March 1982:the Percheron rocket

Non-government sponsored space programmes have been few and far between. Efforts such as that by the California rocket pioneer Robert Truax have yet to bear fruit but have stimulated the interest of others into trying to construct rocket carriers capable of reaching suborbital and orbital heights.

Space Services, Incorporated (SSI) of Houston is one organisation of entrepreneurs which plans to compete with the major commercial payload carriers, (the American Space Shuttle and Delta, and the European Ariane). Its vehicle programme centres about a rocket module similar in size to the Redstone that would be mass produced using low cost, high technology techniques, with only modular variations being required to produce different orbital configurations.

The Vehicle

The SSI vehicle is known as Percheron (after the French for workhorse). It is 1.2 m in diameter and almost 14 m tail; the addition of a nose cone and engine brings the final length to over 17 m. The pressure-fed engine has a potential thrust of 34,000 kgf, although the first prototype reached only 27,000, and uses a coaxial pintle system like that on expandable launch vehicles and in the Apollo lunar module descent engine system. This particular engine burns JP-4 kerosene as fuel with liquid oxygen as an oxidizer.

A gas pressurisation system is mounted on the nose to maintain tank feed pressure at 350 psi for both the kerosene and the oxidizer. A common bulkhead separates, fuel and oxidizer; it was the bulkhead which separated during the August 1981 catastrophe when the first rocket was destroyed during a static test.

A 4 m long payload section in the shapre of a truncated cone and capable of surviving reentry is carried. A number of expandable vanes lie at the rear to help to orient the capsule at the proper entry angle, thus controlling the rate of descent and downtrack/crosstrack imbalance. Parachutes, the reaction control subsystem for on-orbit adjustment and an avionics bay make up the remainder of the segment.

Other versions could be created by adding to this basic production model: a production model plus upper stage, and a production model/upper stage with strapon boosters. The upper stage could be either liquid or solid fuelled. Parallel staging (as in the Space Shuttle) occurs in the third version when two or more strapons plus the main engine fire simultaneously to increase the overall boost altitude prior to upper stage burn towards geosynchronous orbit. For a heavy payload, a cluster of seven modules is linked together; the outer six fire until four are depleted. These four are jettisoned and the remaining three fire together.

For the past 25 years the major space countries have used a wide range of rockets to boost payloads into space. Each of these countries’ programmes is weighed down with the encumbrances of government bureaucracies. SSI’s development efforts have concentrated on using rented launch sites, (eventual) rented tracking stations, minimal.support facilities, in-house consulting and the construction of partially reusable rocket components in order to minimise lengthy qualification and test cycles.

Percheron’s body is formed of a glass filament-wound fibre mainly because of the optimal weight and cost advantage. Use of aluminium and stainless steel is provided for in the various equipment support structures. Purchase of filament winding equipment is expected to comprise a principal expenditure for SSI’s production facility.

The SSI programme plans to run at a per flight cost of one-third that charged by NASA for a user contracted to fly on the Space Shuttle. In order to achieve this, the following techniques are employed:

1. Use of identical production engine modules

2. Cluster small systems rather than building large heavy lift single engines

3. Use of pressure-fed instead of pump-fed fuel systems

4. Use of low cost and easily obtainable fuel

5. Use of lightweight structural material

6. Use of recoverable payload sections

7. Use of "off the shelf" technology rather than existing military-grade equipment

8. Minimise programme management and personnel costs

9. Contracting with existing ground stations for data link rental

Space Services’ budget does not permit massive expenditures on launch sites, so for its first test a 3000 acre area was leased on Matagorda Island located off the southern Texas coast at latitude 27.9° North and longitude 97° West. Ironically, the island is in the same locale that NASA was considering 20 years ago as its prime candidate for a southern launch site. Cape Canaveral was later selected.

Following the August 1981 setback, Space Services planned to rebuild in California, estimating only six months completion time for the second model. Qualifying the propulsion system seems to be the major problem; its schedule showed about 200 test firings.

An orbital test launch was planned for early 1983 and preliminary talks have already taken place with the US Air Force with the intention of using Vandenberg Air Force Base in California for possible polar low Earth orbit missions, with future thoughts of lifting up to 2300 kg payloads.