Evidence of the last 60 or so years
to the contrary, three-stage rockets are not the only
way to launch payloads into space.
Wernher von Braun was the supreme
advocate of the brute force approach to space travel:
namely, bigger is better. If you needed more payload
weight, add another stage or a couple more engines to
the first stage. He didn't have time or room in his
universe for different approaches. He did, however, sit
up and take notice when he was shown a film of a model
for a nuclear pulse propulsion design that was in a very
early stage of development, but it never was developed
to even the test phase.
Eventually, of course, we did go to
the moon, and we did do it his way, sort of. A rather
obscure NASA engineer, over a weekend, came up with the
concept of taking to the moon's surface only what was
necessary (the Lunar Excursion Module) and leaving the
rest (Command Service Module) in orbit around the Moon.
That saved enough launch weight to make the von Braun
concept work, namely the Saturn 5, and the rest is
A casualty of the Apollo concept
was the iconic 1950ís needle-shaped rocket sitting on
its tail on the Moonís surface, a sight made famous in
the film Destination Moon and many book and
magazine illustrations of the period, as well as many
The difficulty of landing the spaceship is
usually glossed over in the movies. An actual landing,
with the pilot lying on his back and using a radar
altimeter and a TV camera to land the ship on its tail
would be impossible for any pilot, even in the one-sixth
gravity found on the Moon. Today it is achievable using
variable-thrust rocket engines and computer control.
Possible, but not easy. Just ask the people at Space-X,
who land their booster rockets that way. More realistic
is a compact lunar lander, resembling a helicopter
rather than a rocket, with the pilot sitting upright (or
standing) and the center of thrust and the center of
gravity mush closer together than is possible with the
traditional rocket design.
After Apollo, we had the Space
Shuttle - the ultimate development of 1950's rocket
technology. Propelled by liquid hydrogen/oxygen, with
higher rocket chamber pressure than Apollo and
discardable (but reusable) solid-fuel boosters, the
Space Shuttle could launch reasonable payloads into
low-earth orbit, and it was reusable. It worked well
enough to be the workhorse of the American space program
for thirty years.
But there must be other ways, maybe
even better ways, to achieve the same goal.
Just watching an Apollo moon launch
shows you the fallacy of the brute force approach. The
initial velocity of the spacecraft is zero. It is
literally balanced on a column of exhaust gases. Could
there be a better way?
With the end of the Space Shuttle
era and the entry of private space companies such as
Space-X supplying the International Space Station,
newer, more innovative technologies are emerging that
were neglected until recently. Private space companies
are taking these more radical ideas and making them
Let's look at some of those radical
Most alternative configurations
involve replacing the first stage of a three-stage
rocket with something else: an airplane, a rocket sled,
or a rail gun.
The first possibility is an
airborne, jet-powered, reusable first stage, such as an
airplane, carrying the second stage.
The airplane takes off, flies to
its maximum altitude and speed and releases the
spaceship to continue its journey into space. Think
Spaceship 1. This concept is currently being implemented
by several private space companies, including Virgin
Galactic, which is using a Boeing 747 to provide initial
The rocket sled is another
alternate approach. It is capable of launching a
spacecraft without ever leaving the ground. The concept
originated in the late 1930's and became popular in the
1950's. It has several apparent advantages. Since it
never leaves the ground, it is totally recoverable and
reusable. Also it can be made as large as needed.
However, it does have drawbacks. By necessity, it must
be miles long. In addition, it is horizontal, although
an inclined track is an attractive possibility,
especially in the early science fiction movie When
This concept, although visually
attractive, does have its problems. The movie concept
has the spaceship initially blasting down before
abruptly changing direction and heading up the side of a
mountain and leaping into space.
The physical reality is that
all the kinetic energy initially built up going down is
lost when the spaceship reaches the bottom and starts to
Not so apparent are the lateral
stresses placed on the spaceship by radically changing
direction, increasing the weight of the airframe. It
does have the advantage of an upward trajectory,
although still requiring some sort of aerodynamic
lifting capacity, again increasing spacecraft weight,
because the rockets aren't firing vertically. The best
application of this idea is a ramp inclined at a
constant angle. Again, the spaceship has to have
aerodynamic lift until it attains sufficient velocity.
Another concept very popular during
the 1950's was launching the vehicle in sections and
assembling it in orbit. A variation on this idea was to
launch the spaceship empty and fuel it in space.
Although this idea would seem to solve many problems
associated with going to the Moon, I suspect it was
considered too complicated and risky to be seriously
considered in the 1960ís, where beating the Russians to
the Moon was a prime consideration.
Another concept of the 1950ís was
to carry a rocket to an extreme altitude using a giant
balloon, and launch the rocket at altitude, bypassing
most of the atmosphere. That was actually done with
research rockets to increase their maximum altitude. The
main drawback to this idea was that the maximum weight
of the rocket was limited by the load-carrying capacity
of the balloon.
Last but not least is a variation
of the nuclear pulse rocket idea. In this case a nuclear
device is used to launch a spaceship. Basically, the
device is buried underground in an extinct volcano and
the spaceship is set on top of it. When the nuclear
device is detonated, most of the force is directed
upward, launching the spacecraft. Among the problems
with this method are that a heavy and elaborate system
of push plate and shock absorbers is required to make it
work, and the launch site is unusable afterward.