1	Spaceflight 101 Presented By: Tyler Waldrop
2	Topics: Propulsion – Liquid VS Solid Flight Controls Power Generation Communication Life Support Launch and Orbit Re-Entry U.S. Space Flight Disasters Why? Q&A
3	Propulsion Propulsion – Liquid Fuel vs. Solid fuel.
4	Liquid Fuel Engines Liquid Fuel is by far safer and can be switched off and on at will. Liquid fuel engines can also be fully throttled by controlling the amount of liquid fuel, oxidizer and pressure in the reaction chamber. A scenario where liquid fuel is advantage over solid fuel is for a rocket flight or trajectory requiring multiple burns during the course of launch. Liquid fuel is ideal for dealing with what’s called Max-Q. A disadvantage of liquid fuel is the refrigeration and time/complexity required to load and pressurize such volatile and dangerous fuels into a spacecraft prior to launch.
5	Solid Fuel Engines Solid fuel engines (SRB’s in the shuttle program) are as the name suggests, a solid “dry” fuel. Two were used on each shuttle launch. A scenario where a solid fuel can be an advantage is when you might need to launch with no prior preparation. For example, nuclear missiles ready to launch on command inside a silo. A downside is that solid fuel can not easily be extinguished or relighted. Only recently has this been accomplished with some varied success. Solid fuel also can not be throttled. However, limited steering is possible.
6	Liquid Fuel Engine Diagram Below is a diagram of a very simplistic view of the inner workings of a liquid fuel rocket engine. As you can see, is consists of two larger tanks, a pump system, a combustion chamber, a throat and exhaust nozzle. A common fuel is RP-1 (Kerosene similar to Jet Fuel). A common oxidizer - liquid Oxygen (LOX).
7	Solid Fuel Engine Diagram To the right is a very simplistic diagram for a solid fuel motor. Ignition is usually a series of pyro explosions. O-Rings separate each section of the engine. Once ignited, conventional solid rocket engines can not be turned off or re-ignited. Solid propellant in the Shuttle SRB’s was a mix of ammonium perchlorate (oxidizer, 69.6% by weight), aluminum (fuel, 16%), iron oxide (a catalyst, 0.4%).
8	Did you know? A very common misconception is that rocket engines need an atmosphere to create thrust/acceleration (forward movement). However, this is not how rocket engines (solid or liquid) operate. Thrust is created using Netwon’s 3^rd law of motion: “When one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body.” In the case of a rocket engine, it’s the expelled, expanding, hot gases exiting from the nozzle at high velocity, that pushes against and opposite the rocket body, that creates the acceleration forces.
9	Orientation and Control Surfaces The three critical flight dynamic parameters are the angles of rotation in three dimensions about the vehicle's center of mass, known as roll, pitch and yaw. While in a gaseous atmosphere, the most common orientation controls comes in the form of control surfaces like control fins, elevators, rudders, ailerons and flaps. Rockets also use complex and sensitive Gyros, gimbaling systems, thrust vectoring (like on the F-22 Raptor built at Lockheed), reactionary control wheels, Reactionary Control Thrusters and other devices for control outside the presence of an atmosphere to operate in the complete vacuum of space.
10	Orientation and Control Surfaces (Cont.)
11	Orientation and Control Surfaces (Cont.) The ISS uses a mix between a GYRO and Reactionary Control Wheels pictured in the last slide called a “Control Moment Gyroscope” (CMG). The main difference between Reactionary Control Wheels and a CMG is that the CMG tilts its spin Axis to induce torque which is far more efficient. Whereas a Reaction Wheel would require megawatts of power to induce the same torque, a CMG can achieve this for only a few hundred watts of power.
12	Power Generation Spacecraft primarily use solar cells or fuel cells to generate electricity Solar cells (also called a photovoltaic cells) use light from the sun converted to electricity by the photovoltaic effect.
13	Power Generation (Cont) Fuel Cells are normally a chemical system as was used on the Apollo program and Space Shuttle program to provide electrical power. The power is generated by the reaction between potassium hydroxide, water, oxygen and hydrogen. These cells are similar to the hybrid electric cars that are available on the market now.
14	Power Generation (Cont) Another type of power generation used on long distance and duration spaceflights like probes and satellites is a “RTG” (Radioisotope thermoelectric generator).
15	What Rover and Probe uses an RTG?
16	Communications There are a number of solutions for Near Earth communications including Laser and Radio wave communications. Recent innovations have made laser communications reliable. LADEE (a probe that was orbiting the moon until 4/18/14) set a record speed of 622mbs from New Mexico to the lunar orbiting craft. Error-free transmission was reliable at 20mbs, faster than most residential homes receive in the U.S.
17	Communications (Cont.) For Deep Space Communications NASA uses both the TDRS satellites as well as Earth based Antennas pictured below for communications with distant spacecraft and rovers. The below picture is a 70m antenna in Goldstone, Cali. This is one of many antennas that communicate with the Voyager probes and the Mar’s spacecraft and Rovers. A common system at Mars is to relay signals from Goldstone and then to MRO/MTO and then its relayed to the Rovers.
18	Life Support Life support, or as NASA refers to it “Enviromental Control”, is a group of devices that allow a human to survive in space. These systems include: food, water, oxygen, carbon dioxide removal, waste management systems and thermal temperature control to name a few. Other systems may include radiation and micro-meteorite protection elements as well. All water is re-used in spaceflight, consider that if you ever want to travel in space. The best defense to radiation is not lead in space, but rather, normal h2o filled walls. Radiation sources are primarily high-energy particles from the Sun.
19	End of Part One Any questions or comments?
20	Spaceflight 101 By: Tyler Waldrop
21	How do you get into Orbit? What exactly is weightlessness and what does it have to do with being in “Orbit”? Lets start by using a thought experiment originally conceived by Newton, which explains both points clearly. Netwon Cannon Example You can think of it as a continual freefall…what actually keeps objects in orbit is that they are going so fast that they keep falling off the edge of the horizon before it can reach it….this happens perpetually.
22	Launch to LEO (Low Earth Orbit) Insertion Following the cannon analogy, lets look at a typical shuttle launch from pad to orbit, to re-enty and finally landing. I will explain each step below :
23	Staging – Why? Why do modern rockets have multiple launch stages that separate instead of just one stage? Answer: To increase the thrust to weight ratio. Thereby increasing the rate of acceleration, and therefore lowering the overall weight and size of the original rocket. If the Apollo-Saturn V rocket did not have all the separate stages, it would have been close to 2 or 3 times as tall and massive and harder to control.
24	Types of Orbits Below are different types of orbits that are used to support a wide variety of applications/mission types ranging from science to surveillance.
25	Orbital Mechanics – Simple Examples – Vocab Terms Prograde Burn – A prograde burn is when you apply thrust in the direction of the forward momentum of the spacecraft and accelerating in relation to the orbiting body. This in return will raise your orbit. Retrograde burn – Same as prograde but the exact opposite by thrusting in reverse of the momentum and decelerating. This is how a spacecraft purposely re-enters Earth’s atmosphere as will be explained shortly. Apoapsis (AP) – The highest altitude of an orbit around another larger gravitational body. Periapsis (PE) – The lowest altitude of an orbit around another larger gravitational body.
26	Orbital Mechanics - Example
27	What goes up, has to eventually come down….mostly! Re-entry is perhaps the most dangerous portion of spaceflight. You re-enter the atmosphere at close to 17,000 mph and travel through super-heated charged plasma as your craft creates friction with atmospheric gases that easily exceed 1200 degrees Fahrenheit. In a planned re-entry, a craft will perform a retrograde burn in the opposite direction of its momentum until its periapsis is low enough to re-enter the Earth’s atmosphere where friction will continue to slow the craft.
28	How does a spacecraft survive re-entry? The most common type of re-entry protection is a thermal protection system (TPS) of some kind, but there is also a new inflatable re-entry system in development. The most common is the “Ablative” type heat shield. It works by creating a protective layer from re-entry friction plasma by burning materials in the heat shield to create a gaseous boundary layer. This is called blockage. Most Ablative heat shields are made mostly from carbon-phenolic which chars, melts and sublimes at high friction within the Atmosphere.
29	Thermal Soak (Tiles) Re-Entry The space shuttles used a system called thermal soak. It consisted of multiple shield types, but the best known is the first use of tiles, which is a trademark of the shuttle program. Without a TPS, the shuttle’s aluminum skin would fail at about 347 °F. The most common tile on the Shuttle’s was High-temperature reusable surface insulation (HRSI) pictured below.
30	Inflatable Heat Shield Technology A new technology being tested and possibly being used on future probes and manned spacecraft will be the inflatable heat shield. The shield is vacuum packed into a diameter of 15 inches.
31	Space Craft Landing Parachutes vs Runway landing – Each have their own benefits: - Parachutes have the upside of being very simplistic and low weight in design and are typically well tested. An issue with parachutes is they can only carry so much weight - A Runway landing, like the space shuttle used, allows for a much safer and controlled final landing phase, but also makes it more complex and requires much heavier systems like the hydraulics and landing equipment
32	Notable U.S. Human Exploration Space Disasters – Apollo 1 In the hasty pace to put a Man on the moon before the Russians, NASA was making too many shortcuts and throwing relative caution to the wind. At 6:30pm on Jan 27, 1967 a fire broke out in the capsule and asphyxiated all 3 crew members during a launch rehearsal while still on the pad. A later investigation determined that a 100% oxygen cabin environment, mixed with faulty wiring and a cabin full of flammable material was at fault. To the left is a picture of the Apollo 1 disaster aftermath.
33	Notable Human Exploration Space Disasters - Challenger The challenger disaster was another case of NASA’s over confidence and impatience in their Shuttle program. The SRB engineers had warned their management they could not guarantee proper O-Ring sealing in these extreme cold temperatures. This was later overturned by SRB management and NASA was given a go to launch anyways. Pad Temperature was 29 °F and was 18°F overnight.
34	Notable U.S. Human Exploration Space Disasters – Columbia Columbia was an unforeseen complication from an overconfident shuttle program once again. During launch, engineers had spotted foam (falling from the external fuel tank insulation) striking the shuttle wing. Management reviewed the launch video and determined the strike was not significant enough to be of concern to the crews safety. NASA was WRONG.
35	Why should we take these risks? Technological Spin-offs: Drug research, fluid dynamics studies, much more efficient power generation and life support systems have had to be designed, which save power, are more efficient and over time much cheaper than current systems on earth. Human inspiration: To remain stagnant, is to admit the utter defeat of all mankind. The Apollo era’s mission to put a man on the moon united all of the Earth, These space programs also inspire the younger generation to pursue science careers that can spin-off to create new discoveries and technologies bettering all mankind. The Gains are worth the Risks!!! For example, next time you use Google Maps on your phone to get somewhere, you can thank our Space Program and the D.O.D. Or, the metal beams in this building we’re in is most likely coated in fire retardant material developed to protect capsules during re-entry.
36	Questions and Comments?