Breaking Bad rocket style: Cooking fuel in a trailer lab

They said buying propellant would be the easy part. Considering our thick accent and brief history in the Space industry we also chose chemicals allegedly simple and cheap to acquire: nitric acid and furfuryl alcohol, not perfect but close to our Mars propellant plan. Well, here is how we went from placing an easy order to cooking our own rocket fuel.

"Christ, they even have a yellow RV!" Caught up in work we rarely watch entertainment lately and until last month, we had never seen Breaking Bad. By strange providence, the series came to our attention just as we were about to cook rocket fuel in our 80s camper. We binge-watched the show for a week straight.

Sierra Nevada is a great place to work and play. Skiing kept open until last weekend. Our final turns went alongside future Olympians training on the last snow and a handful of ski bums living out of their vans.  

In the village, a yearly motocross race is setting up. The riders have some serious plumbing solutions that we plan to check out for our upcoming engine hot test.

A local rodeo reminded of the ways of the great Wild West, a spirit we felt close to as we unpacked our flasks deep in the forest.

Homeland Security

Nitric acid and furfuryl alcohol are perfectly legal to own and make in the US. It's also legal to own laboratory distilling equipment (unless you use it for moonshine). It just doesn't feel legal.

Especially if you do it in a camper tucked away by a stream on a mountain pass.  It may also prove hard to convince the sheriff right away.

Turns out that after 9/11 Homeland Security seems to have every single chemical on the terrorism list (DHS anti-terrorism chemicals of interest list).

For Nitric Acid, our oxidizer, that also includes anything stronger than 68%, while we need 95-99% for a good thrust.

Rocket friends down in Mojave told us the concentrated stuff can be had with some paperwork, but the transportation would be hugely expensive - around $10k for even a small volume. A workaround, they said, is to get the 68% and vacuum distill it up to 95%.

The propellant we need is hypergolic (self-igniting) but not explosive, and environment-friendly to boot. Yet even for the 68% nitric acid version, our purchase request was met with loads of questions and requirements. You can buy drugs easier than that. Sadly for citizen science; it was a no-go.

Or was it.

The chemical formula for nitric acid is HNO3. That's a  bit of hydrogen, a bit of nitrogen and a bigger bit of oxygen. These are three of the most common elements in the universe. How hard could it be to cook up the nitric acid from scratch?

This is how we went Breaking Bad.

Rocket fuel 2018: Youtube University and Amazon.com

We dove into research. Potassium nitrate and sulfuric acid, mixed and heated to 82C, would supposedly yield nitric acid 95% or higher.

But where to get potassium nitrate and sulfuric acid? Google offered more help: Household products.

Potassium nitrate is used to dissolve tree stumps and sulfuric acid is used to unclog pipes and clean drains. Not all brands work but all, including the good stuff, are available at Amazon.

Following a crash course in lab equipment, we ended up ordering

- 2 x 500 ml boiling flasks,

- a Liebig condenser,

- a 3-way distillation adapter

...plus other bits and ends needed for distillation, including a small $8 fish tank pump for water cooling.

Being on a budget we didn't want to shell out $100 for a Bunsen burner so we made one out of an old camping stove and an empty tomato can. A wind shelter at the back of our camper and we were in business.

Cooking the test batch

Cooking rocket fuel is just like cooking food. The greatest chefs are very exact with temperatures and amounts of ingredients.

The stoichiometric formula (balance) for our brew looks like this:

KNO3 + H2SO4 => HNO3 + KHSO4

or

stump remover + drain cleaner => rocket propellant + stuff we don't need.

The secret sauce is the temperature. At 82 degrees C, the stump remover and drain cleaner marry and make nitric acid which wanders off as vapor through the glass pipes.  It cools to a liquid form; of almost pure nitric acid.

Nitric acid can go bad (it decomposes) in direct sunlight and high temperature, so we didn't want to overheat.

Cooking meals high up on Everest, we knew that low air pressure lowers the boiling temperature, so we controlled for our current altitude. To our surprise, at 2500 meters, the boiling temperature for nitric acid actually went down to 72C.

Safety

Commonly used in the horrible act of "acid throwing", sulfuric and nitric acid give terrible burns and can lead to permanent blindness.

Eye protection is a given but concentrated nitric acid reacts badly with plastic, so we removed our gloves at that stage of the process. The acids can be neutralized with a base (baking powder) and diluted with water.

Having scaled high mountains, skied to the poles, sailed across big oceans, and built businesses on two continents - we were remarkably nervous as we assembled our glassware and got ready for the first batch.

We measured up the ingredients and put a lighter to our homemade burner.

The thermometer started to climb. At exactly 72 C the first vapor formed in the Liebig condenser. We jumped up. The next minute a first drop of nitric acid formed. We stared at it in awe. An hour later we had made 25 ml of what looked like pale liquid gold.

Testing the rocket propellant

It was an unexpected success. But how concentrated was it? We performed a few tests. Blowing air into the liquid resulted in white fumes, indicating white fuming nitric acid which can only exist above 95%. Good start.

We dropped a piece of copper inside. A brief reaction indicated a very high concentration.

We diluted the liquid with water. As predicted, a violent, purple reaction and one minute later the copper was completely gone. Clearly, we had made some potent stuff.

But is it hypergolic?

Time for the final test. To check if our oxidizer (nitric acid) would ignite the fuel we performed an open cup experiment.

As a rocket fuel, turpentine has similar properties to furfuryl, so we got some of that. In our firepit, we added 10 ml of nitric acid in a cup and then a couple of drops of turpentine with a pipette. Whoa! We jumped back. An intense fire plume shot up in the air.

We had created our own, hypergolic rocket propellant.

Scaling for Mojave - 40 hours

We will need about 10 liters of the oxidizer (nitric acid) for our first engine firing in Mojave this summer (10-second burn with 5000 Newton thrust).

Upgrading to a 5000 ml boiling flask we could cook 10 liters of nitric acid in 40 hours. Two setups and we are done in less than a day. The cost will be around $800, or even below $300 with cheaper suppliers of drain cleaner and stump remover that we have found.

Scaling for Mars - 1 month

Taking off from Mars surface to the orbiting Mothership, our MAV  will have a dry weight of 710 kg and need 1500 liters of oxidizer. If we used nitric acid and 10 of the above distillation setups we could make 1500 liters in 600 hours - or less than a month.

That's not how we'll do it, there are much more effective ways, but still, good to know at this stage.

On Mars we will actually use MMH and NTO for propellant. Nitric acid and furfuryl/turpentine are great substitutes during tests of the rocket engines: Less toxic and less restrictions, but still storable and hypergolic.