5.5.4
Ek spacecraft thruster ko ek aisi liquid chahiye jo bahut saari chemical energy store kare, aur jab use ek hot catalyst ke upar push kiya jaye, toh instantly hot gas mein toot jaaye jo ek nozzle se bahar shoot ho. 60 saalon tak woh liquid hydrazine (N 2 H 4 carcinogenic, acutely toxic liquid jo ground crews ko bulky "SCAPE" hazmat suits pehenne par majboor karta tha.
Green propellants performance toh rakhte hain lekin toxic fuel ki jagah ek ionic liquid use karte hain jo safe-ish salts par based hoti hai. Trick yeh hai: ek energetic oxidiser salt (jaise ammonium dinitramide ya hydroxylammonium nitrate) aur ek fuel ko paani mein dissolve karo — tumhe ek dense, stable liquid milti hai jo far less toxic hai lekin actually hydrazine se zyada energy per litre pack karti hai.
Definition Teen propellants
Hydrazine — monopropellant N 2 H 4 LMP-103S (Sweden, ECAPS) — ek ADN -based blend: ~63% ammonium dinitramide (N H 4 N ( N O 2 ) 2 PRISMA (2010) par fly kiya gaya.AF-M315E / ASCENT (USA, AFRL) — ek HAN -based blend: ~44% hydroxylammonium nitrate (N H 3 O H + N O 3 − GPIM (2019) par fly kiya gaya.
Intuition "Ionic liquid" kyun?Ek ionic liquid ek salt hota hai jo liquid rehta hai kyunki hum use ek concentrated aqueous solution / low-melting mix ke roop mein rakhte hain. Ions non-volatile hote hain → almost koi toxic vapour cloud nahi → yahi poora safety win hai. Hydrazine ka khatre bada hissa uski high vapour pressure hai; ADN aur HAN salts muskil se evaporate hoti hain.
Intuition Teen numbers jo matter karte hain
Specific impulse I s p — fuel efficiency (s). Zyada = zyada Δ v Density ρ — kg/L. Zyada = ek fixed tank mein zyada fuel.Toxicity / handling cost — green ones ko fuel karna sasta hai.
Greens density-impulse (ρ I s p easy cold-start mein jeet jaata hai (low catalyst light-off temperature).
Property
Hydrazine
LMP-103S
AF-M315E
Base salt
— (N 2 H 4
ADN
HAN
I s p ~230
~252
~266
Density (kg/L)
~1.01
~1.24
~1.47
ρ I s p low
high
highest
Toxicity
severe
low
low
Catalyst preheat
low
high
very high
Intuition Thrust kyun exist karta haiThrust sirf momentum conservation hai: mass ko peeche phenko, rocket aage jaata hai. "Fuel quality" ka sawaal ban jaata hai: chemistry exhaust ko kitni tezi se peeche phek sakti hai?
Intuition Toh AF-M315E hydrazine se better kyun hai?HAN combustion zyada garam chalti hai (higher T c N 2 , H 2 , N H 3 halka hai (low M T c
Worked example Example 1 —I s p I s p ≈ 266 v e v e = I s p g 0 = 266 × 9.81 = 2609 m/s Yeh step kyun? I s p = v e / g 0
Worked example Example 2 — Density-impulse: tank metricAF-M315E (ρ = 1.47 I s p = 266 ρ = 1.01 I s p = 230 ρ I s p = 1.47 × 266 = 391 = 1.01 × 230 = 232 = 391/232 = 1.69 Yeh step kyun? Ek fixed-volume tank ρ V I s p g 0 ∝ ρ I s p same tank se ~69% zyada impulse deliver karta hai — chhote satellites ke liye bahut bada.
Worked example Example 3 — Zyada garam kyun help karta hai (theT c / M T c = 1900 M = 22 T c = 900 M = 11 T c / M = 1900/22 = 9.30 = 900/11 = 9.05 Yeh step kyun? Bhale hi green ka exhaust do guna bhaari hai, uska temperature do gune se bhi zyada high hai, toh ratio phir bhi jeet jaata hai. Yeh dikhata hai T c M
Worked example Example 4 — Rocket equation seΔ v v e = 2609 Δ v = v e ln m f m 0 = 2609 ln 90 100 = 2609 × 0.1054 = 275 m/s Yeh step kyun? Tsiolkovsky's Δ v = v e ln ( m 0 / m f )
Common mistake "Green propellant = non-toxic, bilkul safe."Kyun sahi lagta hai: marketing word "green" + low vapour hazard.
Fix: Yeh low-toxicity aur low-vapour hain, inert NAHI. ADN/HAN energetic oxidisers hain — yeh deflagrate kar sakte hain, aur HAN corrosive hai. "Green" yahan matlab hai reduced handling hazard & environmental load , naki harmless.
Common mistake "Zyada density matlab bhaari rocket — bura hai."Kyun sahi lagta hai: rozmarra ki zindagi mein bhaari = bura.
Fix: Ek fixed tank volume ke liye, zyada density matlab zyada propellant mass = zyada total impulse (ρ I s p
Common mistake "Greens har jagah jeette hain, toh hydrazine obsolete hai."Kyun sahi lagta hai: higher I s p Fix: Greens ko bahut zyada hot catalyst preheat chahiye (high light-off temperature) → zyada electrical power aur slow cold starts. Hydrazine ka easy, instant cold-start use kuch missions ke liye relevant rakhta hai.
I s p g 0 Fix: I s p seconds mein ⇒ v e g 0 = 9.81
Recall Feynman: 12-saal ke bachche ko samjhaoEk rocket gas ko peeche thokte hue aage badhta hai — jaise ek phuli hui balloon ko chod do. Purana "fuel" uss thoke ke liye hydrazine tha, jo bahut achha kaam karta hai lekin zahar hai — workers sirf use daalne ke liye spacesuit pehnte hain. Scientists ne naaye "namkeen paani" waale fuels dhundhe (LMP-103S, AF-M315E) jo handle karne mein bahut safe hain, zahrile clouds nahi banaate, aur actually thoda zyada gas thokte hain aur same bottle mein zyada fuel fit karte hain. Ek hi pareshani: yeh shuru hone se pehle engine ko zyada warm up karna padta hai. Toh: same kaam, bahut safer, warm-up power par thoda zyada bhookha.
Mnemonic Salts aur rule yaad rakho"AF has HAN, LMP has ADN." (Dono -AN/-DN par khatam hote hain, dono = nitrogen-rich oxidiser salts.)
Performance rule: "Hot & Heavy beats Cool & Light" → I s p ∝ T c / M T c
LMP-103S ki base mein kaunsi ionic salt hai? Ammonium dinitramide (ADN), N H 4 N ( N O 2 ) 2
AF-M315E (ASCENT) ki base mein kaunsi salt hai? Hydroxylammonium nitrate (HAN), N H 3 O H + N O 3 −
Hydrazine ka chemical formula? N 2 H 4
Specific impulse define karo aur uska formula batao. Thrust per weight-flow of propellant, I s p = F / ( m ˙ g 0 ) = v e / g 0
I s p I s p ∝ T c / M — hot flame ke saath upar, bhaari exhaust ke saath neeche
Green propellants "green" kyun hain? Non-volatile ionic salts → almost koi toxic vapour nahi; products hain N 2 , H 2 O , C O 2
"Fixed tank se impulse" kaun sa metric capture karta hai aur kaun jeetta hai? Density-impulse ρ I s p
Ek area jahan hydrazine abhi bhi greens ko peechhe chhodta hai? Low catalyst light-off / preheat temperature → easy, instant cold start
I s p = 266 v e v e = 266 × 9.81 ≈ 2609
Pehle kaun sa mission AF-M315E / LMP-103S fly kiya? GPIM (2019) ne AF-M315E fly kiya; PRISMA (2010) ne LMP-103S fly kiya
Hydrazine ki main decomposition reaction? 3 N 2 H 4 → 4 N H 3 + N 2
Rocket equation batao. Δ v = v e ln ( m 0 / m f )
Green Chemistry & Sustainability — atom economy & safer reagents principle aerospace par apply hota haiIonic liquids — enabling concept ke roop mein non-volatile saltsHydrazine — legacy monopropellant & uski toxicityCatalysis — Shell 405 (Ir/Al₂O₃) vs high-temperature green-propellant catalystsRocket equation (Tsiolkovsky) — I s p Δ v Thermochemistry & enthalpy of decomposition — flame temperature T c Oxidisers — nitrate & dinitramide chemistry — internal oxygen source
Toxic carcinogenic vapour
Density-impulse rho x Isp
Specific impulse Isp = ve/g0
