The space shuttle Columbia appeared to have passed one of its last critical tests yesterday, suggesting that astronauts John Young and Robert Cripppen will fly it into orbit on Columbia's maiden flight from Earth as early as April 9.

The space agency will not fix a date for Columbia's flight until Monday but National Aeronautics and Space Administration officials in Washington and Cape Caraveral were talking yesterday as if Columbia would roar away from the Kennedy Space Center the morning of April 9 or 10, depending on how conservative test engineers decide to be in the next 10 days and how a second test of the hydrogen fuel tank goes today.

In a critical test Wednesday, more than 1.5 million pounds of supercold liquid oxygen and hydrogen were pumped into Columbia's huge external fuel tank to see how insulation panels outside held up. As far as anyone could tell yesterday, the insulation held up very well, appearing to suffer none of the cracks and "debonding" it underwent in a Jan. 22 test.

"We won't really know if the external tank passed its tests until we do a closeup tank inspection over the weekend," one shuttle test engineer said yesterday. "What we've seen so far with television cameras and telescopic lenses is very encouraging."

Today's test also involves the pumping of 1.55 million pounds of fuel into the external tank but at a less stressful pressure than Wednesday's test. That was a proof test of the tank's insulation to make sure ice will not form on the tank's exterior and damage the shuttle's heat-resistant tiles by falling off on them during launch. Today's test is to make sure the procedures for filling the tank before launch are precise and complete.

Wednesday's test seemed to have gone off without a hitch, with no ice forming on the outside of the tank and no vapors seeping out of it, which would have been the signs that the insulationpanels were not bonded tightly enough. The temperature of the liquid oxygen in the tank is 297 degrees below zero Fahrenheit and of the liquid hydrogen 423 degrees below zero.

On the minds of the shuttle test engineers is the death last week of a technician who prematurely entered an aft shuttle compartment after it had been filled with nitrogen to minimize fire hazard. Test engineers are poring over past procedures to see if any must be changed to prevent a repeat.