Microlaunchers Synopsis

CREATING A PATHWAY TO SPACE

Charles K Pooley [email protected]

[email protected]

(702)438-5487

Blair J Gordon [email protected]

[email protected]

(614)434-6027

MICROLAUNCHERS

THE PREMISE

In view of recent events, it appears that entrepreneurial space is taking two main forms: suborbital

passenger service and low orbit satellites.

An example of the first is Scaled Composites and the newly formed Virgin Galactic. An example of the

second is SpaceX.

Both have in common a plan to make a profit in an expensive and uncertain environment. Much of the

stress and efforts of this type of venture will be centered around the investment/profit issues, with less

emphasis on the technology development, at the very time technology development is needed.

The Wright Brothers were not at first trying to set up a business. They were trying to build an airplane.

Microlaunchers is an attempt at a third approach to developing space access: to, with miniature size

and budget, develop a vertically integrated spacecraft launch/deployment system.

The system or portions of it then can be expanded with confidence after the initial system has proved

itself.

MICROLAUNCHERS

CURRENT DIRECTION

Space tourism is getting the most press because of the

recent X-Prize and plans to build a huge new industry.

It's not going to be that simple. If any of these do

actually start flying paying passengers, the business

and financial risks are so great that the effort will be

focused on making it succeed and not developing

access to space--to at least delivering people to a LEO

satellite.

"Tabletop spacecraft" refers to efforts to develop some

device, satellite, or even space a station module without

first developing the launch means. At the start of the

non-NASA space age, means to get there must come

first. An air show cannot precede the airplane.

The satellite launch service to deliver the current types

of satellites weighing hundreds to a few thousand

pounds will confront a problem: Those with such

satellites tend to have in their long involved construction

process the choice of available launcher already

factored in, together with the attendant costs.

Also, there are just too few of these to support a new

business centered around a new launcher. A good

example is the Orbital Sciences Pegasus air launched

system. In 15 years there have been a total of only 36.

Too few and infrequent to allow a launch cost

breakthrough.

MICROLAUNCHERS

SMALL & INEXPENSIVE

To develop a low cost basis from which an industry can evolve, a launch system must fly very

frequently and be very small.

I mean small: The Wright Brothers did not build a DC-3. They built something that barely carried two.

The launch system must be so simple to operate that some launchers might be kept on standby for

launch at a Near Earth Object--very small asteroids which pass by daily, some of which being

reachable for photo flyby. With a small in-house organization (Wright Brothers

being a good example) the components of the system

should be developed incrementally.

The testing and licensing of the stages should be done

incrementally, so each stage supports testing of the

next.

MICROLAUNCHERS

THE SYSTEM

The system needs to be complete, from launch to tracking and controlling the ascent, with initiating abort if

needed, to release of a detachable payload.

By perfecting a first generation of very small launcher/spacecraft combination, and using a high launch

rate the cost basis for all scaled up versions to follow would be minimized. Also, the skills to launch and

manage spacecraft would develop.

Later, with subsequent funding, a ten times increase of mass can enable a considerable increase in

payload mass. A second generation launcher with a gross liftoff mass ten times greater could allow a mass

of 50 pounds to escape velocity, allowing about 20 pounds to be soft landed on the moon or a Near Earth

Object.

MICROLAUNCHERS

LEO OR ESCAPE?

The Microlauncher system would not even get involved with Low Earth Orbit.

MICROLAUNCHERS

LAUNCH VEHICLE

The major component of the system is the launch vehicle. This is to use 3 stages, each using a type of

staged combustion engine derived from a single "prototype engine". The right funding might support

development of a staged combustion turbo pump engine, to be used for the first stage.

MICROLAUNCHERS

LAUNCH VEHICLE

The first stage is to deliver the upper two to an altitude having near vacuum conditions--about 60 to 70 Km

(200,000 to 233,000 feet), while having the vertical momentum to continue to about 100 Km. This "lofted"

trajectory permits a more horizontal attitude for the second stage, in a way similar to Shuttle launches. The

initially planned horizontal component is to be low for easy recovery and because the first stage, having

greater mass and lower specific impulse, will leave the task of accelerating to the upper stages. Here, 600

m/sec at 30 deg. latitude gives a possible eastward velocity of 1 Km/sec.

The second stage will operate in a vacuum, and have a higher specific impulse and lower empty mass

because the operating pressure can be lower and no aerodynamic provisions are needed. Carrying the third

stage, it is to increase the horizontal velocity by about 4 Km/sec. The structure will be mainly thin wall

aluminum tubing tanks and a low pressure engine. The tank pressure is to be about 10 atmospheres and the

engine pressure 5 atmospheres.

The third stage is to make use of very thin electroformed nickel structure and use a low tank and engine

pressure to allow a very low empty weight. The tank pressure is to be about 0.38 MPa (57 psia), the vapor

pressure of liquid oxygen at 105 deg K; and an engine pressure of about 0.15 MPa (1.5 atm). The low

pressures are to allow low mass and radiation cooling of part of the engine.

It is to accelerate and increase the horizontal velocity by about 6 Km/sec, so that the horizontal velocity will

exceed 11 Km/sec, the escape velocity from the altitude at which the third stage is out of propellants.

An optical guidance based on a camera looking at the sun and the earth horizon is to be carried on the

stage, and is to guide the second and third stages. Optical tracking from the launch site will enable

adjustment or termination of the flight.

MICROLAUNCHERS

LAUNCH VEHICLE

Recoverable First Stage

Shown here is the turbo pump engine version.

The structural layout of the pressurized

propellant version is more complicated because

it requires a larger number of smaller diameter

tank tubes.

In either case, there is to be two engines--one,

the "sustainer" of about 1000 pound thrust, and

the "booster of over 2000 pounds thrust. Both

operating together are to accelerate the

launcher to a high subsonic velocity, say, 250

m/sec, at which time the booster engine shuts

off and the sustainer continues. This is to allow

the small launcher to climb through the denser

part of the atmosphere quickly but without

aerodynamic loads becoming too high. This type

of ascent is more optimum for small vehicles

more subject to aerodynamic drag than the

usual larger launchers. It is not to reach

supersonic speeds until the altitude is over 5 to

10 Km.

The propellant tanks are the main structure, with

the engines and fins at the lower end, a "wing

box" at an adjustable point near the center of

gravity, and the upper stages within an

enclosure at the upper end. The wings are to

extend in a manner similar to those of a cruise

missile, after the stage has decelerated to a low

subsonic velocity.

MICROLAUNCHERS

LAUNCH VEHICLE

The Launch Trajectory

At launch there is a short high

acceleration period in which the velocity

reaches 250 m/sec in about 8 to 12

seconds at an altitude of about 2 Km

(6000 ft). The sustainer continues the

acceleration to the velocity of about

1200 m/sec (Mach 4), at which time the

engine is to throttle down to a low thrust

to maintain enough acceleration to keep

the propellants settled at the bottom of

each tank.

The stage is to orient itself to the pitch

for launch of the second stage at an

altitude of about 60 Km, while the

vertical velocity is still about 900 m/sec.

The second stage is to accelerate

nearly horizontally toward the east to

take advantage of the earth rotation of

about 400 m/sec if the latitude is 30

degrees.

MICROLAUNCHERS

LAUNCH VEHICLE

The Deceleration and Recovery

For recovery, airbrake panels are extended

and locked open at high altitude, and these

panels help the final velocity after reentering

denser air to become low enough for the

extension of wings to be done without too

much power required. The velocity might be

100 m/sec indicated speed (equivalent

speed at sea-level).

The wings are to extend and the brake

panels retract while the stage is still

descending vertically so there is no lift to

make the extension difficult. An on-board

accelerometer and gyroscope is then to

control a pullout maneuver at, say 3 G's, and

to finish the pullout with the stage gliding

horizontally.

A pitot tube on the nose is to then maintain a

steady glide speed of, say 40 m/sec (78

knots) by controlling the pitch. The stage is

then to glide in this way until it is picked up

and taken in tow by a small aircraft. The

towing force will be less than 50 pounds.

MICROLAUNCHERS

LAUNCH VEHICLE

The Propellant Management System Each propellant tank is to be a self

contained unit with a capacitive depth

sensor, shutoff valve and a motor driven

variable partially restricting valve.

A comparator circuit is to measure the

contents of each tank in turn at, say one

complete cycle each second, and cause an

incremental increase in opening of the

valve of the tank least depleted. In each

cycle the tank most depleted will have its

valve closed by a small increment. This is

to cause all the tanks to drain together,

with little or no residual of contents. This

will work with any number of tanks and any

number of propellants (a first stage version

might use water as coolant).

MICROLAUNCHERS

LAUNCH VEHICLE

Staged combustion engines

The engines are to use a 'pre-burner' to

change the LOX to a high pressure gas which

is to enter the engine at perhaps 100 m/sec.

This will facilitate the atomization of the fuel

and permit a wide range of throttling, because,

in lowering the thrust only the oxygen gas

pressure changes, not its volume. The range of

thrust may be more than ten to one.

The preburner is to be able to operate by itself,

using servos to control the temperature and

pressure of the oxygen. The oxygen is to pass

through a nozzle in order to isolate the

preburner from the combustion chamber

downstream. An oxygen to fuel ratio of 100 to

1 will produce a gas temperature of about 60C.

MICROLAUNCHERS

LAUNCH VEHICLE

Staged combustion engines (cont.)

The preburner will then be coupled to the remainder of a test engine in order to test the fuel atomization and

a property called characteristic velocity--an indicator of the engine performance.

The test engine will be water cooled with measurement of the heat conducted from the chamber being

measured. This is to confirm the choice of regenerative cooling method.

The numbers given here are preliminary

estimates that the prototype engine is to

confirm. The engines for all three stages are

to then be designed as a scaling up or down

of size and pressure. If funds are found to first

develop a turbo pumped engine, that will be

used for the first stage.

MICROLAUNCHERS

LAUNCH VEHICLE

Staged combustion engines (cont.)

The third stage is to be constructed almost entirely of electroformed nickel. With this method there is no

"minimum gauge problem"--the problem of finding materials that are thin enough for small low pressure

tanks.

The LOX and propane fuel tanks are to use three identical nearly spherical shells coupled in a way to be

published later.

The propellants and a small capsule of liquid

nitrogen will be kept at 105 degrees K, at which

the pressures of the three liquids will determine

the feed rate and engine pressure.

The engine is to operate with a low chamber

pressure--perhaps slightly higher than one

atmosphere, so that the lower heat flux will allow

major parts of it to be radiation cooled at a

reasonable temperature.

This low chamber pressure will also allow more

extensive testing, designing of the injector and

combustion chamber in a testing environment that

is simpler than the usual test stand.

MICROLAUNCHERS

AFTERNOON LAUNCH

The path likely for a successful launch slightly over the escape velocity and using an eastward launch in the

late afternoon will become a slightly elliptical solar orbit, with most of it being beyond Earth's orbit. This way,

it will tend to be in line-of-sight at night for the first 6 months or so.

After confirming a velocity in excess of

escape minutes to an hour or so after

launch, the main next stage in developing

the Microlauncher system will be the means

to keep a detached payload oriented and in

communication with a place on Earth. The

plans for developing this will be published

later.

MICROLAUNCHERS

FLIGHTS / MISSIONS

At first, the launches will be centered around the launcher performance, and there would not be a

detachable payload. The launchers will support spacecraft development, diode laser link tests, and perhaps

to pursue some revenue possibilities such as sending to solar orbit samples of cremated remains. With an

in-house launcher, this becomes a possibility.

MICROLAUNCHERS

FLIGHTS / MISSIONS

Later, there would be tests of a spacecraft structure which can maintain 3 axis orientation with

solar radiation pressure and no use of consumables, and a point able laser diode data link. The

data link design details will be published later.

Then, a small cold gas thruster system using room temperature ammonia will be designed to

give a velocity deviation capability of 100 m/sec.

A complete spacecraft might have built in the electronics of an off-the-shelf digital camera.

Stripped of the packaging, these weigh very little and can offer megapixel quality images rivaling

those from NASA not many years ago.

The issue of radiation hardening can be explored by observing the condition of the electronics

over months. Many NEO's can be reached in a relatively short time, so commercially available

electronics may last long enough to be useful.

Another important product of many cheap launches will be the development by a substantial

number of people the navigational skills which are vital to opening access to the solar system.

This is what happened with computers. Millions have them and have developed the skills to use

them. A social revolution.

MICROLAUNCHERS

FLIGHTS / MISSIONS

Some NEO's (which could someday be called Microlauncher targets) pass Earth at a velocity low enough so

that rendezvous and controlled landing may be possible. The guidance for such a lander can make use of

the chips used in an optical mouse. Because of the way they operate, the guidance will tend to allow the

approach velocity, deceleration and distance to converge on zero together so the craft would not bounce off.

The escape velocity of many of NEO's is less than 1 foot/sec.

The guidance might use a small diode laser as

a LIDAR, and one mouse chip to control the

transverse movement while the LIDAR controls

the descent. Or it could be wholly passive,

using 3 or 4 mouse chips which together

measure the movement in 3 axes.

MICROLAUNCHERS

DEVELOPMENT The project and funding of it will be done

in a piecemeal fasion, possibly combining

with partners interested in a development

of one or more of these subsystems.

SBIR or DARPA funding might likewise be

sought for a subsystem as a separate

project. In time, it is hoped that this will

eventually add up to the Microlauncher

System.

MICROLAUNCHERS

ENGINE

The first stage of the small Microlauncher will probably use a pressurized propellant system, but for a scaled

up launcher, a turbo pump type engine would avoid the need of large high pressure tanks and to take

advantage of the higher performance and lighter structural weight possible.

If a partner were to be found who was interested, this engine type might be developed earlier and used in

the small Microlauncher.

MICROLAUNCHERS

ENGINE

The preburner developed for the upper stage engines would be scaled up in size and pressure to drive a

turbine with oxygen gas at a moderate temperature, say, 500 to 600 K (230 to 330 C) so the materials for

the turbine and associated parts can be of copper, bronze, or monel. The Russian RD-170 uses an oxygen

temperature of 772 K in order to get the power to support a very high chamber pressure. For a lower

pressure of, say, 3.3 MPa (500 psi), calculations show that the lower temperature is sufficient.

As with the non-turbopump type, the high velocity oxygen will allow effective atomization of the fuel, or

possibly there might be a fuel preburner which uses some of the LOX from the pump to heat the fuel enough

so it enters as a gas or supercritical fluid. Having no surface tension the fuel will not form drops and no

atomization will be required.

The design process is still underway, but it appears that this engine type can be throttle able over a wide

range and be lighter and more efficient than the pressurized type.

Incidentally, I am using SI measurements for the actual design calculations because pounds, slugs, pound,

square feet etc is just too confusing. Also, English units caused loss of a Mars orbiter once.

MICROLAUNCHERS

ENGINE

The preburner developed for the upper stage engines would be scaled up in size and pressure to drive a

turbine with oxygen gas at a moderate temperature, say, 500 to 600 K (230 to 330 C) so the materials for

the turbine and associated parts can be of copper, bronze, or monel. The Russian RD-170 uses an oxygen

temperature of 772 K in order to get the power to support a very high chamber pressure. For a lower

pressure of, say, 3.3 MPa (500 psi), calculations show that the lower temperature is sufficient.

As with the non-turbopump type, the high velocity oxygen will allow effective atomization of the fuel, or

possibly there might be a fuel preburner which uses some of the LOX from the pump to heat the fuel enough

so it enters as a gas or supercritical fluid. Having no surface tension the fuel will not form drops and no

atomization will be required.

The design process is still underway, but it appears that this engine type can be throttle able over a wide

range and be lighter and more efficient than the pressurized type.

Incidentally, I am using SI measurements for the actual design calculations because pounds, slugs, pound,

square feet etc is just too confusing. Also, English units caused loss of a Mars orbiter once.