Fans will no doubt complain about a scientific inaccuracy tonight. The production crew wouldn’t let me bring real rocket fuel for the episode and instead used water. Apparently Warner Brothers has some rule against bringing hydrazine and nitrogen-5 onto their sets.
Hydrazine has a long history in the rocket world as a propellant. Its first use was for the German rocket-propelled military aircraft, the Messerschmitt Me 163 Komet. To date, the only such aircraft ever in regular operation.
When mixing the hydrazine with solvents, the Germans called the fuel “B-Stoff”. Today hydrazine is used for more peaceful purposes, such as adjusting the orbits of satellites and as auxiliary power for the International Space Station.
The hydrazine reaction was on tonight’s boards so it was a kind of spoiler for those paying attention.

The boards in an early scene show how hydrazine works as a rocket fuel... and foreshadows what happens next.
The concept the writers explained to me was that Leonard’s mistake was that something didn’t scale. They wanted that what would work for a real rocket, would not scale to the small amount of fuel he brought. The hydrazine reactions happen faster by exposure to the element iridium. The word chemists would use, is to say the reaction is “catalyzed” by iridium. A catalyst accelerates a reaction but is not used up. This is what the platinum does in a car’s catalytic converter and was the reason for the ‘iridium flask’.
By what is now the season’s third application of the square-cube law, the full amount of hydrazine would be exposed to a relatively small surface area of iridium. In Leonard’s small container, a far greater fraction of hydrazine is exposed to iridium, and as Sheldon realizes, becomes highly explosive as shown on the boards above.
We added some “Nitrogen-5”, or pentanitrogen, to sweeten the mixture. That was a fuel that was being developed in 2003, and would likely have some secret aspects Leonard should not discuss.
Not everything on the boards relates to rocket fuel. Recall it is 2003. Drs. Abrikosov, Ginzburg and Leggett had just received the Nobel Prize in physics
for pioneering contributions to the theory of superconductors and superfluids.
Their theoretical work is laid out on the boards as well, as something Sheldon would have been thinking about.
The whiteboards star the show once again. I don’t know why the director keeps letting the actors walk around and upstage them.
May 17, 2010 at 10:36 pm
I just watched the show but I can’t remember exactly, didn’t that white board have chemical equations on it at the beginning of the roommate interview? I’m pretty sure I was sitting there wondering why Sheldon cared about chemical reactions.
Thanks for the explanation. I think I can actually buy the idea that an expert on rocket fuel might forget something like surface area of a catalyst throwing off his rate of reaction.
May 18, 2010 at 9:30 am
Maybe Sheldon was looking up his candidate roommate’s research before he showed up.
May 18, 2010 at 1:03 pm
Brilliant, that would indeed be so Sheldon.
July 30, 2010 at 2:33 pm
Oh Sheldon, Mr know it all. Yet we still love him….
July 15, 2010 at 11:17 pm
Really? How could a scientist really make a mistake like this? Imagine if he actually had to do that for a real space ship….It really does prove that Sheldon was always right though.His work is always based off someone else’s….After all he could not even change one small part of the formula properly
May 18, 2010 at 5:50 am
As a chemist, I’m ashamed to say I missed the white board equations. But I did catch a chemical mispronunciation, thereby partially redeeming myself. When Leonard came back from polishing Penny’s toenails, sheldon asked why he smelled of “methacrylate,” pronouncing it meth-uh-CRI(long i)-late. It’s meth-A(short a as in “cat”)-cri (short i)-late.
May 18, 2010 at 11:18 am
Merriam-Webster Online:
Main Entry: meth·ac·ry·late
Pronunciation: \ˌme-ˈtha-krə-ˌlāt\
Function: noun
Etymology: International Scientific Vocabulary
Date: 1865
1 : a salt or ester of methacrylic acid
2 : an acrylic resin or plastic made from a derivative of methacrylic acid
May 19, 2010 at 9:44 pm
Agreed.
May 18, 2010 at 8:21 am
I know it’s not science related, but why are Raj and Howard dressed so differently when Sheldon and Leonard are dressed the same? As the post above notes, the back story is from 2003, not 1983. Just curious.
May 19, 2010 at 8:40 pm
It was a joke. Another series made the same one. Clerks Animated Series.
The flashback episode showed them like 10 years prior and they looked exactly the same. One of the made the comment that “I can’t believe we looked like that. Look at our hair”
May 18, 2010 at 12:05 pm
When have either Raj or Howard had any fashion sense? They have always been close to a decade behind in fashion. I thought it was kind of cute how they were dressed. Even though Raj did look like he time traveled right out of the 80’s.
And speaking of time travel I though that the moment Sheldon and Leonard took to see if they would come walking through the door after they initialed the time travel paragraph was priceless!
May 18, 2010 at 5:28 pm
I too thought the moment they looked around, hoping to see their future selves materialize, was one of the sweetest AND funniest I’ve ever seen on TV – and I could definitely see myself doing the same thing. Awesome writing and acting!
May 19, 2010 at 2:19 pm
We found it difficult to believe that a North Korean spy would be dissuaded so easily.
May 19, 2010 at 8:34 pm
You made a bigger mistake.
The PS2 slimline model shown in the ep, came out a year after the date in the flashbacks
http://en.wikipedia.org/wiki/PlayStation_2#Slimline
May 19, 2010 at 8:43 pm
I’m just a science geek not a geekdom geek. If I were to guess though, I wouldn’t put it past the guys to have scored a prototype.
May 21, 2010 at 2:32 am
While the existence of a prototype a year and a half before release is unlikely, I’ll let it slide cause of how awesome they are. Love the show.
May 19, 2010 at 9:04 pm
Didn’t anyone else think it was odd that an Experimental physicist who tests theories via designing experiments was doing Applied physics reasearch? Particularly in a domain reserved mostly for Chemical physics/Physical chemistry?
May 19, 2010 at 9:40 pm
It was seven years ago. Physicists are flexible enough to move between fields. Especially early in their careers.
September 26, 2010 at 8:33 pm
Hydrazine is not used as an auxiliary power source aboard the International Space Station.
In terms of energy the ISS is a pure solar-powered electrical vehicle with the giant solar arrays generating a whole lot of power. To a very tiny degree that’s supplemented with small off-the-shelf batteries (used for some stand-alone experiments), off-the-shelf rechargeable batteries (for power tools, camcorders and similar devices), the batteries aboard the Russian Soyuz and Progress spacecraft, and occasionally the space shuttle’s fuel cells when it’s docked (as often as not the space station actually powers the space shuttle while it’s docked through a set of fancy jumper cables so the shuttle can save its fuel cells for the journey home).
In terms of propulsion the rocket engines use monomethyl hydrazine as the fuel and nitrogen tetroxide as the oxidizer. Normally the Russian Progress spacecraft is used to boost the orbit (to make up for the drag from the Earth’s upper atmosphere and for orbital adjustments) although this task can also be performed by the European Automated Transfer Vehicle (ATV) and Space Shuttle.
Hydrazine is used for auxiliary power in the Hydraulic Power Units which steer the space shuttle’s solid rocket boosters and in three auxiliary power units (APU) in the aft end of the shuttle. During launch the APUs are used to steer the shuttle’s main engines, during entry they’re used to move the elevons and rudder.
February 28, 2011 at 7:46 pm
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