• Content count

  • Joined

  • Last visited

Community Reputation

39 Excellent

About totalitor

  • Rank
    SSTO for fun
  1. Check this out I am using this in my project.
  2. What do you think?
  3. Atlas, rise! Is James Hetfield buying Atlas?
  4. Indeed, me too. Would be interesting.
  5. Thank you for your answers. I was thinking small, something like this: If I build a rocket 1 meter height (3 feet) and I use liquid oxygen and kerosine. Just thinking if there is enough benefit not to insulate. Weight saving would be...1 kg? Max? Is it worth? I guess not. Is it possible to use liquid oxygen boiloff instead of pressure feeding system using nitrogen or helium? Weight saving you know...
  6. What if there is no insulation on cryogenic rocket? I know liquid oxygen would boil off but how fast? What if that rocket would be kept on container below boiling point? When fuelled and ready to launch container roof would go away and rocket would be launched. No time to boil off until the rocket is flying. A rocket small enough and fuel lets say to one minute burning - how much weight saving is possible? Or does liquids boil off too much? Think small, not big. Is this idea doomed? Are there rockets using liquid oxygen without insulation (Copenhagen Suborbital Nexo I has no insulation when flying)?
  7. RUD-2 construction failed. I decided to build a bigger engine. RUD-3 is ready Thrust: 14,35 lb (63,9 N) Isp using gaseous oxygen and 75 % alcohol about 240 so total mass flow 0,0598583 lb/sec (27,151 g/s). Mixture ratio 1.25, chamber pressure 300 psi, so fuel flow 0,0266036 lb/sec (12,067 g/s) and oxygen flow 0,0332546 lb/sec (15,084 g/s). Pressure on throat 169,2 psi, Diameter of throat 0,2 inch (5,09 mm) Chamber diameter is 0,6299 inch (16 mm) Exit diameter 0,382 inch (9,7 mm) Lenght about 4,6 inch (11,7 cm) Fuel orifice diameter 0,031 inch (0,8 mm) Oxygen orifice 0,116 inch (3 mm) I guess success in building RUD-1 was just luck. With this engine I had great difficulties in final brazing. I made two attempts and when ready fuel orifice was stucked. I had to dig feeding lines open and try again. Third time was success. My equipment cannot handle building bigger than this, brazing operation needs heating power that I don't have. And designing needs rethink, what looks easy in paper is not in practice. What next? Where I live winter is coming, I cannot do things becouse I do everything outside. Coldness stops everything. I design other components in winter and do them next summer. Maybe test firing is then. Please feel free to comment my project.
  8. I can really now see difficulties of building such a small engine. My injector consist of one oxygen hole and one fuel hole. I calculated that fuel velocity would drop from 1189 inch/s to 153 inch/s if I use 0,8 mm hole instead of 0,3 mm hole. That's bad I guess. Ok new try with 0,3 mm hole and I definetly need a good fuel filter. Sorry if I use SI-units and imperial units together...
  9. I was drilling 0,3 mm hole to coppertube. It did work, but when I was brazing things together that hole was blocked. Maybe brazing material melt. It was not anymore visible so I have to change way of putting things together. What if I use 0,8 mm hole for fuel (my calculations says it should be 0,3 mm)? Oxygen hole is 1 mm according calculations. Chamber pressure estimated 300 psi. Is it too fuel-rich? What will happen?
  10. If the first weird voice was some part separated from rocket and the second was that part hitting the pad? Time between those voices is about 2 s so that part came down from 20 metres. What is on that location?
  11. The speed of cooling liquid should be the same from nozzle to exit point and to maintain the same speed cooling flow area should be the same. But there is that de laval nozzle. In my design smallest diameter of the outer skin combustion chamber would be 6 mm (about 2,5 mm inside is the throat diameter). Elsewhere diameter would be 8 mm. Instead of curving outer cooling tube, what if I fill that curve with copper? I would have 3 mm layer of copper there instead of tube thickness 0,8 mm. The engine would be easier to make becouse no curving of outside cooling tube would be needed. What would happen?
  12. ap0r - that equation no 25. There is a number 6430 on that example. Where does it come from? I GOT IT! 100 psi is 14400 lbs/ft^2 ... had to convert it.
  13. Calculating...tell me if I go wrong. Expected thrust 2 lb. I use the same book and formulas that ap0r uses. Isp using gaseous oxygen and 75 % alcohol about 240 so total mass flow 0,00833 lb/sec. Mixture ratio 1.25, chamber pressure 300 psi, so fuel flow 0,0037022 lb/sec and oxygen flow 0,0046278 lb/sec. Pressure on throat 169,2 psi, Throat area 0,0043913 inch^2. This was hard. Need info about molecular weight of gas. Diameter of throat 0,0747741 inch (1,8993 mm so my first RUD-1 throat is too big). Guessing value L? Make a guess between 50-100? I make 50 so chamber volume is 0,219565 inch^3. Diameter of chamber should be 3-5 x throat diameter. I use value 3,37 so chamber diameter is 0,25197 inch (6,4 mm) Lenght of chamber is 4 inch (10,16 cm). Looks weird. RUD-1 is too small I guess. And hole for fuel injector 0,0113232 inch (0,28761 mm) and if I want two holes even smaller...a big problem. Oxygen hole 0,0432435 inch (1,0984 mm) - no problem.
  14. You are exactly right. Still, I do it my way...
  15. I use "How to design small rocket engines" book for insructions. I took there example and made 1/10 size of that (chamber lenght is just guessing). Example engine thrust is 20 pounds and chamber pressure is 300 psi. I don't know how those scale, maybe thrust in my engine is 2 pounds but I don't know about chamber pressure. Maybe that is the same? Fuel and oxygen flow rates will also be 1/10. I will make different versions becouse fabrication is so easy, one day for an engine. And it is not expensive.