Orbital Loop Mac OS

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ORBITAL LOOP

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An endless tether is launched in an eccentric Earth orbit. It isinterspersed with winches and a segmented tube. A sounding rocketor a gun carries cargo to the tube. When the cargo enters the tube,it is accelerated by friction to the orbital velocity. Half of theorbital energy of the loop is transferred to the cargo, while theother half is wasted as heat. The orbital loop is durable butsomewhat unstable. The minimum mass of a steel loop is 1000tons.

Cargo is enclosed in a ball-shaped container. A thick coating ofsilicon rubber (e.g., Dow Corning 3-6077 RTV) protects thecontainer from heat and vibration. Gas produced by ablation of therubber generates friction which transfers the orbital energy to thecargo. The tube is tapered to compensate for the ablation. When thecontainer has attained orbital velocity, it drops off, and iscarried to its final destination by a variety of economical,low-thrust propulsion techniques.

As the loop follows the eccentric orbit, its velocity andtension undergo periodic changes, not unlike those of a pendulum ora swing. These periodic changes make it possible to restore theloop's energy without the use of propellants or electrodynamictethers. Winches exert a periodic force on the loop which issynchronized with the orbital movement of the loop. Much like achild 'pumping' a playground swing, the periodic force replenishesthe energy of the loop.

BIBLIOGRAPHY

Andrew Nowicki, 'Diversity,' TheTrumpeter, Vol. 10, No. 2, Spring 1993, pp. 65-68.

DETAILS

Orbital loop

Cargo approaching the tube (large image 47k)

Electromagnets can transfer momentumto the cargo with a greater efficiency than the tube, but they aremassive and require more maintenance.

The gravity of the oblate Earth perturbs the loop. Theperturbation results in a precession of the orbital plane, whichmeans that the orbital plane rotates about the axis of Earthrotation. The period of precession is on the order of severalmonths. [ref. 1]

The dynamic behavior of the orbital loop is so complex that itcan be analyzed by computer simulation only. The winches canstabilize the loop [ref. 2-5], but wings interacting with theionosphere may be more efficient.

The optimum orbit of the loop corresponds with the greatest'lineal power,' which is defined as the power generated by the loopper lineal meter of the loop, per tensile strength of its tethers.If no energy is spent on maintaining the dynamic stability of theloop, its lineal power is:
p = (V1 -V2)/(V1 T)
where:
P is lineal power (power per lineal meter per tensilestrength)
V1 is maximum velocity
V2 is minimum velocity
T is orbital period = 2(PI)(A3/K)0.5[ref. 6]
K is gravitational constant times mass of the Earth = 4.0E14m3s-2
A is semi-major axis

Length of the loop (i.e. Total length of its tethers) is: L =V1 T

Velocity at a given point along the elliptic orbit is:
V = (K(2/R-1/A))0.5 [ref. 7]

R is defined as the distance between center of the Earth and agiven point along the orbit. Assuming that the perigee of the loopis 200 kilometers above the Earth's surface, the minimum value of Ris R1 = 6,580,000 meters and the maximum velocity is:V1 = (K(2/R1 -1/A))0.5

At the apogee: R = R2 = A+E
where:
E = eccentricity =(A2-B2)0.5
B = semi-minor axis

The loop will collide with the Earth unless the radius of itsorbit at the perigee is at least R1.
B = (R1 A)0.5, V2 =(K(2/(A+(A2-R1A)0.5)-1/A))0.5
The results are summarized in the following chart.

Optimum orbit of the loop

Assuming that the loop has steel tethers, that the maximumtension is 2 GPa, and that half the power is spent on maintainingdynamic stability, the loop can bring its mass to a low Earth orbitin about 6 months. If the loop is integrated into a Moon-Earth momentum exchange, it can bring itsmass to a low Earth orbit in 2 weeks.

The most vulnerable parts of the loop are tethers. Damage causedby meteoroids, man-made debris, and oxygen determines the minimummass of the loop. If adjacent winches are linked by severaltethers, the loop can remain operational even if some tethers arebroken. In order to reduce damage, tethers should present a largesurface area to meteoroids which approach from all directions.

An arcuous tether shown below is lightweight, has a largesurface area, and can be flattened when it is wound up inside thewinch. Suppose that the loop is composed of N = 10,000 segments,each segment consisting of two parallel, 2 centimeter wide tethersattached to the winches on each end. The distance between adjacentwinches oscillates between 3.2 and 7.0 kilometers, so the averagetether area exposed to meteoroids is (5.1 km)(2 cm) = 102m2. There is an X = 0.5 probability that a given tetherwill be broken by meteoroids or debris in 25 years. [ref. 8] If thetether is broken, the loop must be relaxed to avoid breaking theother tether of the same segment. After the loop has been relaxed,winches slowly pull the operational tether of the damaged segment.Finally, the adjacent winches are joined, thereby eliminating thedamaged segment of the loop. If both tethers of the same segmentare broken, the loop ruptures, and is unable to carry cargo untilit is repaired. Suppose that it takes 4 hours to bring the adjacentwinches together after one tether breaks. The probability that theremaining tether breaks during the 4 hour period is Y =X/((25)(365)(6)(2)) = 5E-7. The probability that the loop rupturesin 25 years is Z = 1-(1-XY)N = 0.003.

Arcuous tether

The tube that accelerates the cargo is about 200 km long. It istapered to compensate for the ablated rubber. The tube cannotoverheat because the mass of the cargo is 2 orders of magnitudesmaller than the mass of the tube. A metal tube is economical, butit may be damaged if the cargo travels faster than 5 km/s (speed of sound in the tube).If the metal tube is used, the cargo must be accelerated to 4 km/s,before it enters the tube. A glasstube reinforced with high modulus graphite fibers is expensiveand difficult to assemble in space, but it has the speed of soundof about 10 km/s.

As the tube follows its elliptic orbit, it is subjected toalternating tensile and compressive forces. The compressive forceis the greatest when the loop ruptures. To reduce the forces, thetube is divided into loosely fitting telescoping segments. If thecargo container is in jeopardy, the tube segments ahead of thecontainer are moved aside, thereby letting the container out.

Shortly before the cargo is fired from the gun, the altitude ofthe tube is reduced to the maximum range of the gun. The loopundulates and changes its tension in order to move its tube intothe path of the unguided gun projectile. Vertical undulationcompromises stability, so the loop must undulate horizontally.

Orbital Loop Mac Os Download

Undulating loop (largeimage 30k)

A similar contraption named the electrotube is constantly immersed in theionosphere, so it experiences a much greater aerodynamic drag andoxygen erosion. A rocket must guide cargo all the way from theEarth to the electrotube. Despite these inconveniences, theelectrotube is an attractive precursor of the loop, because itsminimum mass is only 100 tons.

A loop orbiting the Moon can carry its mass to a low orbit 17times faster than a similar loop orbiting the Earth. Low gravityand the absence of atmosphere make it easy to transport containersfrom the Moon to the perigee of the loop. The same loop canaccelerate containers bound for space and slow down containersbound for the Moon.

According to the chart the loop must be highly eccentric togenerate the maximum power and carry the maximum tonnage of cargo.The vibration and precession of the loop make it difficult to usemore than one independent, eccentric loop in the Earth orbit.Independent loops could either collide or force each other tooperate at a reduced capacity. It seems that the best solution tothis dilemma is the construction of a multitude of parallel loopsattached to each other. If one loop ruptures, it can still workbecause of the structural support of the adjacent loops.

The orbital loop can launch satellites, stabilize them, and keepthem in correct orbit. Satellites attached to the loop do notgenerate much drag, so the loop does not have to generate muchpower and does not have to be very eccentric. Several nearlycircular satellite loops can coexist in equatorial orbits, withroom to spare for one inclined, eccentric, Sun-synchronous looptransporting cargo to space.

REFERENCES

  1. Krafft A. Ehricke, Space Flight, Vol. II -- Dynamics,Van Nostrand, Princeton, 1962 p. 168.
  2. J. V. Breakwell, 'Stability of an Orbiting Ring,' presented atAIAA 18th Aerospace Sciences Meeting, Pasadena, CA, Jan14-16, 1980, AIAA-80-0057.
  3. A. M. Fridman, A. I. Morozow, and V. L. Polyachenko, 'TheDestruction of a Continuous Ring Revolving Around a GravitatingCenter,' Astrophysics and Space Science, Vol. 103, 1984, pp.137-142.
  4. Vladimir Vasilievich Beletskii and Evgenii M. Levin, 'Dynamicsof Space Tether Systems,' Advances in the AstronauticalSciences Vol. 83, Univelt 1993, pp. 465-483.
  5. Vladimir Vasilievich Beletskii and Evgenii M. Levin, 'Stabilityof a Ring of Connected Satellites,' Acta Astronautica, Vol.12, 1985, pp. 765-769.
  6. Krafft A. Ehricke, Space Flight, Vol. I -- Environment andCelestial Mechanics, Van Nostrand, Princeton, 1960, p.266.
  7. Ibid. p. 277.
  8. William. A. Bacarat and C. L. Butner, Tethers inSpace Handbook, NASA, 1986, page 4-32.
Curator: Al Globus
If you find any errors on this page contact Al Globus.

Orbital Loop Mac Os Catalina

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Bandmateloops.com on Thursday announced the release of Low Orbital Beats, a new collection of drum loops for GarageBand musicians. Low Orbital Beats is available for online purchase and download for US$19.95. The loops also work with Logic 7 and Soundtrack.

Low Orbital Beats was produced by Peace Love Productions and features what the publisher describes as “funky downtempo/chill-out rhythms with a little moon dust sprinkled in for good measure. It’s billed as a cross-genre rock and hip-hop collection with a distinctly electronic theme. One-hundred fifty seven drum loops and effects are included in the collection, which totals 147MB.

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Preview loops and a song demo are available for review from the Bandmateloops.com Web site.