1. Toshiyuki KATSUMI and Keiichi HORI(ISAS/JAXA)
HAN based green propellant - Application and its Combustion Mechanism -
Toshiyuki KATSUMI
and Keiichi HORI(ISAS/JAXA) 1

2. HAN-based liquid propellant
Hydroxyl Ammonium Nitrate (NH2OH･HNO3)
High Oxidizability
Low Toxicity
High Deliquescent
Water Solution
Liquid Oxidizer
Monopropellant
High Density
Low Freezing Point

3. Comparison of HAN-based solution with Hydrazine
HAN-based propellant
(SHP163)
Density ρ [×103 kg/m3] at 20 ˚C
1.0
1.4
Freezing temperature [˚C]
-68
Specific Impulse Isp** [s]
233
276
ρ･Isp** [×103 s*kg/m3]
386
Toxicity
High
Low
* SHP163: HAN/Ammonium Nitrate/Water/Methanol=95/5/8/21 (mass ratio)
** Nozzle area ratio (Ae/At);50, CF;1.875, Combustion chamber pressure; 0.7MPa
ρ･Isp of HAN-based propellant is approximately 70% higher than Hydrazine

4. Burning rate Combustion mechanism has not been clarified
Control HAN/AN/Water/Methanol = 95/5/8/0
SHP069 HAN/AN/Water/Methanol = 95/5/8/8
SHP163 HAN/AN/Water/Methanol = 95/5/8/21
Control
SHP069
Control
Control
SHP069
SHP163
Combustion mechanism has not been clarified
AN and methanol are eliminated
Hydrodynamic instability triggers the jump of the burning rate to very high rate region
Methanol addition shifts the critical pressure to higher pressure.

5. Burning rates of aq. solutions
80mass%
82.5mass%
77.5mass%
64mass%*
64mass%
85mass%
50mass%
The linear burning rate has the peak at approximately 80mass% of HAN concentration
Crystal*
95mass%
*B. N. Kondrikov, V. E. Annikov, V. Yu. Egorshev, and L. T. De Luca,
“Burning of Hydroxylammonium nitrate”, Combustion, Explosion and Shock waves, Vol.36,No.1 ,2000 5

6. The linear burning rates are classified to three zones
High burning rate
The linear burning rates are classified to three zones
Zone2
Zone3
Zone1
Low burning rate 6

7. Combustion model of HAN aqueous solution
Objective
Combustion model of HAN aqueous solution
Combustion Model of HAN-based propellant solution 7

8. The combustion wave structure of HAN aq. solution
95mass% solution
80mass% solution
Reaction zone Tf
Tbp
Tbp T T
Liquid phase
Gas phase
Two-phase
Liquid phase
Two-phase 8 8

9. The combustion wave structure of HAN aq. solution
95mass% solution
80mass% solution
Reaction zone
Reaction zone Tf
Tbp
Tbp T T
Liquid phase
Gas phase
Two-phase
Liquid phase
Two-phase
Combustion wave structure changes by the water content 9 9

10. High rb mode Two-phase region
Reaction zone
High rb mode
Two-phase region
Fine bubbles are generated in front of the combustion wave
Chemical reaction starts in the bubble
Two-phase
Liquid phase 10

11. High rb mode Two-phase region dT
Reaction zone
High rb mode
Two-phase region
Fine bubbles are generated in front of the combustion wave
Chemical reaction starts in the bubble
Significant superheat (dT) is generated
Two-phase
Liquid phase dT 11

12. High rb mode Two-phase region dT
Reaction zone
High rb mode
Two-phase region
Fine bubbles are generated in front of the combustion wave
Chemical reaction starts in the bubble
Significant superheat (dT) is generated
Rapid nucleation is caused by superheat
Two-phase
Liquid phase dT 12

13. Nucleation rate may determine the burning rate
Reaction zone
Two-phase
Liquid phase
High rb mode
Two-phase region
Fine bubbles are generated in front of the combustion wave
Chemical reaction starts in the bubble
Significant superheat (dT) is generated
Rapid nucleation is caused by superheat
High rb mode is established
Nucleation rate may determine the burning rate 13 13

14. Superheat & Nucleation rate
DT; superheat
Tg; vapor temperature
TSAT; saturation temperature
dn/dt; nucleation rate
N; number of molecules
per unit volume
k; Boltzmann constant
h; Plank’s constant
r*; radius of the vapor nucleus
s; surface tension
R; universal gas constant
ifg; latent heat of vaporization
M; molecular weight
pf; pressure in liquid space
Liquid
Bubble Tg
TSAT , 14

15. Radiuses of vapor nucleuses
Parameter;
Pressure1~8MPa
Gas temperature
800~1300K
r*min=2x10-9m
(10A) 15

16. Nucleation rate (dn/dt)
r*min=2x10-9m
Parameter;
Pressure1~8MPa
Gas temperature
800~1300K 16

17. In Zone2, bubble nucleation rate governs the burning rate.
dv/dt (4/3pr*3dn/dt)
Linear burning rate
1000mm/s
1mm/s
In Zone2, bubble nucleation rate governs the burning rate.
80mass%
77.5mass%
82.5mass%
64mass%
50mass% 17 17

18. dv/dt (4/3pr*3dn/dt)
Linear burning rate
95-80mass%; The gas temperature in bubble may be lower than 80 mass% aq. solution, as the two-phase region is relatively short. The nucleation and apparent burning rates become lower.
1000mm/s
1mm/s
80-50mass%；The gas temperature in bubbles may be lower than 80 mass% aq. solution because of higher water content. The nucleation and burning rates become lower. 18 18

19. Combustion mode in Zone3
Surface propagation rate increases rapidly by the local disturbance
(2) Local disturbance
Stable combustion
wave
(3) Concentration of reactive gas into concave area
(4) Expansion into liquid phase
(5) Expansion stops 19

20. Comparison of combustion wave structure
The jump mechanism of burning rate to high rate region is not clarified
Comparison of combustion wave structure
High rb
Zone3
Zone2
Zone1
Control
SHP069
SHP163
Combustion wave structures of propellant solutions are similar to aqueous solution in each burning rate zone
Low rb
Aqueous solution
Propellant solution 20 20

21. Phenomena of Burning Rate Jumping
Transition Process
Liquid
(4) New bubbles develop quickly
(5) Extremely high burning rate is established
New Bubble
(1) Stable combustion wave propagates
(3) New fine bubble are generated
(2) Brown bubble invade into liquid phase
Hydrodynamic instability is the trigger to jump to extremely high burning rate region 21

22. Hydrodynamic instability - 1
◆Margolis model; extended model of Landau/Levich instability
Stable at high pressure,
and at low methanol content
Our results;
Unstable at high pressure
Estimation result is opposite tendencies to our results
◆ Flame stretch effect
Lewis number effect; out of consideration
(Lewis number; no pressure dependency)
Markstein number（Ma）
Markstein number (by asymptotics)
Su(s); Burnign rate of stretched flame
Su(l); Laminar burning rate
Ka; Flame stretch ratio
By Clavin P., Energy Combust. Sci., vol.11, pp.1-59, 1985 22 22

23. Hydrodynamic instability - 3
Control
SHP069
SHP163
Unstable at high pressure,
and at low methanol content
Our results;
Unstable at high pressure
Hydrodynamic instability of propellant solutions is affected by flame stretch and determines the jump pressure.
Estimation results supports our results
Ma=Ma,cr
3.3MPa
5.0MPa
6.6MPa 23

24. Application to thruster
Objective
Development of HAN-based Monopropellant Thruster
Propellant; SHP163
Catalyst; S405
Propellant
Catalyst
Burning process
Monopropellant is injected into the preheated catalyst bed.
Chemical reaction of monopropellant occurs at the catalyst bed.
Gas products burn thoroughly in the combustor.
Combustion product gas is exhausted through the nozzle.
Heater

25. Free fall test 1/2 Objective Pretest of supersonic vehicle test flight
HAN-based thruster system
Launch
Y=0 sec
Y+20 sec
Start
Ｙ+50 sec
Finish
Thrusters burn
for 30 seconds
Sequence
Objective
Pretest of supersonic vehicle test flight
Balloon operation
Attitude control by N2 gas jets
HAN thrusters help the acceleration at free fall
Supersonic vehicle mock-up

26. Free fall test 2/2 Flight system Thruster
Diameter; 75 mm Length; mm
Nozzle
Thruster
Valve
Propellant Tank
Pressure sensor
Thermocouple
Combustion chamber
Injector
Catalyst bed

27. Static firing test
Simulated environmental test (Vacuum and Low temperature)
Thruster burned stably for 30 seconds in simulated condition

28. Static firing test (movie)

29. Result of free fall test
Specific impulse; 230 sec
Combustion efficiency; 0.88
　Thruster burned well for 30 seconds in the flight
　Density*Isp is approximately 1.46 times higher than the hydrazine
　This results show the potential for the application to space programs

30. Summary -Combustion mechanism-
Bubble nucleation rate by superheat governs the apparent linear burning rate in very high burning rate zone.
The water content dominates the burning rate zone in the case of aqueous solutions.
The hydrodynamic instability determines the burning rate zone in the case of propellant solutions. 30

31. Summary -Application to thruster-
Flight system is developed and burnt for 30 seconds successfully in vacuum and -50 C
Isp is approximately 230 seconds
The high potential of HAN-based thruster for the application to space programs was shown 31