All tests in a vacuum were miserable failures. Mythbusters spent 2 minutes on the subject and lied their faces off. In short they ended up editing their video because they used a separate camera to show the vacuum gauge in a vacuum. The problem is that when they were building the chamber they showed a different gauge. That is why they edited that part out. Plus they had it close to the back wall. The other 2 I found were done by the same guy and an 8 second rocket engine burned up in 1 second. In the second video he did a bigger rocket engine. At first he couldn't get it to ignite, then when he did it burned in 1.9 seconds. He wouldn't state the engine size or time of burn. You can not build a big enough chamber to do a test. To get even close to the vacuum of space is near impossible. If we can only find a way to mimic the vacuum of space in regards to propulsion .