I amongst others have posted on the site but our thoughts and questions are unanswered. If you don’t have the resources it is probably better to remove the option.
I put these thought on a few weeks ago,
Otherwise great site and I wish you well.
john ashcroft · 7th March 2021 at 6:06 pm
There maybe an easier way of pressurising the system. I don’t know if it will be lighter but should be simpler and lower cost.
You are looking at using a low performance rocket to vaporise and heat your rocket; I am going to suggest a different low performance rocket, taking a few ideas from Robert Truax
Have you considered a “hot water rocket”?
Essentially Water is superheated, probably resistively in a simple carbon steel tank. It can then be used to vaporise LOX directly, or could be used to pressurise and vaporise LN2. Pressurised LN2 could be vaporised by passing through etoh. (similar to Sea Dragon, though methane to pressurise RP-1)
Vaporized LOX or LN2 can be heated to 373K by direct injection of superheated water to the gas in the tanks. Not required for simple engine testing but should lower pressurant mass in rocket.
If you drop me an email I can run some numbers past you.
REPLY
john ashcroft · 13th March 2021 at 6:39 pm
Some numbers: To vaporise 32kg of LOX to pressurise the LOX tank would require some 11kg of superheated water at 240C, 33bar. Tank maybe 8kg.
Some could be used to vaporise/pressurise tank of LN2, you would need 25kg of LN2 in a tank maybe 17kg, to be jetted into the etoh/water tank, vaporising/pressurising.
Using superheated water to heat presurants in tanks to 373 would save some weight but would add complexity.
john ashcroft
· 9th April 2021 at 3:19 pm
Many thanks,
your numbers on the mass of superheated water are similar to mine, about 11kg.
The tanks look heavy though, and I think it is because you need to look at the LN2 tanks differently for this concept.
It looks like you have the the LN2 in a pressurised tank already, I presume at 33 bar? This is significantly higher than the tank pressure so I presume this is the pressure in the LN2 tank working in a blow down mode to feed the heater? (33bar approximately the critical pressure for LN2). Simple but it has its consequences.
This means the LN2 is much less dense than at boiling point at atm. (500g/l vs 800g/l)
This leads to a bigger and hence heavier tank, and also the pressure of the tank at 33bar is 50% higher than needed if vaporised by hot water.
The combined effect is a LN2 tank that is over 50% bigger and more than twice as heavy (the LN2 tank is maybe 38-40kg?) than is needed for the concept of heating with hot water. (And you only need it for the fuel tank pressurisation.)
I suggest you look at Air Lift tanks. Seamless aluminium rated for 200PSI have burst pressures of 750PSI, very cheap, should be OK for cryogenic LN2 being vaporized at 20bar.
For 25kg LN2 at atm, 30liters
A 4gallon, 16l tank is about 4kg. https://www.limebug.com/product/view/3645/50-gallon-moa-seamless-aluminium-air-tank-5x-npt-ports-200-psi-rated-509.
So for LN2 tanksX2 =8kg, or maybe 30kg less than your LN2 tanks at present?
For the hot water tank you need start pressure of maybe 30bar, 400PSI 225C pressure drop about 25% to empty. https://rocketbelts.americanrocketman.com/steam.html (Bob Traux Paper)
Aluminium should still be OK at this temperature but there are stainless steel air lift tanks with higher burst pressures (1200PSI+).
john ashcroft
· 7th April 2021 at 1:49 pm
Many thanks,
your numbers on the mass of superheated water are similar to mine, about 11kg.
The tanks look heavy though, also you need to look at the LN2 tanks differently for this concept.
I presume you have the the LN2 in a pressurised tank already? And probably at some pressure, 33 bar is significantly higher than the tank pressure so I presume this is the pressure in the LN2 tank working in a blow down mode to feed the heater? (33bar approximately the critical pressure for LN2)
This means the LN2 is much less dense than at boiling point at atm. (500g/l vs 800g/l)
This leads to a heavier tank, and also the pressure of the tank at 33bar is 50% higher than needed. The LN2 tank is are maybe 38-40kg?
The combined effect is a LN2 tank that is over 50% bigger and more than twice as heavy as needed, (And you only need it for the fuel tank pressurisation.)
I suggest you look at Air Lift tanks. Seamless aluminium rated for 200PSI have burst pressures of 750PSI, very cheap, should be OK for cryogenic LN2 being vaporized at 20bar.
For 25kg LN2 at atm, 30liters
A 4gallon, 16l tank is about 4kg. https://www.limebug.com/product/view/3645/50-gallon-moa-seamless-aluminium-air-tank-5x-npt-ports-200-psi-rated-509.
So for LN2 tanksX2 =8kg, or maybe 30kg less than your LN2 tanks at present?
For the hot water tank you need start pressure of maybe 30bar, 400PSI 225C pressure drop about 25% to empty. https://rocketbelts.americanrocketman.com/steam.html (Bob Traux Paper)
Aluminium should still be OK at this temperature but there are stainless steel air lift tanks with higher burst pressures (1200PSI+).
The LOX tank needs to be slightly bigger for the LOX that will be used as pressurant
.It should be possible to have most of the hot water be retained in the LOX as it vaporises it as ICE. So slightly less water in the fuel.
T
john ashcroft
· 8th April 2021 at 2:18 pm
Many thanks,
your numbers on the mass of superheated water are similar to mine, about 11kg.
The tanks look heavy though, also you need to look at the LN2 tanks differently for this concept.
I presume you have the the LN2 in a pressurised tank already? And probably at some pressure, 33 bar is significantly higher than the tank pressure so I presume this is the pressure in the LN2 tank working in a blow down mode to feed the heater? (33bar approximately the critical pressure for LN2)
This does means the LN2 is much less dense than at boiling point at atm. (500g/l vs 800g/l)
This leads to a bigger, heavier tank, and also the pressure of the tank at 33bar is 50% higher than needed if vaporised by hot water.
The combined effect is a LN2 tank that is over 50% bigger and more than twice as heavy than is need this concept of vaporising directly in the tank with hot water. This is significant because the LN2 tank is maybe 38-40kg?)
You also only need the LN2 to pressurise the fuel. You can use the hot water to vaporise the LOX directly.
I suggest you look at Air Lift tanks. Seamless aluminium rated for 200PSI have burst pressures of 750PSI, very cheap, should be OK for cryogenic LN2 being vaporized at 20bar.
For 25kg LN2 at atm, 30liters
A 4gallon, 16l tank is about 4kg. https://www.limebug.com/product/view/3645/50-gallon-moa-seamless-aluminium-air-tank-5x-npt-ports-200-psi-rated-509.
So for LN2 tanks for fuel pressurisation you would need 2x 4kg tanks= 8kg.
For the hot water tank you need start pressure of maybe 30bar, 400PSI 225C pressure drop about 25% to empty. https://rocketbelts.americanrocketman.com/steam.html (Bob Traux Paper)
Aluminium should still be OK at this temperature but there are stainless steel air lift tanks with higher burst pressures (1200PSI+).
The LOX tank needs to be slightly bigger for the LOX that will be used as pressurant.
Comments are closed.
We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.OkRead more
4 Comments
john ashcroft · 2nd April 2021 at 6:00 pm
I amongst others have posted on the site but our thoughts and questions are unanswered. If you don’t have the resources it is probably better to remove the option.
I put these thought on a few weeks ago,
Otherwise great site and I wish you well.
john ashcroft · 7th March 2021 at 6:06 pm
There maybe an easier way of pressurising the system. I don’t know if it will be lighter but should be simpler and lower cost.
You are looking at using a low performance rocket to vaporise and heat your rocket; I am going to suggest a different low performance rocket, taking a few ideas from Robert Truax
Have you considered a “hot water rocket”?
Essentially Water is superheated, probably resistively in a simple carbon steel tank. It can then be used to vaporise LOX directly, or could be used to pressurise and vaporise LN2. Pressurised LN2 could be vaporised by passing through etoh. (similar to Sea Dragon, though methane to pressurise RP-1)
Vaporized LOX or LN2 can be heated to 373K by direct injection of superheated water to the gas in the tanks. Not required for simple engine testing but should lower pressurant mass in rocket.
If you drop me an email I can run some numbers past you.
REPLY
john ashcroft · 13th March 2021 at 6:39 pm
Some numbers: To vaporise 32kg of LOX to pressurise the LOX tank would require some 11kg of superheated water at 240C, 33bar. Tank maybe 8kg.
Some could be used to vaporise/pressurise tank of LN2, you would need 25kg of LN2 in a tank maybe 17kg, to be jetted into the etoh/water tank, vaporising/pressurising.
Using superheated water to heat presurants in tanks to 373 would save some weight but would add complexity.
john ashcroft · 9th April 2021 at 3:19 pm
Many thanks,
your numbers on the mass of superheated water are similar to mine, about 11kg.
The tanks look heavy though, and I think it is because you need to look at the LN2 tanks differently for this concept.
It looks like you have the the LN2 in a pressurised tank already, I presume at 33 bar? This is significantly higher than the tank pressure so I presume this is the pressure in the LN2 tank working in a blow down mode to feed the heater? (33bar approximately the critical pressure for LN2). Simple but it has its consequences.
This means the LN2 is much less dense than at boiling point at atm. (500g/l vs 800g/l)
This leads to a bigger and hence heavier tank, and also the pressure of the tank at 33bar is 50% higher than needed if vaporised by hot water.
The combined effect is a LN2 tank that is over 50% bigger and more than twice as heavy (the LN2 tank is maybe 38-40kg?) than is needed for the concept of heating with hot water. (And you only need it for the fuel tank pressurisation.)
I suggest you look at Air Lift tanks. Seamless aluminium rated for 200PSI have burst pressures of 750PSI, very cheap, should be OK for cryogenic LN2 being vaporized at 20bar.
For 25kg LN2 at atm, 30liters
A 4gallon, 16l tank is about 4kg. https://www.limebug.com/product/view/3645/50-gallon-moa-seamless-aluminium-air-tank-5x-npt-ports-200-psi-rated-509.
So for LN2 tanksX2 =8kg, or maybe 30kg less than your LN2 tanks at present?
For the hot water tank you need start pressure of maybe 30bar, 400PSI 225C pressure drop about 25% to empty. https://rocketbelts.americanrocketman.com/steam.html (Bob Traux Paper)
Aluminium should still be OK at this temperature but there are stainless steel air lift tanks with higher burst pressures (1200PSI+).
john ashcroft · 7th April 2021 at 1:49 pm
Many thanks,
your numbers on the mass of superheated water are similar to mine, about 11kg.
The tanks look heavy though, also you need to look at the LN2 tanks differently for this concept.
I presume you have the the LN2 in a pressurised tank already? And probably at some pressure, 33 bar is significantly higher than the tank pressure so I presume this is the pressure in the LN2 tank working in a blow down mode to feed the heater? (33bar approximately the critical pressure for LN2)
This means the LN2 is much less dense than at boiling point at atm. (500g/l vs 800g/l)
This leads to a heavier tank, and also the pressure of the tank at 33bar is 50% higher than needed. The LN2 tank is are maybe 38-40kg?
The combined effect is a LN2 tank that is over 50% bigger and more than twice as heavy as needed, (And you only need it for the fuel tank pressurisation.)
I suggest you look at Air Lift tanks. Seamless aluminium rated for 200PSI have burst pressures of 750PSI, very cheap, should be OK for cryogenic LN2 being vaporized at 20bar.
For 25kg LN2 at atm, 30liters
A 4gallon, 16l tank is about 4kg. https://www.limebug.com/product/view/3645/50-gallon-moa-seamless-aluminium-air-tank-5x-npt-ports-200-psi-rated-509.
So for LN2 tanksX2 =8kg, or maybe 30kg less than your LN2 tanks at present?
For the hot water tank you need start pressure of maybe 30bar, 400PSI 225C pressure drop about 25% to empty. https://rocketbelts.americanrocketman.com/steam.html (Bob Traux Paper)
Aluminium should still be OK at this temperature but there are stainless steel air lift tanks with higher burst pressures (1200PSI+).
The LOX tank needs to be slightly bigger for the LOX that will be used as pressurant
.It should be possible to have most of the hot water be retained in the LOX as it vaporises it as ICE. So slightly less water in the fuel.
T
john ashcroft · 8th April 2021 at 2:18 pm
Many thanks,
your numbers on the mass of superheated water are similar to mine, about 11kg.
The tanks look heavy though, also you need to look at the LN2 tanks differently for this concept.
I presume you have the the LN2 in a pressurised tank already? And probably at some pressure, 33 bar is significantly higher than the tank pressure so I presume this is the pressure in the LN2 tank working in a blow down mode to feed the heater? (33bar approximately the critical pressure for LN2)
This does means the LN2 is much less dense than at boiling point at atm. (500g/l vs 800g/l)
This leads to a bigger, heavier tank, and also the pressure of the tank at 33bar is 50% higher than needed if vaporised by hot water.
The combined effect is a LN2 tank that is over 50% bigger and more than twice as heavy than is need this concept of vaporising directly in the tank with hot water. This is significant because the LN2 tank is maybe 38-40kg?)
You also only need the LN2 to pressurise the fuel. You can use the hot water to vaporise the LOX directly.
I suggest you look at Air Lift tanks. Seamless aluminium rated for 200PSI have burst pressures of 750PSI, very cheap, should be OK for cryogenic LN2 being vaporized at 20bar.
For 25kg LN2 at atm, 30liters
A 4gallon, 16l tank is about 4kg. https://www.limebug.com/product/view/3645/50-gallon-moa-seamless-aluminium-air-tank-5x-npt-ports-200-psi-rated-509.
So for LN2 tanks for fuel pressurisation you would need 2x 4kg tanks= 8kg.
For the hot water tank you need start pressure of maybe 30bar, 400PSI 225C pressure drop about 25% to empty. https://rocketbelts.americanrocketman.com/steam.html (Bob Traux Paper)
Aluminium should still be OK at this temperature but there are stainless steel air lift tanks with higher burst pressures (1200PSI+).
The LOX tank needs to be slightly bigger for the LOX that will be used as pressurant.
Comments are closed.