| What happened to gravity? Doesn't it operate in | | | | vacuumized tile volume, with a covering of thin |
| space? | | | | glass. The fabrication process - double vacuum, |
| The answer to the above questions is the same | | | | pressurized, is extremely complex. Tile surfaces |
| as for, "Why doesn't the moon fall onto Earth", or | | | | are relatively easily damaged, the inside |
| ".. the Earth into the Sun". Gravity - the attractive | | | | appearance likened to white styrofoam - |
| force between two masses (or bodies - the | | | | however, when the outside temperature is 3000 |
| product of their masses divided by the square of | | | | degrees F, the backside (attached to the |
| the distance between the two centers) - does | | | | aluminum structure of the Orbiter by ordinary |
| act continually and everywhere; the answer, | | | | RTV Room Temperature Vulcanizer) - is only 80 |
| therefore, is that the Shuttle, Space Station and | | | | degrees F. |
| Moon are each traveling at high speeds and | | | | - The highest reentry temperatures are on the |
| (corresponding) heights, circling Earth, as does the | | | | bottom of wing and body, and at the trailing |
| Earth in its orbit around the Sun - and that all are | | | | edges of the control surfaces; there are 30,000 |
| always "falling around" the curvature, e.g. of the | | | | black tiles; NASA has reported the cost at $2500 |
| Earth. Although the flight path of the orbiting | | | | each. |
| vehicle (or moon, or planet) attempts to be a | | | | However, because of the tremendous insulating |
| "straight" line - it is continually being pulled down by | | | | capability of the tiles, a greatly simplified and |
| gravity - so that as "satellites" they continually | | | | reliable Space Shuttle concept has been |
| travel in stable orbits, circular or elliptical. The | | | | achievable: |
| same is true throughout the universe, and while | | | | - The Orbiter vehicle itself was essentially |
| attractive forces exist between all bodies in the | | | | designed and constructed much as a conventional |
| Universe, each to each other, the factor of | | | | aircraft - its only flight function, landing after |
| distance-squared in the denominator effectively | | | | reentry, uses conventional flight controls, tires and |
| eliminates the significance of all other bodies in | | | | brakes (the landing speed is similar to a |
| comparison to the two involved in satellite orbiting. | | | | commercial jet aircraft, about 160 mph). |
| To put a numerical perspective upon what has | | | | - There is no propulsive capability for orbiting or |
| become a casual acceptance of space activities, | | | | landing, the speed and momentum of the vehicle |
| to achieve a stable orbit, the Shuttle Orbiter | | | | after reentry, permitting the astronaut-pilot to |
| vehicle - which does not have propulsive power | | | | maneuver the craft into the pre-selected NASA |
| while orbiting - must rise to a sufficient height | | | | airport and runway for landing. |
| above the Earth's air layer, where the vacuum of | | | | - The most powerful and efficient rocketry |
| space produces no "drag" resistance (generally | | | | arrangement is therefore designed for the lift-off |
| about 125 miles altitude) - to achieve this, the | | | | sequence: two solid rockets (approximately |
| lift-off propulsion system must propel the orbiting | | | | twelve feet in diameter), plus the three Orbiter |
| vehicle to approximately 18,000 miles per hour | | | | engines (fueled by the large center fuel-oxidizer |
| (note: traveling in the easterly direction gains the | | | | tank); all five are fired simultaneously for |
| Earth-surface rotational speed of about 1000 | | | | maximum thrust at lift-off (approximately seven |
| mph). | | | | million pounds thrust required) - along with the |
| At the completion of the mission, to return to | | | | giant ground-retention explosive bolts at the base |
| Earth, the Orbiter is slowed slightly - dropping | | | | of the solid rockets (only attachment of the |
| closer to Earth - smashing into individual air | | | | entire assemblage to the launch platform). |
| molecules, which are "vaporized" by the impact - | | | | - After twelve minutes of flight, the exhausted |
| a tiny pulse of both "drag" (causing further slowing | | | | solid rockets are depleted and dropped |
| and lowering of the Shuttle) and also of "heat". As | | | | (parachuted and recovered in the ocean); the |
| the Shuttle is slowed and lowered for the reentry | | | | three on-board engines continue until the center |
| mode, the heat build-up develops tremendous | | | | tank is empty, when it is separated; afterwards, |
| temperatures of up to 3000 degrees Fahrenheit - | | | | the Orbiter, traveling at orbiting altitude and speed, |
| requiring the insulating "tiles", which cover the | | | | has no more propulsive capability. |
| lower wing and body surfaces. | | | | A human-interest worry about mankind's 21st |
| The concept of the Space Shuttle is remarkably | | | | century "Space adventures" is space debris - the |
| and functionally (and beautifully) simple and reliable | | | | remains of space-hardware rocketry that have |
| - as a result of reliance upon this function of | | | | not, as yet, returned to Earth. Varying in size |
| insulation - in an absolutely hostile, unforgiving | | | | from complete rocket stages to tiny particles, |
| space environment of cryogenic iciness plus | | | | they are true hazards because of their thousands |
| vacuum. The rentry insulation tiles, invented and | | | | of mph travel speeds. The larger ones are |
| developed by NASA and Lockheed Aircraft, shield | | | | monitored - just recently, March 5, 2009, |
| the Orbiter Spacecraft (fabricated of conventional | | | | warnings about a possible strike of the |
| light, aluminum-alloy thin skin-stringer construction, | | | | International Space Station forced the US |
| similar to most sub-sonic aircraft of that era) | | | | astronauts to take shelter in the parked Russian |
| from re-entry heat - temperatures which would | | | | Soyuz capsule. Two months ago, two satellites |
| melt the strongest alloy steel. | | | | collided in orbit, adding several hundred new pieces |
| - The tiles are individually designed for the | | | | of "junk" to the space debris litter-belt circling |
| anticipated reentry temperatures, 6x6 inches in | | | | Earth. The NASA Orbital Debris Program Office is |
| size and average about 1 inch in depth; | | | | at Johnson Space Center, reporting that about |
| - Inside, they are comprised of extremely long, | | | | 13,000 such threats are constantly tracked, of |
| fine filaments of quartz, compressed into the | | | | about 600,000 total debris items. |