The Space Power Facility at NASA Glenn Research Center's Plum Brook Station in Sandusky, Ohio, houses the world's largest vacuum chamber. It measures 100 feet in diameter and is a towering 122 feet tall. The facility is currently undergoing construction to support Orion crew exploration vehicle testing in 2010. Making its first flights early in the next decade, Orion is part of the Constellation Program to send human explorers back to the moon, and then onward to Mars and other destinations in the solar system.
Wow.. that really, really sucks.
This has a brief appearance in the Roving Mars omnitheater film making the science museum circuit, when they're testing Spirit or Opportunity (wasn't sure which). I didn't know what it was called, though, so thanks!
Let's see... the force of air pressure at sea level (we'll assume Sandusky is close enough) is 14.7 lbs per sq inch. There are 144 sq inches in a sq ft. That's ~2117 lbs per sq ft. Judging by the far door, which looks like it goes about halfway up the height of the chamber, and is close to as wide as it is tall, that'd be a 60x60 door. 60 x 60 x 2117 = 7,621,200. Or approximately 3.3 million tons of inward force on the door when there's a good vacuum inside.
"The door, weighing in at 675,000 pounds, must be built in place due to its size."
Haha. I wonder how much the vacuum equipment to suck the air out of this thing costs...
The photograph is not just awesome in composition, perspective, etc., but the inside walls of the chamber are exactly how inside walls of giant chambers are supposed to look.
I still think it should have more useless blinky lights and controls for doomsday devices, myself.
My first thought was "so that's what iRobot's contract with the government is for!" But unfortunately it looks like their military robots do not include weapons-grade vacuum cleaners.
Maybe everyone knows this, but maybe they don't. I thought it was pretty darn novel when I learned it, so I figure I should share.
My grandfather is an optical physicist who works with thin-film coatings for optics. At the level he is at, it's not like you can just spray the coatings on with an air compressor. Instead, you need to have the optics in a vacuum chamber wherein you can be sure that nothing, not even air, is going to come between the coating and the optics.
It turns out that vacuum pumps will only get you so far -- they can't get every last bit of air out of a chamber. No matter how small the chamber is, nor how powerful the pump is, basic physics says that you're pretty much always going to have some air left. To go beyond that, you need to have a few tricks up your sleeve.
The one trick he was willing to show me was an oil fountain. By spraying a fountain of heavy oil into the chamber, most of the remaining air molecules get trapped in the oil and fall down into the reservoir at the bottom. Do this for a few minutes and as long as your fountain has good coverage you can get almost every last molecule of air out of the chamber.
So when I see a chamber that big, I have to wonder if they are going to use a similar system. And if so, that's a heckuva lot of oil.
What you're describing is a diffusion pump, which is a type of vacuum pump. The oil is not sprayed directly into the chamber, but inside the pump body. In fact when diffusion pumps fail they can spray oil into the chamber and this makes a huge mess. They are used to get a higher quality vacuum than what is possible with a mechanical pump. A mechanical pump can get a chamber down to pressures of about a millitorr (10^-6 atm), but diffusion pumps can get down to high vacuum pressures of 10^-8 torr (10^-11 atm). Turbopumps and cryopumps can also get down to these pressures and lower, but operate via different principles.
I was wondering myself what NASA uses to pump out this chamber. My guess is that they're only interested in the mechanical stresses on the spacecraft, so high vacuum is unnecessary. They probably have an array of Really Big mechanical pumps to get a rough vacuum.
Never mind the last bit. After some googling I found their capabilities page: http://facilities.grc.nasa.gov/spf/capabilities.html
They can in fact get the chamber down to 10^-6 torr using an armada of diffusion pumps and cryopumps. Wow.
Have you noticed how many
great terriblegreat band names there are on this page? Cryoshroud. Space Power Facility. Test Chamber. Cold Wall. Contamination Control. Negative Pressure. Isolation Gate. Solar Simulator.
But can it lift a bowling ball? and where are you gonna find bags to fit it?
Wow. They must have some biiig dust bunnies.
I'm glad I don't have to do bakeout on that fucker.
Is flipping the the same sized power switch and waiting a bit longer really that much additional hassle?
How do you suppose they heat the walls of the chamber enough to allow it to outgas? I dont see anything about a GN2 temp conditioner to pump hot gas through that shroud. I suppose they might have AC or DC heaters on the chamber wall. To be honest I am curious now.
Well, the information I've seen on the chamber isn't completely detailed in the first place. For one, they don't mention their first stage pumps: you can't pump down from atmosphere with only diffusion and cryo pumps.
With that omission there's no telling what the advertised base pressure actually refers to. It could be the pressure in the lines leading to the pumps, for all we know. They could just let outgassing happen normally and pump as fast as they can, getting to a chamber pressure a bit higher than their stated base pressure.
Found some stuff.
"These facilities utilize rotary piston vacuum pumps to achieve simulated space vacuum environments....Vacuum Facility No. 5 has four dedicated vacuum pumps with three actively operating during facility testing. The fourth pump was held back in an annual rotational rebuild cycle, which resulted in each pump being used for three years before being rotated for rebuild. The relative ages of the three remaining in-service pumps were then staggered to one, two and three years since being rebuilt."
As far as a bakeout goes I am guessing they might only bake out that cold wall. Maybe they figure the fact that its massive surface area is cold through the whole course of test operation that contamination is more likely to migrate there then the walls of the chamber. Since it says that they can get the cold wall temp up to 70C they could just sweep the chamber and count of laminar flow to the rough pumps to clean the chamber.
The company I work for was looking into leasing this facility. The plan was to build a cryo shroud inside the chamber to get a more realistic space simulation.