Rocket Motors

Kerosene and O2

• Must be pumped very fast and at a high pressure.

• Pump turbines spin at 35,000 rpm, which is twice as fast as a jet engine.

Kerosene and O2

• Temperature• The temp inside the combustion chamber has

to be extreme in order to achieve maximum thrust.

• Temp raises pressure pressure raises temp.

• As a result, a motor can only be used once.

O2 (Oxygen)

• As a gas it takes up a great deal of space.• To compress it, you need to supercool it so it

becomes a liquid. (-4000 F)• As a result, you need very strong tanks.

O2 Continued

• The system must be kept very cold because as it will expand as it heats up.

• Must bleed-off this pressure or it will explode.

O2 Drawbacks

• Tanks are very expensive because they need to be very strong but, at the same time, light.

• LOX can only be stored inside the rocket for a short period of time.

• LOX is very dangerous because it is so volatile.• (Supreme Oxidizer)

Kerosene

• Remains a liquid at room temp.• Only buns in the presence of oxygen.• It is relatively heavy and not a very big “Bang

for the Buck”

Russian R-7 (Little Seven)

• Aug. 3, 1957 flew a nuclear strike trajectory.• Two months later (Oct. 4) launched Sputnik.• Needed 3-4 hours to fill and prime• “Too Long!!”

Hydrogen/O2

• When a liquid form it is lighter and more chemically energetic than kerosene.

• Was used in the Saturn V and the main engines of the Space Shuttle.

• Space Shuttle engines are reusable. (not really)

Hydrogen/O2 Drawbacks

• Hydrogen is very difficult to keep in a liquid form.

• Since it is such a small molecule, it will leak out of even microscopic holes.

• No flaws in tank>>>>>BOOM• Welding these tanks is very difficult.• This is why the Russians lost the space race.

They could not handle H2.

Hydrogen/O2

• If hydrogen ignites when you don’t want it to, you have the destructive energy of a small atomic bomb.

• Ex. Challenger in 1986

Hypergolic Chemicals

• Chemicals that will ignite spontaneously on contact with each other.

• They are among the nastiest and most toxic substances on the planet.

Hypergolic Fuels

• Can be stored. (Sort of!)• Very corrosive so they will eat away at

anything they come in contact with.

Secret Missile R-16

• October 1960: Single Worst Rocket Disaster• Used Hypergolic Fuels (Nitric Acid &

Hydrazine) “Devil’s Venom”• On Oct. 23rd the missile was fueled for launch.• At this time, just like our launches, all

unessential personnel were supposed leave the area.

Secret Missile R-16

• Nedelin ignored the safety rules and kept around 150 military and civilian people at the pad.

• Soon after fueling, it was discovered that fuel was oozing from dozens of pipe joints and tank seams.

• The supposed “storable” fuel was not storing.

Secret Missile R-16

• Nedelin characterized the leak as acceptable.• The following day (Oct. 24) he sent even more

crew to the pad to fix the problem.• He himself, demanded a chair to sit in and sat

within 15-20 meters from the missile.• The membranes on the fuel and oxidizer lines

in the second stage had been activated to the self-igniting propellants were only one valve from the combustion chamber.

Secret Missile R-16

• An estimated 250 unsuspecting people were still around the rocket when the valve was prematurely activated.

• Instantly, the roaring flame of the second stage engine burst through the fuel tank of the first stage directly below it causing an enormous explosion of the fully fueled rocket.

Secret Missile R-16

• Many of the people close by were incinerated instantly.

• Next, the upper stage crashed down and spilled its fuel into the flames.

• The roadways and tarmac around it melted and also caught fire.

• The flames spread for 1000’s of meters engulfing everyone.

Secret Missile R-16

• Over 190 people were killed including Nedelin who was perched on his chair watching the whole thing.

Black Powder (China)

• Made from sulfur, charcoal and saltpeter (potassium nitrate).

• Clever feature is the chemical mix contains its own oxidizer as well as its own fuel.

Black Powder/Advantages

• External source of oxidizer in not necessary once it is lit.

• No super cooling of liquid, no turbo pumps or complicated pipes and valves.

• Can be stored for months or even years.• World’s simplest rocket motor.• NASA uses them for to lift heavy satellites and

the space shuttle.

Black Powder/Disadvantaages

• “All or Nothing” Once they are lit, they burn until their fuel is used up.

• They can not be throttled and can’t be shut down.

• 1986 Challenger; A solid booster sprang a small exhaust leak. It acted like a small flamethrower aimed at the shuttle’s massive hydrogen tank.

The Ideal Propulsion System

• Must be simpler than a liquid engine yet more controllable than a solid one.

Hybrid Engines

• Hybrids offer the best aspects of both.• The fuel grade is made from hydroxy-

terminated polybutatiene.• Very cheap and easy to produce.• Uses Nitrous oxide as an oxidizer which can

easily stored as a liquid as room temp.• Has the advantage of being “self pressurizing”.

Hybrid

• Nitrous turns from a liquid to a gas jet by simply opening a valve.

• No need for any pumps or expensive plumbing.

• Relatively clean burning. Exhaust is mainly water vapor, carbon monoxide and nitrogen.

Hybrid

• Virgin Galactic uses these engines in the Space Ship II and their new rocket the Launcher One

Space Ship II

Launcher One