SDS

Liquid-Nitrous-Oxide, Temperature-Pressure-Density table from Friends of Amateur Rocketry

Linde Sponsorship

Contact: Derek Breitenstine, Derek.Breitenstine@linde.com

Keira Boone (kboone@mit.edu) and Reva Mathankar are both within an email thread from February 9, 2026 where Linde agreed to sponsor us in the form of providing N2O free of charge to the team. As of May 2026, we are planning to reach back out at the end of summer to follow up, but know that this is a possibility.


ORDER WITH A SIPHON TUBE

After three failed hotfire attempts at bluShift in 2025-2026, we learned the main reason: it turned out we'd been filling with gaseous nitrous this whole time, because there was a typo in the order. The order should've been NS RF 64S, but instead NS RF 64 was ordered which is very conveniently a nitrous tank with no siphon tube. YOU NEED A SIPHON TUBE FOR LIQUID NITROUS!!!

Because we still had 3 full cylinders of gaseous nitrous with no siphon tube, we made a quick 80/20 structure (see below) and just put that at the bottom of the gas cylinder cart so that the liquid is at the bottom (since there is no siphon tube). 

photo of 80/20 structure on its own, then with the bottle on the cart on its side, then flipped to be added

           How a siphon tube works:

A metal tube is attached to the valve and extends down to the lowest point of the bottle, and when the valve is opened, the high internal pressure (roughly 900) psi) forces the liquid nitrous up the tube and out of the valve, allowing the bottle to be used while standing upright. To work correctly, the siphon tube must be lined up with the outlet port so it points toward the bottom-rear of the bottle.


Note that some liquid may allow a successful fire at first even without a siphon tube. (deprecated)

If a non-siphon bottle is used, it typically dispenses gaseous nitrous because it draws from the top space. However, liquid can come out initially due to a few factors, and our current working theories are:

  • Linde may slightly overfill their bottles
  • There may be a partial siphon tube or fitting that goes partway down the bottle; 
  • Cold/High Pressure: If the tank is full and very cold, the internal pressure can fluctuate.
  • Sloshing or Inversion: If the bottle was tilted, moved, or partially inverted, the liquid inside can cover the outlet port, causing liquid to be pushed out instead of gas.
  • Excessive Flow Rate: Opening the valve too quickly can cause a rush of liquid, especially if the tank is very full


Note that some gaseous nitrous may allow for successful ignition at first, but it cannot sustain ignition.

If the tank is accidentally filled with gaseous nitrous, there are a few easy ways to tell. 

  • Unexpectedly low pressure drop across fluid lines and valves
    • Actually unclear about this one – theory would predict this but data shows on the order of ~30 psi of pressure drop across our system regardless of liquid or gaseous nitrous
  • Unexpectedly high nitrous vapor pressure
    • The system is designed so that some gaseous nitrous vents from the nitrous tank when filling. The boiloff of liquid nitrous that replaces the lost gas takes away heat, which cools the nitrous and lowers the vapor pressure. When filling with gaseous nitrous, this effect isn't as strong. We saw ~500 psi of nitrous tank pressure after filling with gaseous nitrous and ~400 psi of nitrous tank pressure after filling with liquid, under similar weather conditions. The exact final pressure after the fill is dependent on the fluids system, fill procedure, and ambient temperature, but it should be possible to tell the nitrous phase just from the vapor pressure after fill alone.
  • No nitrous pressure recovery after vent/fire attempt
    • After opening a vent valve or attempting to hotfire, if there is still liquid nitrous left in the tank, the tank pressure should be at least the nitrous vapor pressure. However, if the tank is accidentally filled with gaseous, the pressure will not recover.


Gerard Desjardins' Bottle Opening Technique

Disclaimer: bluShift engineers do this for us, and it is something they are comfortable doing. 

Gerard is the Lead Propulsion Test Engineer at bluShift, and he will crack the cap of the cylinder and (pointing it away from himself) open the valve to see a plume, at which point it is visually identifiable whether the plume is liquid or gas.  Note that is is NOT OBVIOUS if you have not seen it before.

GASEOUS                                                                    LIQUID



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