Space Systems Engineeringand Design

Christopher D. HallAerospace and Ocean Engineering

Virginia Tech, 1997Our journeys to the stars will be made on spaceships created by determined, hardworking scientists and engineers applying the principles of science, not aboard flying saucers piloted by little gray aliens from some other dimension.

— Robert A. Baker in “The Aliens Among Us: Hypnotic Regression Revisited”, The Skeptical Inquirer, Vol. XII, No. 2, 1988

Thoughts on Space

Some comments overhead at the Officer’s Club• It’s a really big place with no air.

• There’s nothing out there, is there?

• How many g’s is that satellite pulling

when the ground track makes those turns?

• Why can’t I have my spy satellite

permanently positioned over Moscow?

Just How Big Is It?Light Time Approximate Distance Example

1 second 299,792 km ~0.75 Earth-Moon distance

1 minute 18,000,000 km 0.125 AU

8.3 minutes 150,000,000 km Earth-Sun distance (1 AU)

1 hour 1,000,000,000 km ~1.5 Sun-Jupiter Distance

4 years (Included for reference) Distance to nearest star

Interestingly, according to modern astronomers, space is finite. This is a very comforting

thought — particularly for people who can never remember where they have left things.

— Woody Allen

Relative Sizes of Planetary Orbits

I was in a job interview and I opened a book and started reading. Then I said to the guy, "Let me ask you a question. If you are in a spaceship that is traveling at the speed of light, and you turn on the headlights, does anything happen?" He said, "I don't know." I said,

"I don't want your job." — Steven Wright

Just How Much Nothing Is Out There?• Space has 3 kinds of “nothing”

– No gravity (well, not really)– No air (well, not really)– Nothing to block your view (well, not really)

• And a few something’s out there, too

Outer space is no place for a person of breeding. — Lady Violet Bonham Carter

WeightlessnessThis illustration from Jules Vernes Round the Moon shows the effects of “weightlessness” on the passengers of The Gun Clubs “bullet” capsule that was fired from a large gun in Florida.

No Gravity?• Newton’s Universal Gravitation Law

G = 6.67310-20 0.001 10-20 km3/(kg s2)

M = 5.973320 1024 kg

r ranges from 6378+200 km (LEO) to 42,164 km

R + altitude

Acceleration due to gravity is: ag = Fg/m

2r

GMmFg

M

mr

Gravitational AccelerationThis plot shows

how gravitationalaccelerationfalls off as altitude increases.Notice that theacceleration at LEO is about 90% of that at the surfaceof the Earth. Space isn't remote at all. It's only an hour's drive away if

your car could go straight upwards. — Fred Hoyle

Microgravity• Weightlessness, free fall, or zero-g

• Particles don’t settle out of solution, bubbles don’t rise, convection doesn’t occur

• Microgravity effects in LEO can be reduced to 10-1 g (1 g)

On Earth, gravity-driven buoyant convection causes a candle flame to be teardrop-shaped (a) and carries soot to the flame's tip, making it yellow. In microgravity, where convective flows are absent, the flame is spherical, soot-free, and blue (b).

No Air Out There?

Better not take a dog on the space shuttle, because if he sticks his head out

when you're coming home his face might burn up. — Jack Handey

The atmosphere doesnt just abruptly end. There really is air and lift and drag in space.• Must be overcome during launch

• Used to reduce velocity during reentry

• Used for “aerobraking” maneuvers

• May someday be used for other “aeroassisted” maneuvers

Whats There to Block Your View?The fraction of the Earth you can see at any instant is substantially

larger than any Earth-based or aviation-based instruments.

A friend of mine once sent me a post card with a picture of the entire planet Earth taken from space. On the back it said, “Wish you were

here.” — Steven Wright

• Fred Hoyle:

• "Space isn't remote at all. It's only an hour's drive away if your car could go straight upwards."

• Vice President Dan Quayle, 9/5/90:

• "For NASA, space is still a high priority."

• Lady Violet Bonham Carter:

• "Outer space is no place for a person of breeding."

• Woody Allen:

• "Interestingly, according to modern astronomers, space is finite. This is a very comforting thought-- particularly for people who can never remember where they have left

• things."

• Marshall McLuhan:

• "There are no passengers on spaceship earth. We are all crew."

• Michael Collins Former astronaut and past Director of the National Air and Space Museum:

• "Our journey toward the stars has progressed swiftly. In 1926 Robert H. Goddard launched the first liquid-propelled rocket, achieving an altitude of 41 feet. In 1962 John Glenn orbited the earth. In 1969, only 66 years after Orville Wright flew two feet off the ground for 12 seconds, Neil Armstrong, Buzz Aldrin and I rocketed to the moon in Apollo 11."

• Robert A. Baker, "The Aliens Among Us: Hypnotic Regression Revisited", The Skeptical Inquirer, Vol. XII, No. 2:

• "Our journeys to the stars will be made on spaceships created by determined, hardworking scientists and engineers applying the principles of science, not aboard flying saucers piloted by little gray aliens from some other dimension."

• William Shatner as Kirk, in "Star Trek IV:The Voyage:

• "I'm from Iowa, I only work in space."

• Wernher von Braun:

• "Man is the best computer we can put aboard a spacecraft... and the only one that can be mass produced with unskilled labor."

• Steven Wright:

• A friend of mine once sent me a post card with a picture of the entire planet Earth taken from space. On the back it said, "Wish you were here."

• Jack Handey:

• Better not take a dog on the space shuttle, because if he sticks his head out when you're coming home his face might burn up.

• Steven Wright:

• I was in a job interview and I opened a book and started reading. Then I said to the guy, "Let me ask you a question. If you are in a spaceship that is traveling at the speed of light, and you turn on the headlights, does anything happen?" He said, "I don't know." I said, "I don't want your job."

“Scientifiction” Provides Motivation

This is the first issue of the first science fiction “pulp” magazine published in November 1928.The lander appears to be on one of Jupiters 16 moons.This years senior designproject is to design a landerfor a mission to Europa, whichprobably has no palm trees!

Hubble Space Telescope

Some Recent NASA Spacecraft