"A Severe Strain on the Credulity"
Of course rockets work in outer space. A rocket engine carries its own fuel and
oxygen so it doesn't need air from the atmosphere to operate.
When the rocket engine fires, it exhausts gases out the nozzle. The combustion of
the fuel forces the gases out the rear of the rocket.
Using Newton's third law we can analyze the forces:
1. Rocket exerts force on gases - they rush out out the nozzle
2. Gases exert force on rocket - it is driven forward.
The effect is similar to the recoil of a cannon which is continuously fired.
In the case of the rocket the loss of gases also reduces the mass and so the acceleration
will increase as fuel is burned.
Small rocket engines or bursts of escaping gas from tanks are used to steer and stabilize
a rocket while in flight. Of course, as expected by the Newton's first law, once
the rocket has reached the desired speed, no further thrust is necessary although
gravity of nearby planets and moons may affect its velocity.
Early in the twentieth century, rocket pioneer Robert Goddard was seeking funding
for development of rockets which would eventually be used to send men and instruments
to the moon. Undaunted by their own misunderstanding of Newton's third law, the New
York times published the following editorial criticizing Goddard and the Smithsonian
for "wasting" their time and money:
As a method of sending a missile to the higher, and even to the highest parts
of the earth's atmospheric envelope, Professor Goddard's rocket is a practicable
and therefore promising device. It is when one considers the multiple-charge rocket
as a traveler to the moon that one begins to doubt ... for after the rocket quits
our air and really starts on its journey, its flight would be neither accelerated
nor maintained by the explosion of the charges it then might have left.
Professor Goddard, with his "chair" in Clark College and countenancing
of the Smithsonian Institution, does not know the relation of action to reaction,
and of the need to have something better than a vacuum against which to react ...
Of course he only seems to lack the knowledge ladled out daily in high schools.
-- New York Times Editorial, 1920
Considering that Goddard's research did lead to perfection of space vehicles
and that Newton's third law applies even in the vacuum of space, this must serve
as one of the best examples for the necessity for nonscientists to understand the
basic principles and laws that govern the physical universe.
