Kronos: Devourer Of Worlds


Lorenzo von Matterhorn
Jan 31, 2009
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Kronos: Devourer Of Worlds


Kronos: Ravager of Planets (1957)



Mentioned in the video above about a previous topic covered by their channel - the outward moving solar system habitable zone as the sun ages. A fix: very gradually move the orbit of the Earth outward with an asteroid moved to an orbit which passes Jupiter and Earth, something I found much more interesting than the topic of Kronos: Devourer Of Worlds.

Talk about thinking ahead...:



The Sun’s gradual brightening will seriously compromise the Earth’s biosphere within ~ 10^9 years. If Earth’s orbit migrates outward, however, the biosphere could remain intact over the entire main-sequence lifetime of the Sun. In this paper, we explore the feasibility of engineering such a migration over a long time period. The basic mechanism uses gravitational assists to (in effect) transfer orbital energy from Jupiter to the Earth, and thereby enlarges the orbital radius of Earth. This transfer is accomplished by a suitable intermediate body, either a Kuiper Belt object or a main belt asteroid. The object first encounters Earth during an inward pass on its initial highly elliptical orbit of large (~ 300 AU) semimajor axis. The encounter transfers energy from the object to the Earth in standard gravity-assist fashion by passing close to the leading limb of the planet. The resulting outbound trajectory of the object must cross the orbit of Jupiter; with proper timing, the outbound object encounters Jupiter and picks up the energy it lost to Earth. With small corrections to the trajectory, or additional planetary encounters (e.g., with Saturn), the object can repeat this process over many encounters. To maintain its present flux of solar energy, the Earth must experience roughly one encounter every 6000 years (for an object mass of 10^22 g = 10^19 kg). We develop the details of this scheme and discuss its ramifications.

Discussion (exerpts)

In this paper, we have investigated the feasibility of gradually moving the Earth to a larger orbital radius in order to escape from the increasing radiative flux from the Sun. Our initial analysis shows that the general problem of long-term planetary engineering is almost alarmingly feasible using technologies that are currently under serious discussion. The eventual implementation of such a program, which is moderately beyond current technical capabilities, would profoundly extend the time over which our biosphere remains viable.

An important aspect of this scheme is that a single Kuiper Belt object or asteroid can be employed for successive encounters. In order to move the Earth at the required rate, approximately one encounter every 6000 years (on average) is needed (using objects with mass ~ 10^22 gm). Due to the acceleration of the Sun’s luminosity increase, the encounters must be more frequent as the Sun approaches the end of its main-sequence life. In order to use the same secondary body for many encounters, modest adjustments in its orbit are necessary. However, by scheduling the secondary body to encounter additional planets (e.g., Jupiter and/or Saturn) in addition to the primary Earth encounter, the energy requirements for orbital adjustment at the object’s aphelion can be substantially reduced. In particular, the energy consumed by such course corrections is not likely to dominate the energy budget.

Potentially more serious questions involve the rotation rate of the Earth and the Moon’s orbit. We expect that O will raise a tide in the Earth during its encounter. The tide could be substantial; although O would be a relatively small body, the
closeness of its passage means that the transient forcing potential would be O(10) × as strong as that of Moon, for a 10^22 gm body passing 109 cm from the Earth’s center. Calculating the size and phase of the tide would require detailed work, but qualitatively we would expect any tidal bulge to lag in phase behind O, as O moves
more quickly than the Earth rotates. This in turn implies a spin-up of the Earth (similar resoning accounts for the spin-down of the Earth by the Moon). Given the very large number of encounters planned, a serious increase in the Earth’s rotation rate could result.

However, the above picture, leading to spin-up, takes place only for ‘incoming’ encounters, such as depicted in Figures 1 and 2. The symmetry of the encounters equally allows ‘outgoing’ encounters, in which O passes by the Earth after its
perihelion. Such encounters also pass by the Earth’s leading limb from inside the Earth’s orbit. They are thus retrograde with respect to the Earth’s rotation, and the same considerations as above now lead to spin-down of the Earth rather than spinup. Thus, by careful planning of encounters, we can cancel any unbalanced torques exerted on the Earth.

As for the Moon, reasoning by analogy with cases of stellar binaries and thirdbody encounters suggests that the Moon will tend to become unbound by encounters in which O passes inside the Moon’s orbit. (As well, there is the non-zero probability of collisions between O and the Moon, which must be avoided.) Again, detailed quantitative work needs to be done, but it seems that the Moon will be lost from Earth orbit during this process. On the other hand, a subset of encounters could be targeted to ‘herd’ the Moon along with the Earth should that prove necessary. It has been suggested (cf. Ward and Brownlee 2000) that the presence of the Moon maintains the Earth’s obliquity in a relatively narrow band about its present value and is thus necessary to preserve the Earth’s habitability. Given that the Moon’s mass is 1/81 that of the Earth, a similarly small increment of the number of encounters should be sufficient to keep it in the Earth’s environment.

The fate of Mars in this scenario remains unresolved. By the time this migration question becomes urgent, Mars (and perhaps other bodies in the solar system) may have been altered for habitability, or at least become valuable as natural resources. Certainly, the dynamical consequences of significantly re-arranging the Solar System must be evaluated. For example, recent work by Innanen et al. (1998) has shown that if the Earth were removed from the Solar System, then Venus and Mercury would be destabilized within a relatively short time. In addition, the Earth will traverse various secular and mean-motion resonances with the other planets as it moves gradually outward. A larger flux of encounters might be needed to rapidly escort the Earth through these potential trouble spots. In this case, additional solar system objects may require their own migration schemes. Alternately, this technology could be used, in principle, to move other planets and/or moons into more favorable locations within the solar system, perhaps even into habitable zones. As another application, the basic mechanics of this migration scheme could be employed to clear hazardous asteroids from near-Earth space.

and, finally, LOL!:

An obvious drawback to this proposed scheme is that it is extremely risky and hence sufficient safeguards must be implemented. The collision of a 100-km diameter object with the Earth at cosmic velocity would sterilize the biosphere most effectively, at least to the level of bacteria. This danger cannot be overemphasized.

Rex R

Apr 21, 2010
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Larry Niven wrote a story that used this idea. 'a world out of time'.


Sep 12, 2013
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SE Wisconsin
You beat me to it, Rex. An asteroid would be easier to use as the driving mass than Uranus, like in the Niven story.

Sent from my iPhone using Rocketry Forum


Well-Known Member
Jul 1, 2011
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Uranus .

Futurama clip:


HV Arcas, AT F67
Aug 15, 2017
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Framingham, MA
All well and good, but how many of you also know that in the "B" sci fi film, was George O'Hanlon (dude with the glasses in the second frame) aka the voice of George Jetson? :)