Elements of Astrodynamics

Even if one has the propulsion and power technology to send spacecraft into space this is not enough. To send a spacecraft to the moon one does not just point the rocket at the moon like a rifle pointed at a target. A spacecraft travelling anywhere in the solar system is influenced the gravity field of nearby planets and the sun. Thus the trajectory of a spacecraft is not going to be a straight line. This is most clearly the case for a satellite orbiting the Earth. So for these Newtonian...

Scientific and Technical Requirements

Null Geodesic Black Holes

It is evident that technology of the early 21st century is inadequate for either the relativistic rocket or the starsail. The starsail is closer to current capabilities in principle. Yet this will require spaceflight capabilities and infrastructure far greater than what currently exists. The relativistic rocket does not require massive space infrastructure, but it appeals to exotic physics and engineering that do not exist. In either case the challenges are very daunting. This is a very brief...

The Relativistic Rocket

The most reaching proposed method of propulsion, project Daedalus, can in principle send a spacecraft to at best about 10 the speed of light. It is clear that something more robust is required to explore a star system, particularly if it is more than 10 light years from our solar system. The specific impulse required to reach a significant percentage of the speed of light must be close to the speed of light divided by one-gee. The ideal case would be for s c g 3 x 107 sec. In this case the...

Newtonian Mechanics

Isaac Newton first pondered space flight in a physically correct manner, but with the wrong technology. He illustrated orbital motion by considering a cannon on a high mountain or perch which shot a ball at a high enough velocity to keep missing the curvature of the Earth. Of course he meant this as a method of illustration, yet at the core he demonstrated how a satellite could be put in Earth orbit. By extension Jules Verne in his novel From Earth to Moon, described a trip to the moon in a...

Pab Pa

This then gives an estimated probability of P(A B) 3.08 x 10 4 for any G-class star containing a bio-active planet. This number is likely to represent an approximate upper bound on the probability for the occurrence of Earth-like planets within extrasolar systems based on current data. The perturbing effects due to the higher eccentricities found in extrasolar gas giants has not been included in this analysis. This further indicates nothing about how solar systems are...

L M v

Where e is the eccentricity of the orbit and J is the angular momentum of the orbit. This may be further written as e GM 2a where a yf e2 1) is the semi-major axis. This is an important result in classical mechanics The energy of an elliptical orbit depends upon the semi-major axis. Hence for a planet its energy mass is e -v2 r GM r and the same energy per mass obtains for a spacecraft in this kissing orbit at its semi-major exist e GM 2a2. It it then apparent that the delta-vee required for...

Electromagnetically Accelerated Nanobots

A hot topic in advanced technology in these early days of the 21st century is nanotechnology. While the future trajectory of this technology is very uncertain, it is worth writing a short chapter on the prospect for the use of these as interstellar probes. Nanotechnology is the engineering of systems on the molecular or near molecular scale. These systems are computers with an instruction set encoded on molecules, in a way similar to what nature provides with DNA. These instructions are then...

Special Relativity

In spite of the success of Newton's three laws of motion for two centuries some problems began to arise. These problems were the absence of an aether electromagnetic waves were though to travel on, a precession in the orbit of Mercury not accounted by perturbations from the other planets, and the inability of classical physics to account for the distribution of light frequencies by a non-reflecting hot body, called a black body. The last of these loose threads in the physical world view was...

Eph rmc J l

Below is a table that compares gammas with the fraction Eph mc Equations 8.5 and 8.6 indicate the need to reflect a lot of photons Assume that this sail craft is powered by some solar collector near Earth. If the collector is near Earth there are about 1500 watts m2 of power of solar radiation. For a year as 3 x 107 sec a meter would collect 4.5 x 1010 J. So the mc2 equivalent is about 5 x 10 7 kg. So collecting area is important. To reach a y 2 in one year requires an area of around 1.7 x 106...

R n F

The angle of the radial vector along the lens would be 0 2 r R. which for n 1.5 it is easily found this lens will have a thickness of 60 m. Obviously this is not practical due to the huge mass of such a lens. However, a Fresnel lens will work. The material set into concentric Fresnel zones which act as a slice of the lens at some radius. The sum of these over all concentric zones will concentrate light in the same fashion that a single lens does 8.2 . This technique is used...

The Interstellar Neighborhood

This chapter discusses possible destinations for low gamma spacecraft. There are a number of G-class stars accessible to low gamma spacecraft. These might have terrestrial planets worth exploration. Most of the nearby stars are M-class red dwarf stars. It is unlikely that biologically active planets exist around these stars. However, since they make up the largest number of stars in the galaxy they are still systems worth a close examination, possibly by a starcraft. The stars within 10 light...