Bob CollinsPresident Barack Obama outlined his plan for the U.S. space program today, arguing he doesn’t want the country “to do the same old thing,” and indicating that he wants the country to put a human on Mars.
His comments echoed those of a guest on MPR’s Midmorning on Monday, who said the manned space program now consists primarily of “going around in circles.”
There’s more to a space program, though, than just pointing a spacecraft at an object and hitting “go,” as Monday’s program pointed out. There’s also more to space than just visiting another planet. One guest on the program noted that the idea of “mining” an asteroid for many of the precious minerals we’re trying to find on earth is not — pardon the expression — pie in the sky.
Indeed, Mr. Obama mentioned that landing on an asteroid could be accomplished by 2025; landing on Mars could happen by 2035.
Then, again, in the ’60s, babyboomers were told they could go into space someday and, of course, our time has run out on that dream.
Even in 2000, a Time Magazine article claimed mankind would be on Mars by 2007.
So what’s the problem? Simple. We don’t know how, as Nancy Atkinson at Universe Today so cleverly explained a few years ago:
“The great thing about Earth,” said Manning “is the atmosphere.” Returning to Earth and entering the atmosphere at speeds between 7-10 kilometers per second, the space shuttle, Apollo and Soyuz capsules and the proposed Crew Exploration Vehicle (CEV) will all decelerate to less than Mach 1 at about twenty kilometers above the ground just by skimming through Earth’s luxuriously thick atmosphere and using a heat shield. To reach slower speeds needed for landing, either a parachute is deployed, or in the case of the space shuttle, drag and lift allow the remainder of the speed to bleed away.
But Mars’ atmosphere is only one per cent as dense as Earth’s. For comparison, Mars atmosphere at its thickest is equivalent to Earth’s atmosphere at about 35 kilometers above the surface The air is so thin that a heavy vehicle like a CEV will basically plummet to the surface; there’s not enough air resistance to slow it down sufficiently. Parachutes can only be opened at speeds less than Mach 2, and a heavy spacecraft on Mars would never go that slow by using just a heat shield. “And there are no parachutes that you could use to slow this vehicle down,” said Manning. “That’s it. You can’t land a CEV on Mars unless you don’t mind it being a crater on the surface.”
Perhaps one of the reasons President Obama mentioned 2025 and 2035 is because it creates the notion that something we try in this lifetime, will have a payback in this lifetime (See NPR’s “Why have a space program at all?“). But increasingly, meaningful exploration in space is going to require the expenditure of money and effort in this lifetime, for a payback in someone else’s lifetime.
That’s not our strong suit.
