Rocket fuel: varieties and composition. Solid rocket motors

"...And there is nothing new under the sun"

(Ecclesiastes 1:9).
About fuels, rockets, rocket engines has been written, is being written, and will continue to be written.

One of the first works on liquid rocket engine fuels can be considered the book by V.P. Glushko" Liquid fuel For jet engines", published in 1936.

For me, the topic seemed interesting, related to my former specialty and studies at the university, especially since my youngest son “dragged” it: “Chief, let’s knead what the thread is and run it, and if you’re lazy, then we ourselves"Let's figure it out." Apparently they don't give me peace.

I really want to blow up my rocket engine properly.

We will “think” together, under strict parental control. Hands and legs must be intact, especially strangers.

An important parameter is the oxidizer excess coefficient (denoted by the Greek “α” with the subscript “ok.”) and the mass ratio of the components Km.

Km=(dmok./dt)/(dmg../dt), i.e. the ratio of the mass flow rate of the oxidizer to the mass flow rate of the fuel. It is specific for each fuel. Ideally, it is a stoichiometric ratio of oxidizer and fuel, i.e. shows how many kg of oxidizer is needed to oxidize 1 kg of fuel. However real values differ from ideal. The ratio of real Km to ideal is the oxidizer excess coefficient.

As a rule, α is approx.<=1. И вот почему. Зависимости Tk(αок.) и Iуд.(αок.) нелинейны и для многих топлив последняя имеет максимум при αок. не при стехиометрическом соотношении компонентов, т.е макс. значения Iуд. получаются при некотором снижении количества окислителя по отношению к стехиометрическому. Ещё немного терпения, т.к. не могу обойти понятие: . Это пригодится и в статье, и в повседневной жизни.

In short, enthalpy is energy. Two aspects of this article are important:
Thermodynamic enthalpy- the amount of energy spent on the formation of a substance from the initial chemical elements. For substances consisting of identical molecules (H 2, O 2, etc.), it is equal to zero.
Enthalpy of combustion- makes sense only if a chemical reaction occurs. In reference books you can find values ​​of this quantity experimentally obtained under normal conditions. Most often, for combustibles this is complete oxidation in an oxygen environment, for oxidizers it is the oxidation of hydrogen with a given oxidizer. Moreover, the values ​​can be both positive and negative depending on the type of reaction.

“The sum of the thermodynamic enthalpy and the enthalpy of combustion is called the total enthalpy of the substance. Actually, this value is used in the thermal calculation of liquid-propellant rocket engine chambers.”

Requirements for ZhRT:
-as a source of energy;
-as a substance that has to be used (at this level of technology development) for cooling the rocket engines and pumping pumps, sometimes for pressurizing tanks with rocket engines, providing it with volume (stage rocket tanks), etc.;
-as to a substance outside the rocket engine, i.e. during storage, transportation, refueling, testing, environmental safety, etc.

This gradation is relatively arbitrary, but in principle it reflects the essence. I will name these requirements as follows: No. 1, No. 2, No. 3. Someone can add to the list in the comments.
These requirements are a classic example that “pull” the creators of RD in different directions:

# From the point of view of the LRE energy source (No. 1)

Those. you need to get max. Iud. I won’t bother everyone further, in general:

With other important parameters for No. 1, we are interested in R and T (with all indices).
Need to: the molecular weight of combustion products was minimal, and the specific heat content was maximum.

# From the point of view of the launch vehicle designer (No. 2):

TCs must have maximum density, especially in the first stages of rockets, because they are the most voluminous and have the most powerful thrusters, with a high per second flow rate. Obviously, this is not consistent with requirement No. 1.

# From operational tasks important (No. 3):

Chemical stability of TC;
- ease of refueling, storage, transportation and manufacturing;
- environmental safety (in the entire “field” of application), namely toxicity, cost of production and transportation, etc. and safety during RD operation (explosion hazard).

For more details, see "The saga of rocket fuels - the other side of the coin."

I hope no one has fallen asleep yet? I feel like I'm talking to myself. Coming soon about alcohol, stay tuned!

Of course, this is just the tip of the iceberg. There are also additional requirements here, due to which one should look for CONSENSUSES and COMPROMISES. One of the components must have satisfactory (preferably excellent) coolant properties, because at this level of technology it is necessary to cool the combustor and the nozzle, as well as protect the critical section of the taxiway:

The photograph shows the nozzle of the XLR-99 liquid-propellant rocket engine: a characteristic design feature of the American liquid-propellant rocket engines of the 50-60s is clearly visible - a tubular chamber:

It is also required (as a rule) to use one of the components as a working fluid for the turbocharger turbine:

For fuel components, “saturated vapor pressure is of great importance (roughly speaking, the pressure at which a liquid begins to boil at a given temperature). This parameter greatly influences the design of pumps and the weight of tanks.”/ S.S. Fakas/

An important factor is the aggressiveness of the TC towards the materials (CM) of the liquid propellant rocket engine and the tanks for their storage.
If fuel oils are very “harmful” (as some people are), then engineers have to spend money on a number of special measures to protect their structures from fuel.

Classification of liquid gas is most often based on saturated vapor pressure or, more simply put, boiling point at normal pressure.

High-boiling components of liquid fuel.

Such liquid rocket engines can be classified as multi-fuel.
A liquid-propellant rocket engine using three-component fuel (fluorine+hydrogen+lithium) was developed in.

Binary fuels consist of an oxidizer and a fuel.
Liquid propellant engine Bristol Siddeley BSSt.1 Stentor: two-component liquid propellant engine (H2O2 + kerosene)

Oxidizing agents

Oxygen

Chemical formula-O 2 (dioxygen, American designation Oxygen-OX).
Liquid propellant engines use liquid oxygen rather than gaseous oxygen - Liquid oxygen (LOX - briefly and everything is clear).
Molecular weight (for a molecule) is 32 g/mol. For lovers of precision: atomic mass (molar mass) = 15.99903;
Density=1.141 g/cm³
Boiling point=90.188K (−182.96°C)

From a chemical point of view, it is an ideal oxidizing agent. It was used in the FAA's first ballistic missiles and its American and Soviet counterparts. But its boiling point did not suit the military. The required operating temperature range is from –55°C to +55°C (long preparation time for launch, short time on combat duty).

Very low corrosiveness. Production has been mastered for a long time, the cost is low: less than $0.1 (in my opinion, several times cheaper than a liter of milk).
Flaws:

Cryogenic - cooling and constant refueling are required to compensate for losses before launch. It can also spoil other TCs (kerosene):

In the photo: the doors of the protective devices of the kerosene refueling automatic docking station (ZU-2), 2 minutes before the end of the cyclogram when performing the operation CLOSE CHECKER did not close completely due to icing. At the same time, due to icing, the signal about the TUA leaving the launcher did not go through. The launch took place the next day.

The RB liquid oxygen filling unit was removed from the wheels and installed on the foundation.

It is difficult to use the CS and liquid rocket engine nozzle as a coolant.

"ANALYSIS OF THE EFFICIENCY OF USE OF OXYGEN AS A COOLER FOR A LIQUID ROCKET ENGINE CHAMBER" SAMOSHKIN V.M., VASYANINA P.YU., Siberian State Aerospace University named after Academician M.F. Reshetnyova

Now everyone is studying the possibility of using supercooled oxygen or oxygen in a sludge-like state, in the form of a mixture of solid and liquid phases of this component. The view will be approximately the same as this beautiful ice slush in the bay to the right of Shamora:

Imagine: instead of H 2 O, imagine LCD (LOX).

Sugaring will increase the overall density of the oxidizer.

An example of cooling (supercooling) of the R-9A ballistic missile: for the first time, it was decided to use supercooled liquid oxygen as an oxidizer in a rocket, which made it possible to reduce the total time to prepare the rocket for launch and increase the degree of its combat readiness.

Note: For some reason, the famous writer Dmitry Konanykhin bent over (almost “chocked”) Elon Musk for this same procedure.
Cm:

Ozone-O 3

Molecular mass=48 amu, molar mass=47.998 g/mol
The density of the liquid at -188 °C (85.2 K) is 1.59 (7) g/cm³
The density of solid ozone at −195.7 °C (77.4 K) is 1.73(2) g/cm³
Melting point −197.2(2) °C (75.9 K)

Engineers have long struggled with it, trying to use it as a high-energy and at the same time environmentally friendly oxidizer in rocket technology.

The total chemical energy released during the combustion reaction involving ozone is approximately one quarter greater than for simple oxygen (719 kcal/kg). Accordingly, Iud will be greater. Liquid ozone has a higher density than liquid oxygen (1.35 versus 1.14 g/cm³, respectively), and its boiling point is higher (−112 °C and −183 °C, respectively).

So far, an insurmountable obstacle is the chemical instability and explosiveness of liquid ozone with its decomposition into O and O2, in which a detonation wave appears moving at a speed of about 2 km/s and a destructive detonation pressure of more than 3 107 dyne/cm2 (3 MPa) develops, which makes the use of liquid ozone is impossible with the current level of technology, with the exception of the use of stable oxygen-ozone mixtures (up to 24% ozone). The advantage of such a mixture is also a higher specific impulse for hydrogen engines compared to ozone-hydrogen engines. Today, such highly efficient engines as RD-170, RD-180, RD-191, as well as accelerating vacuum engines, have reached Isp parameters close to the maximum values, and to increase the efficiency there is only one option left, related to the transition to new types of fuel .

Nitric acid-HNO3

Condition - liquid at no.
Molar mass 63.012 g/mol (doesn't matter what I use or molecular mass - it doesn't change the point)
Density=1.513 g/cm³
T. melt.=-41.59 °C, T. boil.=82.6 °C

HNO3 has a high density, low cost, is produced in large quantities, is quite stable, including at high temperatures, and is fire and explosion-proof. Its main advantage over liquid oxygen is its high boiling point, and, therefore, the ability to be stored indefinitely without any thermal insulation. The nitric acid molecule HNO 3 is an almost ideal oxidizing agent. It contains a nitrogen atom and a “half” water molecule as “ballast”, and two and a half oxygen atoms can be used to oxidize the fuel. But it was not there! Nitric acid is such an aggressive substance that it continuously reacts with itself—hydrogen atoms are split off from one acid molecule and join neighboring ones, forming fragile but extremely chemically active aggregates. Even the most resistant grades of stainless steel are slowly destroyed by concentrated nitric acid (as a result, a thick greenish “jelly”, a mixture of metal salts, is formed at the bottom of the tank). To reduce the corrosiveness, various substances began to be added to nitric acid; just 0.5% hydrofluoric acid reduces the corrosion rate of stainless steel tenfold.

To increase the shock pulse, nitrogen dioxide (NO 2) is added to the acid. The addition of nitrogen dioxide to the acid binds the water entering the oxidizer, which reduces the corrosive activity of the acid, increases the density of the solution, reaching a maximum at 14% dissolved NO 2. The Americans used this concentration for their military missiles.

We have been looking for suitable containers for nitric acid for almost 20 years. It is very difficult to select construction materials for tanks, pipes, and combustion chambers of liquid propellant rocket engines.

The oxidizer option that was chosen in the USA is with 14% nitrogen dioxide. But our rocket scientists acted differently. It was necessary to catch up with the United States at any cost, so Soviet brand oxidizers - AK-20 and AK-27 - contained 20 and 27% tetroxide.

Interesting fact: In the first Soviet rocket fighter BI-1, nitric acid and kerosene were used for flight.

Tanks and pipes had to be made of Monel metal: an alloy of nickel and copper, it became a very popular structural material among rocket scientists. Soviet rubles were almost 95% made from this alloy.

Disadvantages: tolerable "muck". Corrosive active. The specific impulse is not high enough. Currently, it is almost never used in its pure form.

Nitrogen tetroxide-AT (N 2 O 4)

Molar mass=92.011 g/mol
Density=1.443 g/cm³

"Took up the baton" from nitric acid in military engines. It is self-flammable with hydrazine and UDMH. Low boiling point, but can be stored for a long time if special care is taken.

Disadvantages: the same nasty thing as HNO 3, but with its own quirks. May decompose into nitric oxide. Toxic. Low specific impulse. The oxidizing agent AK-NN was and is often used. It is a mixture of nitric acid and nitric tetroxide, sometimes called "red fuming nitric acid." The numbers indicate the percentage of N 2 O 4.

These oxidizers are mainly used in military rocket engines and spacecraft rocket engines due to their properties: durability and self-ignition. Typical fuels for AT are UDMH and hydrazine.

Fluorine-F 2

Atomic mass = 18.998403163 a. e.m. (g/mol)
Molar mass of F2, 37.997 g/mol
Melting point=53.53 K (−219.70 °C)
Boiling point = 85.03 K (−188.12 °C)
Density (for liquid phase), ρ=1.5127 g/cm³

Fluorine chemistry began to develop in the 1930s, especially quickly during the Second World War of 1939-45 and after it in connection with the needs of the nuclear industry and rocket technology. The name "Fluorine" (from the Greek phthoros - destruction, death), proposed by A. Ampere in 1810, is used only in Russian; in many countries the name is accepted "fluor". It is an excellent oxidizing agent from a chemical point of view. It oxidizes oxygen, water, and practically everything. Calculations show that the maximum theoretical Isp can be obtained on the F2-Be (beryllium) pair - about 6000 m/s!

Super? Bummer, not "super"...

You wouldn't wish such an oxidizer on your enemy.
Extremely corrosive, toxic, prone to explosions upon contact with oxidizing materials. Cryogenic. Any combustion product also has almost the same “sins”: they are terribly corrosive and toxic.

Safety precautions. Fluorine is toxic, its maximum permissible concentration in the air is approximately 2·10-4 mg/l, and the maximum permissible concentration with exposure for no more than 1 hour is 1.5·10-3 mg/l.

The 8D21 liquid-propellant rocket engine using the fluorine + ammonia pair gave a specific impulse at the level of 4000 m/s.
For the pair F 2 +H 2 it turns out Isp = 4020 m/s!
Trouble: HF hydrogen fluoride in the exhaust.

Starting position after launching such an “energetic engine”?
A puddle of liquid metals and other chemical and organic objects dissolved in hydrofluoric acid!
H 2 +2F=2HF, at room temperature exists in the form of a dimer H 2 F 2.

Mixes with water in any ratio to form hydrofluoric acid. And its use in rocket engines of spacecraft is not realistic due to the deadly complexity of storage and the destructive effect of combustion products.

The same applies to other liquid halogens, for example, chlorine.

A hydrogen fluorine liquid-propellant rocket engine with a thrust of 25 tons to equip both stages of the rocket accelerator was supposed to be developed in V.P. Glushko based on a spent liquid-propellant rocket engine with a thrust of 10 tons using fluoroammonia (F 2 + NH 3) fuel.

Hydrogen peroxide-H 2 O 2 .

I mentioned it above in single-component fuels.

Walter HWK 109-507: advantages in the simplicity of the rocket engine design. A striking example of such a fuel is hydrogen peroxide.

Alles: the list of more or less real oxidizing agents is complete. I focus on HCl O 4. As independent oxidizing agents based on perchloric acid, the only ones of interest are: monohydrate (H 2 O + ClO 4) - a solid crystalline substance and dihydrate (2HO + HClO 4) - a dense viscous liquid. Perchloric acid (which, due to Isp, in itself is unpromising), is of interest as an additive to oxidizers, guaranteeing the reliability of self-ignition of the fuel.

Oxidizing agents can be classified as follows:

The final (most often used) list of oxidizers in conjunction with real combustibles:

Note: if you want to convert one specific impulse option to another, you can use a simple formula: 1 m/s = 9.81 s.

Unlike them, we have flammable ones.

Flammable

Main characteristics of two-component liquid propellants at pк/pa=7/0.1 MPa

Based on their physical and chemical composition, they can be divided into several groups:

Hydrocarbon fuels.
Low molecular weight hydrocarbons.
Simple substances: atomic and molecular.

For this topic, so far only hydrogen (Hydrogenium) is of practical interest.
I will not consider Na, Mg, Al, Bi, He, Ar, N 2, Br 2, Si, Cl 2, I 2, etc. in this article.
Hydrazine fuels ("stinkers").

Wake up, sleepyheads - we have already reached alcohol (C2H5OH).

The search for the optimal fuel began with the development of liquid propellant rocket engines by enthusiasts. The first widely used fuel was ethanol), used in the first
Soviet missiles R-1, R-2, R-5 ("legacy" of the FAU-2) and on the Vergeltungswaffe-2 itself.

More precisely, a solution of 75% ethyl alcohol (ethanol, ethyl alcohol, methyl carbinol, wine alcohol or alcohol, often colloquially simply “alcohol”) - monohydric alcohol with the formula C 2 H 5 OH (empirical formula C 2 H 6 O), another option: CH 3 -CH 2 -OH
This fuel two serious shortcomings, which obviously did not suit the military: low energy performance and.

Proponents of a healthy lifestyle (alcohol phobes) tried to solve the second problem with the help of furfuryl alcohol. It is a poisonous, mobile, transparent, sometimes yellowish (to dark brown) liquid that turns red over time when exposed to air. BARBARIANS!

Chem. formula: C 4 H 3 OCH 2 OH, Rat. formula:C 5 H 6 O 2. Disgusting slurry. Not suitable for drinking.

Hydrocarbon group.

Kerosene

Conditional formula C 7.2107 H 13.2936
A flammable mixture of liquid hydrocarbons (from C 8 to C 15) with a boiling point in the range of 150-250 ° C, transparent, colorless (or slightly yellowish), slightly oily to the touch
density - from 0.78 to 0.85 g/cm³ (at a temperature of 20°C);
viscosity - from 1.2 – 4.5 mm²/s (at a temperature of 20°C);
flash point - from 28°C to 72°C;
calorific value - 43 MJ/kg.

My opinion: it is pointless to write about the exact molar mass

Kerosene is a mixture of various hydrocarbons, which is why scary fractions appear (in the chemical formula) and a “smeared” boiling point. Convenient high-boiling fuel. It has been used for a long time and successfully all over the world in engines and aviation. This is what Soyuz aircraft still fly on. Low toxicity (I strongly do not recommend drinking), stable. Still, kerosene is dangerous and harmful to health (oral consumption).
The Ministry of Health is categorically against it!
Soldier's tales: good for getting rid of nasty ones.

However, it also requires careful handling during operation:

Significant advantages: relatively inexpensive, mastered in production. The kerosene-oxygen pair is ideal for the first stage. Its specific impulse on the ground is 3283 m/s, void 3475 m/s. Flaws. Relatively low density.

American rocket kerosene Rocket Propellant-1 or Refined Petroleum-1

Relatively was.
To increase density, leaders in space exploration developed syntin (USSR) and RJ-5 (USA).
.

Kerosene has a tendency to deposit tarry deposits in the lines and cooling path, which negatively affects cooling. This bad quality of his is emphasized.
Kerosene engines were most developed in the USSR.

A masterpiece of human intelligence and engineering, our “pearl” RD-170/171:

Now the term “hydrocarbon fuel” has become a more correct name for kerosene-based fuels, because from kerosene, which was burned in safe kerosene lamps by I. Lukasiewicz and J. Zech, the used UVG “went away” very much.

In fact, Roscosmos gives out misinformation:

After fuel components are pumped into its tanks - naphthyl (rocket fuel)), liquefied oxygen and hydrogen peroxide, the space transport system will weigh more than 300 tons (depending on the modification of the launch vehicle.

Low molecular weight hydrocarbons

Methane-CH4

Molar mass: 16.04 g/mol
Density gas (0 °C) 0.7168 kg/m³;
liquid (−164.6 °C) 415 kg/m³
Melting temperature=-182.49 °C
Bp = -161.58 °C

It is now considered by everyone as a promising and cheap fuel, as an alternative to kerosene and hydrogen.
Chief designer Vladimir Chvanov:

The specific impulse of an LNG engine is high, but this advantage is offset by the fact that methane fuel has a lower density, so the total energy advantage is insignificant. From a design point of view, methane is attractive. To free the engine cavities, you only need to go through an evaporation cycle - that is, the engine is more easily freed from product residues. Due to this, methane fuel is more acceptable from the point of view of creating a reusable engine and a reusable aircraft.

Inexpensive, common, stable, low-toxic. Compared to hydrogen, it has a higher boiling point, and the specific impulse paired with oxygen is higher than that of kerosene: about 3250-3300 m/s on earth. Not a bad cooler.

Flaws. Low density (half that of kerosene). In some combustion modes, it can decompose with the release of carbon in the solid phase, which can lead to a drop in momentum due to the two-phase flow and a sharp deterioration in the cooling mode in the chamber due to soot deposition on the walls of the combustion chamber. Recently, active research and development activities have been carried out in the field of its use (along with propane and natural gas), even in the direction of modifying existing gas. LRE (in particular, such work was carried out on).

Roscosmos already in 2016 began developing a power plant using liquefied natural gas.

Or "Kinder Surpeis", as an example: American Raptor engine from Space X:

These fuels include propane and natural gas. Their main characteristics as combustibles are close (with the exception of higher density and higher boiling point) to hydrocarbons. And there are the same problems when using them.

-H 2 (Liquid: LH 2) stands out among flammables.

The molar mass of hydrogen is 2016 g/mol or approximately 2 g/mol.
Density (at no.)=0.0000899 (at 273 K (0 °C)) g/cm³
Melting point=14.01K (-259.14 °C);
Boiling point=20.28K (-252.87 °C);

The use of the LOX-LH 2 pair was proposed by Tsiolkovsky, but implemented by others:

From the point of view of thermodynamics, H 2 is an ideal working fluid for both the liquid propellant engine itself and the TNA turbine. An excellent coolant, both in liquid and gaseous states. The latter fact makes it possible not to be particularly afraid of the boiling of hydrogen in the cooling path and to use hydrogen gasified in this way to drive the pump.

This scheme is implemented in the Aerojet Rocketdyne RL-10 - simply a gorgeous (from an engineering point of view) engine:

Our analogue ( even better, because younger): RD-0146 (D, DM) - a gas-free liquid-propellant rocket engine developed by the Chemical Automatics Design Bureau in Voronezh.

Particularly effective with a nozzle made of Grauris material. But it doesn't fly yet

This TC provides a high specific impulse - when paired with oxygen, 3835 m/s.

This is the highest figure among those actually used. These factors determine the keen interest in this fuel. Environmentally friendly, at the “output” in contact with O 2: water (water vapor). Common, virtually unlimited supplies. Mastered in production. Non-toxic. However, there are a lot of fly in the ointment in this barrel of honey.

1. Extremely low density. Everyone has seen the huge hydrogen tanks of the Energia launch vehicle and the Space Shuttle. Due to the low density, it is applicable (as a rule) at the upper stages of the launch vehicle.

In addition, low density poses a difficult challenge for pumps: hydrogen pumps are multistage in order to provide the required mass flow without cavitating.

For the same reason it is necessary to install the so-called fuel booster pumping units (FPU) immediately behind the intake device in the tanks, in order to make life easier for the main fuel pump.

Hydrogen pumps also require a significantly higher rotation speed of the pump for optimal operation.

2. Low temperature. Cryogenic fuel. Before refueling, it is necessary to cool (and/or supercool) the tanks and the entire tract for many hours. LV tanks "Falocn 9FT" - a look from the inside:

More about "surprises":
"MATHEMATICAL MODELING OF HEAT AND MASS TRANSFER PROCESSES IN HYDROGEN SYSTEMS" N0R V.A. Gordeev V.P. Firsov, A.P. Gnevashev, E.I. Postoyuk
FSUE "GKNPTs im. M.V. Khrunichev, KB "Salyut"; "Moscow Aviation Institute (State Technical University)

The paper describes the main mathematical models of heat and mass transfer processes in the tank and hydrogen lines of the oxygen-hydrogen upper stage 12KRB. Anomalies in the supply of hydrogen to the liquid-propellant rocket engine were identified and their mathematical description was proposed. The models were tested during bench and flight tests, which made it possible to use them to predict the parameters of serial upper stages of various modifications and make the necessary technical decisions to improve pneumohydraulic systems.

The low boiling point makes it difficult to pump into tanks and store this fuel in tanks and storage facilities.

3. Liquid hydrogen has some properties of a gas:

Compressibility coefficient (pv/RT) at 273.15 K: 1.0006 (0.1013 MPa), 1.0124 (2.0266 MPa), 1.0644 (10.133 MPa), 1.134 (20.266 MPa), 1.277 (40.532 MPa);
Hydrogen can be in ortho and para states. Orthohydrogen (o-H2) has a parallel (same sign) orientation of nuclear spins. Para-hydrogen (p-H2)-antiparallel.

At normal and high temperatures, H2 (normal hydrogen, n-H2) is a mixture of 75% ortho and 25% para modifications, which can mutually convert into each other (ortho-para transformation). When o-H 2 is converted to p-H 2, heat is released (1418 J/mol).

All this imposes additional difficulties in the design of pipelines, liquid propellant engines, pumping pumps, operating schedules, and especially pumps.

4. Hydrogen gas spreads faster than other gases in space, passes through small pores, and at high temperatures penetrates steel and other materials relatively easily. H 2g has high thermal conductivity, equal to 0.1717 W/(m*K) at 273.15 K and 1013 hPa (7.3 relative to air).

Hydrogen in its normal state at low temperatures is inactive; without heating it reacts only with F 2 and in the light with Cl 2. Hydrogen reacts more actively with nonmetals than with metals. Reacts with oxygen almost irreversibly, forming water with the release of 285.75 MJ/mol of heat;

5. Hydrogen forms hydrides with alkali and alkaline earth metals, elements of groups III, IV, V and VI of the periodic system, as well as with intermetallic compounds. Hydrogen reduces the oxides and halides of many metals to metals, and unsaturated hydrocarbons to saturated ones (see).
Hydrogen gives up its electron very easily. In solution, it is detached in the form of a proton from many compounds, causing their acidic properties. In aqueous solutions, H+ forms a hydronium ion H 3 O with a water molecule. Being part of the molecules of various compounds, hydrogen tends to form a hydrogen bond with many electronegative elements (F, O, N, C, B, Cl, S, P).

6. Fire and explosion hazard. There is no need to pickle it: everyone knows the explosive mixture.
A mixture of hydrogen and air explodes from the slightest spark in any concentration - from 5 to 95 percent.

Is the Space Shuttle Main Engine (SSME) impressive?

Now estimate its cost!
Probably, having seen this and calculating the costs (the cost of putting 1 kg of payload into orbit), legislators and those who rule the budget of the United States and NASA in particular... decided “well, screw it.”
And I understand them - the Soyuz launch vehicle is both cheaper and safer, and the use of the RD-180/181 eliminates many of the problems of American launch vehicles and significantly saves taxpayers’ money in the richest country in the world.

The best rocket engine is one that you can make/buy that will have the thrust you want (not too much or too little) and will be as efficient (specific impulse, combustion chamber pressure) as its price will not become too heavy for you. /Philip Terekhov@lozga

Hydrogen engines are the most developed in the USA.
Now we are positioned in 3-4 place in the “Hydrogen Club” (after Europe, Japan and China/India).

I will separately mention solid and metallic hydrogen.

Solid hydrogen crystallizes in a hexagonal lattice (a = 0.378 nm, c = 0.6167 nm), at the nodes of which there are H 2 molecules connected to each other by weak intermolecular forces; density 86.67 kg/m³; С° 4.618 J/(mol*K) at 13 K; dielectric. At pressures above 10,000 MPa, a phase transition is expected with the formation of a structure built from atoms and possessing metallic properties. The possibility of “metallic hydrogen” superconductivity has been theoretically predicted.

Solid hydrogen is the solid state of aggregation of hydrogen.
Melting point −259.2 °C (14.16 K).
Density 0.08667 g/cm³ (at −262 °C).
White snow-like mass, crystals of hexagonal system.

The Scottish chemist J. Dewar in 1899 was the first to obtain hydrogen in the solid state. To do this, he used a regenerative cooling machine based on the .

The trouble is with him. He constantly gets lost: . This is understandable: a cube of molecules is obtained: 6x6x6. Just “giant” volumes - just “refuel” the rocket right now. For some reason this reminded me. This nano-miracle has not been found for 7 years or more.

I’ll leave anameson, antimatter, and metastable helium behind the scenes for now.

...
Hydrazine fuels ("stinkers")
Hydrazine-N2H4

State at zero - colorless liquid
Molar mass=32.05 g/mol
Density=1.01 g/cm³

A very common fuel.
It keeps for a long time, and they “love it” for it. Widely used in spacecraft control systems and ICBMs/SLBMs, where durability is critical.

For those who are confused by Iud in the dimension N*s/kg, I answer: this designation is “loved” by the military.
Newton is a derived unit, based on which it is defined as a force that changes the speed of a body weighing 1 kg by 1 m/s in 1 second in the direction of the force. Thus, 1 N = 1 kg m/s 2.
Accordingly: 1 N*s/kg =1 kg m/s 2 *s/kg=m/s.
Mastered in production.

Disadvantages: toxic, smelly.

The toxicity of hydrazine to humans has not been determined. According to calculations by S. Krop, a dangerous concentration should be considered 0.4 mg/l. Ch. Comstock and co-workers believe that the maximum permissible concentration should not exceed 0.006 mg/l. According to more recent American data, this concentration at 8-hour exposure is reduced to 0.0013 mg/l. It is important to note that the threshold for the olfactory sensation of hydrazine in humans significantly exceeds the indicated numbers and is equal to 0.014-0.030 mg/l. Significant in this regard is the fact that the characteristic odor of a number of hydrazine derivatives is felt only in the first minutes of contact with them. Subsequently, due to the adaptation of the olfactory organs, this sensation disappears, and a person, without noticing it, can remain for a long time in a contaminated atmosphere containing toxic concentrations of the said substance.

Hydrazine vapors explode under adiabatic compression. It is prone to decomposition, which, however, allows it to be used as a monopropellant for low-thrust liquid rocket engines (LPRE). Due to the development of production, it is more common in the USA.

Unsymmetrical dimethylhydrazine (UDMH)-H 2 N-N(CH 3) 2

Chem. formula: C2H8N2, Rat. formula:(CH3)2NNH2
State at zero - liquid
Molar mass=60.1 g/mol
Density=0.79±0.01 g/cm³

Widely used on military engines due to its durability. When mastering ampullation technology, all problems practically disappeared (except for disposal and accidents with allowances).

Has higher impulse compared to hydrazine.

Density and specific impulse with basic oxidizers are lower than kerosene with the same oxidizers. Will spontaneously ignite with nitrogen oxidizers. Mastered in production in the USSR.
More common in the USSR.
And in the jet engine of a French fighter-bomber (good video, I recommend) UDMH is used as an activating additive to traditional fuel.

Regarding hydrazine fuels.

Specific thrust is equal to the ratio of thrust to weight fuel consumption; in this case it is measured in seconds (s = N s/N = kgf s/kgf). To convert weight specific thrust into mass thrust, it must be multiplied by the acceleration of gravity (approximately equal to 9.81 m/s²)

Left behind the scenes:
Aniline, methyl-, dimethyl- and trimethylamines and CH 3 NHNH 2 -Methylhydrazine (aka monomethylhydrazine or heptyl), etc.

They are not that common. The main advantage of flammable hydrazine group is its long shelf life when using high-boiling oxidizers. Working with them is very unpleasant - toxic flammable, aggressive oxidizing agents, toxic combustion products.

In industry jargon, these fuels are called “stinky” or “smelly.”

We can say with a high degree of confidence that if the launch vehicle has “smelly” engines, then “before marriage” it was a combat missile (ICBM, SLBM or missile defense system - which is already a rarity). Chemistry in the service of both the army and civilians.

The only exception, perhaps, is the Ariane launch vehicle - the creation of a cooperative: Aérospatiale, Matra Marconi Space, Alenia, Spazio, DASA, etc. It suffered a similar military fate in its “girlhood”.

Almost all of the military switched to solid propellant rocket engines, as they were more convenient to use. The niche for “smelly” fuels in astronautics has narrowed to use in spacecraft propulsion systems, where long-term storage is required without special material or energy costs.
Perhaps the overview can be briefly expressed graphically:

Rocket scientists are also actively working with methane. There are no particular operational difficulties: it allows you to raise the pressure in the chamber quite well (up to 40 M Pa) and get good performance.
() and other natural gases (LNG).

I will write about other areas for improving the performance of liquid-propellant rocket engines (metallization of fuels, use of He 2, acetam, etc.) later. If there is interest.

Using the free radical effect is a good prospect.
Detonation combustion is an opportunity for the long-awaited jump to Mars.

Afterword:

in general, all rocket technical complexes (except for scientific and technological complexes), as well as attempts to make them at home, are very dangerous. I suggest you read carefully:
. The mixture, which he was preparing on the stove in a saucepan, exploded as expected. As a result, the man received a huge number of burns and spent five days in the hospital.

All home (garage) manipulations with such chemical components are extremely dangerous and sometimes illegal. It is BETTER not to approach the places where they spill without a protective equipment and a gas mask:

Just like with spilled mercury: call the Ministry of Emergency Situations, they will quickly come and professionally pick up everything.

Thank you to everyone who was able to endure it all to the end.

Primary sources:
Kachur P. I., Glushko A. V. "Valentin Glushko. Designer of rocket engines and space systems", 2008.
G.G. Gahun "Design and design of liquid rocket engines", Moscow, "Mechanical Engineering", 1989.
Possibility of increasing the specific impulse of a liquid-propellant rocket engine
when adding helium to the combustion chamber S.A. Orlin MSTU named after. N.E. Bauman, Moscow
M.S. Shekhter. "Fuels and working fluids of rocket engines", Mechanical Engineering" 1976
Zavistovsky D.I. "Conversations about rocket engines."
Philip Terekhov @lozga (www.geektimes.ru).
"Types of fuels and their characteristics. Fuel is a flammable substance used to produce heat. Composition of the fuel. Combustible part - carbon C-hydrogen H-sulfur." ​​- presentation by Oksana Kaseeva
Fakas S.S. "Fundamentals of liquid propellant engines. Working fluids"
Photos and video materials were used from the sites:

http://technomag.bmstu.ru
www.abm-website-assets.s3.amazonaws.com
www.free-inform.ru
www.rusarchives.ru
www.epizodsspace.airbase.ru
www.polkovnik2000.narod.ru
www.avia-simply.ru
www.arms-expo.ru
www.npoenergomash.ru
www.buran.ru
www.fsmedia.imgix.net
www.wikimedia.org
www.youtu.be
www.cdn.tvc.ru
www.commi.narod.ru
www.dezinfo.net
www.nasa.gov
www.novosti-n.org
www.prirodasibiri.ru
www.radikal.ru
www.spacenews.com
www.esa.int
www.bse.sci-lib.com
www.kosmos-x.net.ru
www.rocketpolk44.narod.ru
www.criotehnika.ru
www.transtank.rf
www.chistoprudov.livejournal.com/104041.html
www.cryogenmash.ru
www.eldeprocess.ru
www.chemistry-chemists.com
www.rusvesna.su
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www.armedman.ru
www.transtank.rf
www.ec.europa.eu
www.mil.ru
www.kbkha.ru
www.naukarus.com

The issue of reducing the cost of launch vehicles has always been raised. During the space race, the USSR and the USA thought little about the costs - the prestige of the country was immeasurably more expensive. Today, cutting costs “on all fronts” has become a global trend. Fuel makes up only 0.2...0.3% of the cost of the entire launch vehicle, but in addition to the cost of fuel, another important parameter is its availability. And here there are already questions. Over the past 50 years, the list of liquid fuels widely used in the rocket and space industry has changed little. Let's list them: kerosene, hydrogen and heptyl. Each of them has its own characteristics and is interesting in its own way, but they all have at least one serious drawback. Let's look at each of them briefly.

Kerosene

It began to be used back in the 50s and remains in demand to this day - it is on it that our Angara and Falcon 9 fly from SpaceX. It has many advantages, including: high density, low toxicity, provides a high specific impulse, and so far an acceptable price. But the production of kerosene today is fraught with great difficulties. For example, Soyuz rockets, which are made in Samara, now fly on artificially created fuel, because initially only certain types of oil from specific wells were used to create kerosene for these rockets. This is mainly oil from the Anastasievsko-Troitskoye field in the Krasnodar Territory. But oil wells are being depleted, and the kerosene used today is a mixture of compositions that are extracted from several wells. The coveted RG-1 brand is obtained through expensive distillation. According to experts, the problem of kerosene shortage will only get worse.

"Angara 1.1" on a kerosene engine RD-193

Hydrogen

Today, hydrogen, along with methane, is one of the most promising rocket fuels. It flies several modern rockets and upper stages at once. Paired with oxygen, it (after fluorine) produces the highest specific impulse and is ideal for use in the upper stages of a rocket (or upper stages). But its extremely low density does not allow it to be fully used for the first stages of rockets. It has one more drawback - high cryogenicity. If the rocket is fueled with hydrogen, it is at a temperature of about 15 Kelvin (-258 Celsius). This leads to additional costs. Compared to kerosene, the availability of hydrogen is quite high and its production is not a problem.

"Delta-IV Heavy" on RS-68A hydrogen engines

Heptyl

It is also known as UDMH or unsymmetrical dimethylhydrazine. This fuel still has areas of application, but it is gradually fading into the background. And the reason for this is its high toxicity. It has energy indicators almost the same as kerosene and is a high-boiling component (stored at room temperature) and, therefore, was used quite actively in Soviet times. For example, the Proton rocket flies on a highly toxic pair of heptyl + amyl, each of which is capable of killing a person who inhales their vapor through negligence. The use of such fuels in modern times is unjustified and unacceptable. The fuel is used in satellites and interplanetary probes, where, unfortunately, it is indispensable.

"Proton-M" on heptyl engines RD-253

Methane as an alternative

But is there a fuel that will satisfy everyone and cost the least? Perhaps it's methane. The same blue gas that some of you used to cook your food today. The proposed fuel is promising, is being actively developed by other industries, has a wider raw material base compared to kerosene and is low in cost - this is an important point, given the predicted problems of kerosene production. Methane, both in density and efficiency, is between kerosene and hydrogen. There are many ways to produce methane. The main source of methane is natural gas, which consists of 80..96% methane. The rest is propane, butane and other gases of the same series, which do not need to be removed at all; they are very similar in properties to methane. In other words, you can simply liquefy natural gas and use it as rocket fuel. Methane can also be obtained from other sources, for example, by processing animal waste. The possibility of using methane as rocket fuel has been considered for decades, but now there are only bench-scale options and experimental samples of such engines. For example, in Khimki NPO "Energomash" Research into the use of liquefied gas in engines has been conducted since 1981. The concept currently being developed at Energomash provides for the development of a single-chamber engine with a thrust of 200 tons using liquid oxygen - liquefied methane fuel for the first stage of a promising light-class carrier. Space technology of the near future promises to be reusable. And here another advantage of methane opens up. It is cryogenic, which means that it is enough to heat the engine to at least a temperature of -160 Celsius (or better yet, higher) and the engine itself will free itself from fuel components. According to experts, it is most suitable for creating reusable launch vehicles. This is what the chief designer thinks about methane NPO "Energomash" Vladimir Chvanov:

The specific impulse of an LNG engine is high, but this advantage is offset by the fact that methane fuel has a lower density, so the total energy advantage is insignificant. From a design point of view, methane is attractive. To free the engine cavities, you only need to go through an evaporation cycle - that is, the engine is more easily freed from product residues. Due to this, methane fuel is more acceptable from the point of view of creating a reusable engine and a reusable aircraft.

Another argument in favor of using methane is the ability to extract it from asteroids, planets and their satellites, providing fuel for return missions. It is much easier to extract methane there than kerosene. Naturally, the possibility of bringing fuel with you is out of the question. The prospect of such long-distance missions is very distant, but some work is already underway.

A future that never came

So why has methane never become a practically used fuel in Russia? The answer is quite simple. Since the beginning of the 80s, not a single new rocket engine has been created in the USSR, and then in Russia. All Russian “new products” are modernization and renaming of the Soviet legacy. The only honestly created complex - "Angara" - was planned from the very beginning as a kerosene transport. Remaking it will cost a pretty penny. In general, Roscosmos constantly rejects methane projects because it associates the “good” for at least one such project with the “good” for a complete restructuring of the industry from kerosene and heptyl to methane, which is considered a long and expensive undertaking.

Engines

At the moment, there are several companies announcing the imminent use of methane in their rockets. Engines that are being created:

• KVRD FRE-1 from Firefly Space Systems ;
• Blue Engine 4 (BE-4) from Blue Origin;
• S5.86 from KBKhM im. Isaeva;
• Raptor (Merlin 2?) from SpaceX ;
• So far unnamed engine from NPO "Energomash" based on their universal rocket camera;
• RD0110MD, RD0162, created in Chemical Automatics Design Bureau.

FRE-1/

Fuel for liquid rocket engines used as part of space upper stages and launch vehicle stages contains methane-based fuel and an oxidizer, while the fuel used is a mixture of methane and ethylene with a methane molar content of 5 to 25%. The use of the proposed fuel on medium-class launch vehicles with a total fuel reserve of 300 tons will reduce the mass of the launch vehicle structure compared to the use of methane + oxygen fuel by ~2%, which is equivalent to an increase in the mass of the launched payload by ~6.5%. Compared to using kerosene + oxygen fuel, the mass of the launched payload will increase by ~ 7.5%.

The proposed fuel is intended for use in liquid rocket engines (LPRE) used as part of space upper stages (UB) and stages of launch vehicles (LV). An analogue of this fuel is kerosene + oxygen fuel. Liquid oxygen is currently one of the most common oxidizers in liquid propellant rocket engines. This is due to the fact that liquid oxygen is an environmentally friendly fuel component. At the same time, it is cheap, non-toxic, moderately flammable and provides fairly high energy characteristics of fuels. For example, kerosene + oxygen fuel at a pressure in the combustion chamber of 70 ata and a geometric expansion ratio of the nozzle of 40 provides a specific void impulse ~ 8% greater than kerosene + AT fuel, where nitrogen tetroxide is used as an oxidizer. Kerosene is a hydrocarbon fuel, which is a mixture of natural hydrocarbons obtained during the distillation of oil. The production of kerosene from natural oil makes it relatively cheap. In addition, kerosene is a low-toxic substance belonging to the 4th (lowest) hazard class, is moderately flammable and has a fairly high density, which has a positive effect on its operational advantages. In general, kerosene + oxygen fuel is an effective fuel with a fairly high density of ~ 1000 kg/m 3 and a fairly high specific impulse of the outflow of its combustion products, which makes it possible to quite effectively solve existing problems facing modern launch vehicles. The disadvantages of kerosene + oxygen fuel include: a relatively large difference in the operating temperatures of liquid oxygen (~ 90 K) and kerosene (~ 290 K), which requires taking special measures to compensate for the temperature stresses that arise in the oxidizer storage tank when filling it with liquid oxygen, and the need to use component storage tanks with separate bottoms and significant thermal insulation between the tanks. This leads to a significant increase in the mass of the component storage tanks and to an increase in the volume occupied by the fuel component storage tanks in the propulsion system, which also increases the mass costs of fuel storage. The prototype of the proposed fuel is methane+oxygen fuel. Methane is the main constituent of natural gases, so its production is estimated to be even cheaper than kerosene production. In terms of energy characteristics, this fuel is superior to kerosene + oxygen fuel: at the above pressures in the combustion chamber and the geometric degree of expansion of the nozzle, the specific impulse of methane + oxygen fuel will be higher than the specific impulse of kerosene + oxygen fuel by ~ 4%. However, methane, even at a temperature of 91 K (its melting point is 90.66 K), has a low density of 455 kg/m 3, while the density of methane + oxygen fuel is only 830 kg/m 3, which leads to an increase in mass costs for its storage due to the need increasing the volume of component storage tanks. The low density of methane + oxygen fuel and the impossibility of supercooling oxygen when using fuel component storage tanks with combined bottoms lead to the fact that for space RBs the time of possible fuel storage in near-Earth space is significantly reduced (by 20% compared to kerosene + oxygen). Since the melting point of methane is higher than the boiling point of oxygen at a pressure of 1 ata (i.e., above 90 K), the use of fuel component storage tanks with combined bottoms even for oxygen boiling at 1 ata (and even more so when using supercooled oxygen, which boils at lower pressure) is impossible without the use of inter-tank thermal insulation. In addition, since the fuel tank is filled with cryogenic methane, it must be thermally insulated from external heat inflows, which further increases the mass costs of fuel storage. All this leads to a significant increase in the mass and dimensions of methane + oxygen fuel storage tanks compared to kerosene + oxygen fuel, which significantly, and in some cases down to zero, reduces the effect that could be obtained from the higher specific impulse of the prototype. The objective of the invention is to increase the density of fuel and, as a consequence, the mass costs of storing it in fuel tanks. The energy characteristics of the fuel do not deteriorate compared to the prototype. This is achieved by using fuel containing fuel and an oxidizer, where a mixture of methane and ethylene with a methane molar content of 5 to 25% is used as fuel. At the specified methane content, the solidification temperature of such fuel is less than 90 K, i.e. when using boiling liquid oxygen as an oxidizer, for example, the oxidizer and fuel tanks may have a common bottom that is not covered with thermal insulation. In addition, the proposed fuel for the specified range of the methane-ethylene molar ratio will have a density from 900 to 970 kg/cm 3, which is comparable to the density of kerosene + oxygen fuel, and taking into account the high heat capacity of the fuel in the proposed fuel, the possible residence time of space RBs in the near-Earth space will be the same as when using kerosene + oxygen fuel. At the same time, thermodynamic calculations showed that the specific impulse of the exhaust products of the proposed fuel will be the same as for methane + oxygen fuel. The use of the proposed fuel on a medium-class launch vehicle with a total fuel reserve of 300 tons will reduce the weight of the launch vehicle structure compared to the use of methane + oxygen fuel by ~ 2%, which is equivalent to an increase in the mass of the launched payload by ~ 6.5%. Compared to using kerosene+oxygen fuel, the mass of the launched payload will increase by ~ 7.5%. Methane, as noted above, is the main component of natural gases, and ethylene is a widespread raw material for the chemical industry (for example, in the production of polyethylene), so the production of fuel for such fuel will not require the creation of new production facilities and can be developed in a fairly short time. The cost of the proposed fuel is estimated to be comparable to the cost of kerosene + oxygen fuel. LIST OF REFERENCES USED 1. Fundamentals of the theory and calculation of liquid rocket engines / in 2 books / ed. V. M. Kudryavtseva, ed. 4th revision and additional - M. "Higher School", 1993. - book 1, pp. 130-134. 2. Paushkin Ya. M. Chemical composition and properties of jet fuels. - M. Publishing House of the USSR Academy of Sciences, 1958. - 376 p., ill. p.302. 3. Sinyarev G.B. Liquid rocket engines. - M. State Publishing House of the Defense Industry. 1955. -488 pp., ill. pp. 159 - 161. 4. Handbook on the physical and technical foundations of cryogenics. / M.P. Malkov. - 3rd ed., revised. and additional - M.: Energoatomizdat, 1985, -432 p., ill. p.217. 5. Handbook on the separation of gas mixtures by the deep cooling method. /AND. I. Gelperin. - 2nd ed., revised. - M. State Scientific and Technical Publishing House of Chemical Literature, 1963. - 512 p., ill. p.232. 6. Thermodynamic and thermophysical properties of combustion products / in 3 volumes / ed. V.P. Glushko, - M. All-Union Institute of Scientific and Technical Information. 1968, vol. 2, pp. 177-308.

Claim

Fuel for liquid rocket engines containing methane-based fuel and an oxidizer, characterized in that a mixture of methane and ethylene with a methane molar content of 5 to 25% is used as fuel.

Similar patents:

The invention relates to a method of operation of an aircraft engine operating on the principle of jet propulsion

The invention relates to rocket and space technology and concerns the design of liquid rocket engines (LPRE) operating on cryogenic fuel, in particular engines of rocket units and spacecraft using cryogenic oxidizer liquid oxygen and hydrocarbon fuel as fuel components

In no way do we belittle the merits of the great K.E. Tsiolkovsky, but he was still a rocket science theorist. Today we would like to mention the man who was the first to build a rocket using liquid fuel. And even though this rocket rose only 12 meters, it was only the first small step of humanity on the long road to the stars.
March 16 marked 90 years since the launch of the first liquid fuel rocket in history. Let us emphasize that this is precisely the first “in history” launch. It is quite logical to assume that since the invention of gunpowder by the Chinese, there have been countless attempts to launch certain objects into the sky using gunpowder or anything else, but little is known about them today. For example, there are records of Chinese engineers using gunpowder to repel enemy attacks as early as the 13th century. Therefore, we note what we know for sure.
Today, the launch of a rocket, be it liquid or solid fuel, would not surprise even a first-grader, but 90 years ago it was an innovation akin to the discovery of gravitational waves today. On March 16, 1926, a rocket using liquid fuel, a mixture of gasoline and oxygen, was launched by American rocket pioneer Robert Goddard.
We found an animation (below) online of NASA Goddard Space Flight Center celebrating the 50th anniversary of the small rocket's historic test flight in 1976.
Employees of the center named after Goddard gathered in front of a school bus at NASA to watch the launch of a replica of the world's first liquid-fuel rocket. Today, liquid-fuel rockets are used in most major space launches, from manned flights to interplanetary missions.
However, the first rocket was very small and flew low. But despite this, it marked a big leap in the development of rocket technology.

Animation of the launch of Robert Goddard's replica rocket on the occasion of the 50th anniversary of the first launch (March 16, 1976).
Photo: NASA/Goddard Space Flight Center

Goddard believed that liquid fuels were the future. Such fuel, for example, provides more thrust per unit of fuel and allows engineers to use less powerful pumps for delivery, due to the higher density of the liquid compared to gases or the same gunpowder. However, it took Goddard as many as 17 years of continuous work to bring the matter to the first launch.
Goddard dreamed of witnessing the first interplanetary journey. This did not happen, he died in 1945, but his life’s work continues, the descendants of his brainchild are conquering space paths, albeit with varying success.
The first satellite was launched by the Soviet Union in 1957 using a liquid-fuel rocket. Liquid fuel was also used to power the huge Saturn V rockets that carried astronauts to the Moon in the 60s and 70s. Liquid fuel is still preferred for manned missions today because its combustion can be controlled, which is safer than using solid rocket fuel.
Other rockets that use liquid fuel include the European Ariane 5 launch vehicle (which will launch the James Webb Telescope), the Russian Soyuz, Atlas V and Delta from United Launch Alliance, as well as Falcon 9 and SpaceX.
Goddard owns more than 200 patents for various inventions. One of his main works is multi-stage rockets, which are currently the main workhorses of all countries' space programs.
For all his merits, as one NASA report puts it, “The United States did not fully recognize his (Goddard’s) potential during his lifetime, and some of his ideas about the conquest of outer space were ridiculed. But the flight of the first liquid-fuel rocket is as significant for space as the Wright brothers' first flight for aviation, and even 90 years later, his inventions are still an integral part of space technology."

Rocket Engines

Abstract completed

9B grade student

Kozhasova Indira

introduction. 2

purpose and types of rocket engines. 2

Thermochemical rocket engines. 3

Nuclear rocket engines. 6

other types of rocket engines. 8

Electric rocket engines. 9

References. 10

A rocket engine is a jet engine that does not use the environment (air, water) for operation. Chemical rocket engines are the most widely used. Other types of rocket engines are being developed and tested - electric, nuclear and others. The simplest rocket engines running on compressed gases are also widely used on space stations and vehicles. Typically, they use nitrogen as a working fluid.

According to their purpose, rocket engines are divided into several main types: accelerating (starting), braking, propulsion, control and others. Rocket engines are primarily used on rockets (hence the name). In addition, rocket engines are sometimes used in aviation. Rocket engines are the main engines in astronautics.

Based on the type of fuel (working fluid) used, rocket engines are divided into:

Solid fuel

Liquid

Military (combat) missiles usually have solid propellant motors. This is due to the fact that such an engine is refueled at the factory and does not require maintenance for the entire storage and service life of the rocket itself. Solid propellant engines are often used as boosters for space rockets. They are used especially widely in this capacity in the USA, France, Japan and China.

Liquid rocket engines have higher thrust characteristics than solid rocket engines. Therefore, they are used to launch space rockets into orbit around the Earth and for interplanetary flights. The main liquid fuels for rockets are kerosene, heptane (dimethylhydrazine) and liquid hydrogen. For such types of fuel, an oxidizer (oxygen) is required. Nitric acid and liquefied oxygen are used as oxidizers in such engines. Nitric acid is inferior to liquefied oxygen in terms of oxidizing properties, but does not require maintaining a special temperature regime during storage, refueling and use of rockets.

Engines for space flights differ from those on Earth in that they must produce as much power as possible with the smallest possible mass and volume. In addition, they are subject to such requirements as exceptionally high efficiency and reliability, and significant operating time. Based on the type of energy used, spacecraft propulsion systems are divided into four types: thermochemical, nuclear, electric, solar-sail. Each of the listed types has its own advantages and disadvantages and can be used in certain conditions.

Currently, spaceships, orbital stations and unmanned Earth satellites are launched into space by rockets equipped with powerful thermochemical engines. There are also miniature engines with low thrust. This is a smaller copy of powerful engines. Some of them can fit in the palm of your hand. The thrust of such engines is very small, but it is enough to control the position of the ship in space.

It is known that in an internal combustion engine, the furnace of a steam boiler - wherever combustion occurs, atmospheric oxygen takes the most active part. There is no air in outer space, and for rocket engines to operate in outer space, it is necessary to have two components - fuel and oxidizer.

Liquid thermochemical rocket engines use alcohol, kerosene, gasoline, aniline, hydrazine, dimethylhydrazine, and liquid hydrogen as fuel. Liquid oxygen, hydrogen peroxide, and nitric acid are used as an oxidizing agent. Perhaps in the future liquid fluorine will be used as an oxidizing agent when methods for storing and using such an active chemical are invented.

Fuel and oxidizer for liquid jet engines are stored separately in special tanks and supplied to the combustion chamber using pumps. When they are combined in the combustion chamber, temperatures reach 3000 – 4500 °C.

Combustion products, expanding, acquire speeds from 2500 to 4500 m/s. Pushing off from the engine body, they create jet thrust. At the same time, the greater the mass and speed of gas flow, the greater the thrust of the engine.

The specific thrust of engines is usually estimated by the amount of thrust created per unit mass of fuel burned in one second. This quantity is called the specific impulse of a rocket engine and is measured in seconds (kg thrust / kg burnt fuel per second). The best solid propellant rocket engines have a specific impulse of up to 190 s, that is, 1 kg of fuel burning in one second creates a thrust of 190 kg. A hydrogen-oxygen rocket engine has a specific impulse of 350 s. Theoretically, a hydrogen-fluorine engine can develop a specific impulse of more than 400 s.

The commonly used liquid rocket engine circuit works as follows. Compressed gas creates the necessary pressure in tanks with cryogenic fuel to prevent the occurrence of gas bubbles in pipelines. Pumps supply fuel to rocket engines. Fuel is injected into the combustion chamber through a large number of injectors. An oxidizer is also injected into the combustion chamber through the nozzles.

In any car, when fuel burns, large heat flows are formed that heat the walls of the engine. If you do not cool the walls of the chamber, it will quickly burn out, no matter what material it is made of. A liquid jet engine is typically cooled by one of the fuel components. For this purpose, the chamber is made of two walls. The cold component of the fuel flows in the gap between the walls.

Greater traction is created by an engine running on liquid oxygen and liquid hydrogen. In the jet stream of this engine, gases rush at a speed of slightly more than 4 km/s. The temperature of this jet is about 3000°C, and it consists of superheated water vapor, which is formed by the combustion of hydrogen and oxygen. Basic data on typical fuels for liquid jet engines are given in Table No. 1

But oxygen, along with its advantages, also has one drawback - at normal temperatures it is a gas. It is clear that it is impossible to use oxygen gas in a rocket because in this case it would have to be stored under high pressure in massive cylinders. Therefore, Tsiolkovsky, who was the first to propose oxygen as a component of rocket fuel, spoke of liquid oxygen as a component without which space flights would not be possible.

To turn oxygen into liquid, it must be cooled to a temperature of -183°C. However, liquefied oxygen evaporates easily and quickly, even if it is stored in special heat-insulated vessels. Therefore, it is impossible to keep a rocket equipped for a long time, the engine of which uses liquid oxygen as an oxidizer. The oxygen tank of such a rocket must be refilled immediately before launch. While this is possible for space and other civilian rockets, it is unacceptable for military rockets that need to be kept ready for immediate launch for a long time. Nitric acid does not have this disadvantage and is therefore a “conserving” oxidizing agent. This explains its strong position in rocket technology, especially military, despite the significantly lower thrust it provides.

The use of the most powerful oxidizing agent known to chemistry, fluorine, will significantly increase the efficiency of liquid-propellant jet engines. However, liquid fluorine is very inconvenient to use and store due to its toxicity and low boiling point (-188°C). But this does not stop rocket scientists: experimental fluorine engines already exist and are being tested in laboratories and experimental benches.

Soviet scientist F.A. Back in the thirties, Zander in his works proposed using light metals as fuel in interplanetary flights, from which the spacecraft would be made - lithium, beryllium, aluminum, etc., especially as an additive to conventional fuel, for example hydrogen-oxygen. Such “triple compositions” are capable of providing the highest possible exhaust velocity for chemical fuels – up to 5 km/s. But this is practically the limit of chemical resources. She practically cannot do more.

Although the proposed description is still dominated by liquid rocket engines, it must be said that the first in the history of mankind was created a thermochemical rocket engine using solid fuel - solid propellant rocket engine.

Fuel - such as special gunpowder - is located directly in the combustion chamber. A combustion chamber with a jet nozzle filled with solid fuel - that’s the whole structure. The combustion mode of solid fuel depends on the purpose of the solid propellant rocket engine (starter, sustainer or combined). Solid propellant missiles used in military affairs are characterized by the presence of starting and sustaining engines. The launch solid propellant rocket engine develops high thrust for a very short time, which is necessary for the missile to leave the launcher and for its initial acceleration. The sustainer solid propellant rocket motor is designed to maintain a constant flight speed of the rocket on the main (propulsion) section of the flight path. The differences between them lie mainly in the design of the combustion chamber and the profile of the combustion surface of the fuel charge, which determine the rate of fuel combustion on which the operating time and engine thrust depend. Unlike such rockets, space launch vehicles for launching Earth satellites, orbital stations and spacecraft, as well as interplanetary stations operate only in the launch mode from the launch of the rocket until the object is launched into orbit around the Earth or onto an interplanetary trajectory.

In general, solid propellant rocket engines do not have many advantages over liquid fuel engines: they are easy to manufacture, can be stored for a long time, are always ready for action, and are relatively explosion-proof. But in terms of specific thrust, solid fuel engines are 10-30% inferior to liquid engines.

One of the main disadvantages of rocket engines running on liquid fuel is associated with the limited flow rate of gases. In nuclear rocket engines, it seems possible to use the colossal energy released during the decomposition of nuclear “fuel” to heat the working substance.

The operating principle of nuclear rocket engines is almost no different from the operating principle of thermochemical engines. The difference is that the working fluid is heated not due to its own chemical energy, but due to “extraneous” energy released during an intranuclear reaction. The working fluid is passed through a nuclear reactor, in which the fission reaction of atomic nuclei (for example, uranium) occurs, and is heated.

Nuclear rocket engines eliminate the need for an oxidizer and therefore only one liquid can be used.

As a working fluid, it is advisable to use substances that allow the engine to develop greater traction force. This condition is most fully satisfied by hydrogen, followed by ammonia, hydrazine and water.

The processes in which nuclear energy is released are divided into radioactive transformations, fission reactions of heavy nuclei, and fusion reactions of light nuclei.

Radioisotope transformations are realized in so-called isotope energy sources. The specific mass energy (the energy that a substance weighing 1 kg can release) of artificial radioactive isotopes is significantly higher than that of chemical fuels. Thus, for 210 Po it is equal to 5*10 8 KJ/kg, while for the most energy-efficient chemical fuel (beryllium with oxygen) this value does not exceed 3*10 4 KJ/kg.

Unfortunately, it is not yet rational to use such engines on space launch vehicles. The reason for this is the high cost of the isotopic substance and operational difficulties. After all, the isotope constantly releases energy, even when it is transported in a special container and when the rocket is parked at the launch site.

Nuclear reactors use more energy-efficient fuel. Thus, the specific mass energy of 235 U (the fissile isotope of uranium) is equal to 6.75 * 10 9 KJ/kg, that is, approximately an order of magnitude higher than that of the 210 Po isotope. These engines can be “turned on” and “off”; nuclear fuel (233 U, 235 U, 238 U, 239 Pu) is much cheaper than isotope fuel. In such engines, not only water can be used as a working fluid, but also more efficient working substances - alcohol, ammonia, liquid hydrogen. The specific thrust of an engine with liquid hydrogen is 900 s.

In the simplest design of a nuclear rocket engine with a reactor running on solid nuclear fuel, the working fluid is placed in a tank. The pump supplies it to the engine chamber. Sprayed using nozzles, the working fluid comes into contact with the fuel-generating nuclear fuel, heats up, expands and is thrown out at high speed through the nozzle.

Nuclear fuel is superior in energy reserves to any other type of fuel. Then a logical question arises: why do installations using this fuel still have a relatively low specific thrust and a large mass? The fact is that the specific thrust of a solid-phase nuclear rocket engine is limited by the temperature of the fissile material, and the power plant during operation emits strong ionizing radiation, which has a harmful effect on living organisms. Biological protection against such radiation is very important and is not applicable on spacecraft.

Practical development of nuclear rocket engines using solid nuclear fuel began in the mid-50s of the 20th century in the Soviet Union and the USA, almost simultaneously with the construction of the first nuclear power plants. The work was carried out in an atmosphere of increased secrecy, but it is known that such rocket engines have not yet received real use in astronautics. Everything has so far been limited to the use of isotopic sources of electricity of relatively low power on unmanned artificial Earth satellites, interplanetary spacecraft and the world famous Soviet “lunar rover”.

There are also more exotic designs for nuclear rocket engines, in which the fissile material is in a liquid, gaseous or even plasma state, but the implementation of such designs at the current level of technology and technology is unrealistic.

The following rocket engine projects exist, still at the theoretical or laboratory stage:

Pulse nuclear rocket engines using the energy of explosions of small nuclear charges;

Thermonuclear rocket engines, which can use a hydrogen isotope as fuel. The energy productivity of hydrogen in such a reaction is 6.8 * 10 11 KJ/kg, that is, approximately two orders of magnitude higher than the productivity of nuclear fission reactions;

Solar-sailing engines - which use the pressure of sunlight (solar wind), the existence of which was experimentally proven by the Russian physicist P.N. Lebedev back in 1899. By calculation, scientists have established that a device weighing 1 ton, equipped with a sail with a diameter of 500 m, can fly from Earth to Mars in about 300 days. However, the efficiency of a solar sail decreases rapidly with distance from the Sun.

Almost all of the rocket engines discussed above develop enormous thrust and are designed to launch spacecraft into orbit around the Earth and accelerate them to cosmic speeds for interplanetary flights. A completely different matter is propulsion systems for spacecraft already launched into orbit or on an interplanetary trajectory. Here, as a rule, you need low-power motors (several kilowatts or even watts) capable of operating for hundreds and thousands of hours and being switched on and off repeatedly. They allow you to maintain flight in orbit or along a given trajectory, compensating for the flight resistance created by the upper layers of the atmosphere and the solar wind.

In electric rocket engines, the working fluid is accelerated to a certain speed by heating it with electrical energy. Electricity comes from solar panels or a nuclear power plant. Methods for heating the working fluid are different, but in reality, electric arc is mainly used. It has proven to be very reliable and can withstand a large number of starts. Hydrogen is used as a working fluid in electric arc motors. Using an electric arc, hydrogen is heated to a very high temperature and it turns into plasma - an electrically neutral mixture of positive ions and electrons. The speed of plasma outflow from the engine reaches 20 km/s. When scientists solve the problem of magnetic isolation of plasma from the walls of the engine chamber, then it will be possible to significantly increase the temperature of the plasma and increase the exhaust speed to 100 km/s.

The first electric rocket engine was developed in the Soviet Union in 1929-1933. under the leadership of V.P. Glushko (later he became the creator of engines for Soviet space rockets and an academician) in the famous gas dynamic laboratory (GDL).

1. Soviet encyclopedic dictionary

2. S.P. Umansky. Cosmonautics today and tomorrow. Book For students.