Launch System

Saturn V launch
Saturn V launch

Saturn V compared to N1

A launch system includes the launch vehicle or vehicles, the launch pad, and other infrastructure. For the US Apollo program to the Moon the launch system included a Saturn V rocket and launch pad 39 at Kennedy Space Center. For the USSR Zond program to the Moon the launch system included a Proton UR-500 rocket from the Baikonur Cosmodrome. For the USSR N1/L3 program to the Moon the launch system would have included an N1 rocket from the Baikonur Cosmodrome.

All of these launch systems used liquid propellants, but they didn't use the same propellants. The Saturn V first stage was fuelled by RP-1 (a mixture) and liquid oxygen or LOX (O2). The second and third stages were fuelled by liquid hydrogen (H2) and liquid oxygen or LOX (O2). The Proton is fuelled by very toxic unsymmetrical dimethyl hydrazine or UDMH (H2NN(CH3)2) and dinitrogen tetroxide (N2O4) which ignite on contact. The N1 was to be fuelled by RP-1 and liquid oxygen or LOX.

In addition to Apollo, Zond, and N1/L3 programs, other launch systems have successfully launched autonomous spacecraft that safely landed on the Moon or went into orbit around the Moon. These include the Atlas Centaur, Molniya-M, Delta II 792X, Atlas V, Long March, and others.

These launch systems also used liquid propellants. They mostly use the same combinations of propellants as the Saturn, Proton, and N1, although some used Aerozine (A-50) rather than unsymmetrical dimethyl hydrazine (UDMH). However, in addition to liquid propellants, some of these launch systems used solid propellant rockets. These solid propellant rockets quite often used powdered aluminium as a fuel, but might use magnesium or zinc. Additionally they will have an elastomer binder such as hydroxyl-terminated polybutadiene (HTPB) or polybutadiene acrylic acid acrylonitrile prepolymer (PBAN) both of which additionally act as lower energy fuels. For an oxidizer they most often use ammonium perchlorate (AP), thus being refered to as ammonium perchlorate composite propellants (APCP). Solid propellant rockets generate lower specific impulse (Isp) than liquid propellant rockets. While liquid hydrogen and LOX might have an Isp of 450, and RP-1 and LOX might have an Isp of 350, a solid propellant rocket might have an Isp of 250.

Launch systems used for Lunar missions
Launch Vehicle mission type country of development payload to GTO (kg)
Ariane 5G Lunar orbit Europe 6,950
Athena II Lunar orbit USA 593
Atlas SLV-3 Agena-D Lunar orbit USA 700
Atlas SLV-3C Centaur-D Lunar landing USA 2,222
Atlas V 401 Lunar orbit USA 4,950
Chang Zheng 3 aka Long March 3A Lunar orbit China 2,600
Delta II 792X Lunar orbit USA 1,819
H-IIA Lunar orbit Japan 4,100 to 6,000
Chang Zheng 3B aka Long March 3B Lunar landing China 5,100
Minotaur V Lunar orbit USA 532
Molniya-M Lunar landing USSR, Russia 1,600
Mu-3S-II Lunar orbit Japan 520
UR-500K aka Proton-K/D Lunar landing USSR, Russia 4,930
PSLV-XL Lunar orbit India 1,425
Saturn V Lunar landing USA 48,600 to TLI
Titan II(23)G Lunar orbit USA ~ 3,000 ?

In addition to the rocket propellants, a launch vehicle has chemical rocket engines that burns the propelants creating a lot of pressure in the rocket engine combustion chamger. This pressurized gas is guided by the rocket engine nozzle into a high-speed exhaust stream which causes the rocket acceleration. While a liquid propellant rocket engine may use pumps to feed the propellants into the combustion chamber, solid propellant rocket engine combustion chambers are formed out of the solid propellant itself.

Rockets use various methods to compensate for air turbulance and adjust their direction of flight. This might include fins on the outside of the rocket, vanes in the engine exhaust stream, or gimballed engines which can change the direction of the nozzle. To control these mechanisms the rocket might have an electronic guidance system. The Saturn V had a section called the Saturn V Instrument Unit. This unit included the ST-124-M3 inertial platform, and the launch vehicle digital computer (LVDC). Note that the LVDC is not the same as the Apollo Guidance Computer (AGC) which was used both in the Apollo Command Module and in the Apollo Lunar Module.

The Delta II booster is controlled by the second-stage avionics system which provides guidance, flight control, and vehicle sequencing functions during the booster and second-stage phases of flight.

Working Example

For students who want to experiment with a working example, you probably shouldn't be experimenting with LOX and certainly not with UDMH nor dinitrogen tetroxide, so if you want to experiment with rockets, what should you do? As mentioned above, in addition to liquid propellants, rockets can use solid propellants. The Space Shuttle used two solid propellant boosters, and the Titan IIIE Centaur, Delta II 7925, and Atlas V 541 also used solid propellant rockets along with their liquid propellant rockets. The Scout launch system was the first orbital launch vehicle to be entirely composed of solid propellant rockets. More recent launch vehicles that use mostly or all solid propellant rockets to launch spacecraft into orbit around the Moon include the Athena II, Minotaur V, and Mu-3S-II. The Minotaur V is a 5 stage launch vehicle composed entirely of solid propellant rockets, and it's first launch was used to put the Lunar Atmosphere and Dust Environment Explorer (LADEE) into lunar orbit.

Many lower power solid propellant rocket engines are available commercially. These can be fuelled with black-powder or with ammonium perchlorate composite propellants similar to what was used in the solid propellant rockets of the Space Shuttle. Some sources of solid propellant model rockets include:

Before launching your rocket, you should have an estimate of how high your rocket will go. The altitude a rocket will go depends on its velocity, the velocity depends on its acceleration, and the acceleration depends on the rocket thrust and mass. The drag of the rocket through the atmosphere also affects its altitude. Determining the altitude a rocket will go is a little hard because the mass of the rocket changes as the rocket fuel is consumed. To estimate the altitude and velocity your rocket will fly, download the Android RocketCalc app to your Android smartphone.

Link to RocketCalc for Android smartphones

Run RocketCalc and select the Options (or Parameters) menu item. Enter into RocketCalc the characteristics of your rocket and rocket engine and select OK. RocketCalc will then display the likely flight profile of your rocket. You can tap on the RocketCalc flight profile screen to find the altitude and velocity at any particular time during the rockets flight.

Instead of buying a commercially available solid propellant rocket engines, you might want to make your own rocket engine. Some examples of rocket engines you can make yourself include:

Finally, here are some links to interesting rocketry projects:

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