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Journey to The Planets

The Technology to Build a Spacefaring Civilization

Author: Giancarlo Genta

Publisher: Springer Nature Switzerland

Book Series : Space Technology Library

Part of: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

Table of Contents

About this book

This book gives an account, as little biased as possible, on human space missions beyond low Earth orbit in general, and specifically to the planets of the solar system. The importance of advanced propulsion is stressed and the mathematical methods needed to design missions based on them are described. The included computer code allows the user to assess the feasibility of the various missions using different propulsion systems and how advancements in propulsion can allow humankind to become a true spacefaring civilization.

As opposite to the majority of books dealing with mission design, where the subject is usually dealt with in a highly mathematical way, here an attempt is made to avoid as much as possible the mathematical complexities and to focus on the practical aspects of the design. However, the equations needed to make numerical analysis and simulations of the missions are described and discussed.

An original computer code is included in the book, and an appendix helps the reader to understand how to use it. The code is different from existing ones since its main aim is to be user friendly and to allow the user to make a preliminary design of interplanetary missions aimed to planets and their satellites, comets or asteroids.

Frontmatter

1. Introduction: Building a Spacefaring Civilization

Abstract

We are living in what was dubbed the ’space age’, a term coined at the end of the 1950s, when the first artificial satellite was launched. Today going to space, although mostly only to Earth orbit, at least with automatic machines, is not only necessary for providing essential services and for performing science, but it is an activity whose economical importance is growing.

Giancarlo Genta

2. The Solar System

Abstract

The motion of the planets of the solar system is complex but, if their mutual gravitational attraction is neglected and their orbits are assumed to be governed only by the attraction of the Sun, they would move along elliptical orbits.

Giancarlo Genta

3. Propulsion for Interplanetary Journeys

Abstract

Almost all spacecraft at present use propellant to produce a thrust to implement any change of velocity and the only propellantless propulsion envisaged is light or magnetic sails. Since the mass of the propellant which is carried on board is a large fraction of the initial mass to be carried in low Earth orbit (IMLEO) of any spacecraft and thus constitutes a large fraction of the cost of space missions.

Giancarlo Genta

4. Point-to-Point Motion in Field-Free Space

Abstract

The study of point to point motion in a field free space is quite interesting for several reasons. It supplies a very simple case which can be solved in closed form, allowing to understand the possible control strategies and, at the same time, in some cases can be used as a first approximation for interplanetary travel. It will be here studied in some detail.

Giancarlo Genta

5. Leaving Earth

Abstract

At our present level of technology, all interplanetary journeys must start from the Earth surface, i.e. deep into the gravitational well of Earth, and are also concluded on the surface of Earth. Exiting from this gravitational well is one of the most difficult and costly phases of all interplanetary missions. A similar situation occurs in the return journey, which must start from the surface of the destination planet. Also the opposite maneuver, a safe entry, descent and landing on the destination planet, is difficult even if, in the case of planets with an atmosphere, aerodynamic forces may be of help in reducing the cost of this phase of the journey. The final phase, re-entry into the Earth atmosphere, is also a difficult, and even dangerous, maneuver.

Giancarlo Genta

6. Interplanetary Travel: Impulsive Approximation

Abstract

Chemical rockets, and also nuclear thermal rockets, supply large thrusts for a short time: the simplest way to compute the trajectories which can be obtained using this type of propulsion is the so-called “patched conics approximation”, in which propulsive phases, reduced to instant changes of velocity, are alternated to phases in which the spacecraft proceeds under the effect of the gravitational attraction of the solar system bodies. Assuming that only one celestial body acts at a time, these coasting arches are conic sections. Idealized solutions obtained by assuming that planetary orbits are circular and coplanar, are first described; while more realistic solutions in which the departure and arrival planets follow elliptical and non-coplanar orbits, are then considered.

Giancarlo Genta

7. Interplanetary Travel: Continuous Thrust

Abstract

Electric propulsion is characterized by values of the specific impulse much higher than those typical of thermal (chemical or nuclear) rockets but produces much lower thrusts. This is obviated by using the thruster for long periods of time or even for the whole travel. The design of the trajectory must be thus integrated with that of the thrust profile and it is possible to obtain very good performance in this way, at the cost of much larger design complexity.

Giancarlo Genta

8. Orbit to Orbit Travel: Continuous Thrust

Abstract

The optimization of the spacecraft cannot however be performed considering only the interplanetary leg of the space travel: the optimization must take into account the whole journey, which is made by at least 3 phases: the acceleration around the starting planet, the interplanetary transfer and the braking around the destination planet. A low thrust spacecraft may start from a low orbit about the starting planet using its own thrusters, performing a spiral trajectory leading it outside the sphere of influence of the planet, or may use a booster to perform a quick escape from the starting orbit. The same can be done at arrival, with the added possibility of performing an aerodynamic maneuver,

Giancarlo Genta

9. Trajectories in the Earth-Moon System

Abstract

The Moon is the closest celestial body and the easiest to reach. Traveling to the Moon is relatively easy even with present technology, as it is evidenced by the very fact that half a century ago the Apollo Missions carried 12 people on our satellite. Taking into account the advances in technology in general (non only space technology), today reaching the Moon is much easier and above all much less costly. However, the analysis of the missions in the Earth-Moon system is much more difficult than that of interplanetary missions, since the errors introduced by the restricted two-body problem are much larger and to obtain a good precision the restricted three body problem must be solved. To this a consideration must be added: low thrust propulsion, such as NEP or SEP (and even solar sails) may be expedient to decrease the cost of lunar missions, but imply an increase of the travel time except if very advanced power generators are used. With technologies predictable for the near or medium term future, low-thrust may be used only for slow cargo spacecraft but not to carry human beings to the Moon and back.

Giancarlo Genta

10. Travelling Between Extrasolar Planets

Abstract

If in the future humans will reach other stars, or better extrasolar planets, they will face the problem of travelling between the new planets. Many planetary systems are much more complex than the solar system, particularly in case their star is double or multiple, and there is a variety of possible cases. In most cases the restricted two body assumption cannot be used and even in case of impulsive propulsion the trajectories cannot be obtained in closed form. The problem of finding the impulsive trajectory can be reduced to the solution of a boundary value problem, as is the case for continuous thrust solved through indirect methods. A few examples for an hypothetical extrasolar system are dealt with, with the only aim of discussing possible way to tackle the problem of traveling between exoplanets.

Giancarlo Genta

11. Conclusions

Abstract

After a hiatus of almost half a century, humankind is about to restart its way beyond low Earth orbit to return to the Moon on our way to the exploration and the colonization of the Solar System. To become a true spacefaring civilization we must acquire a new know-how in many fields of technology, but we do not need revolutionary advances in science or technological breakthroughs.

Giancarlo Genta

Backmatter

Title: Journey to The Planets
Author: Giancarlo Genta
Publisher: Springer Nature Switzerland
Electronic ISBN: 978-3-031-57696-6
Print ISBN: 978-3-031-57695-9
DOI: https://doi.org/10.1007/978-3-031-57696-6