for the International Association of Machinist and Aerospace Workers rejected the company's contract offer calling it "substandard" compared with other aerospace companies, said Lynn Beattie, a member of the bargaining team and former Local 2061 president.Health care and retirement benefits were among the major contract grievances."It was a sub-par contract," said Johnny Walker, union business representative. "They are not keeping up to par wages-wise."Both sides will have a chance to solve the conflict during a five-day "cooling off period" but the union could strike as early as midnight June 9."If they want to avoid a strike, the ball is in their court," Walker said.Tracy Yates, spokeswoman for United Space Alliance, said the company was "surprised and disappointed.""The final offer was fair, competitive and responsive in every area," she said.In a statement released Saturday, the company said it would use other employees to prepare for upcoming launches if a strike occurs.No rule prevents Local 2061 workers from walking off the job shortly before a shuttle launch, Yates said.