The hulls of the landing craft were arranged with the pilot's compartment far forward, with seats for pilot, copilot, flight engineer and radioman. It had wheel controls and a mighty instrument panel. Hidden by the latter and jammed forward into the nose section were various electrical devices and the automatic course-keeping equipment, which would come into play when the wingless hull took off rocket-fashion to return to a satellite orbit.
Abaft of a small radio bay was a large cabin for the personnel and equipment of the landing party. It was about four meters long and filled the whole cross-section of the hull, thus exhibiting no marked distinctions from the cargo space of a medium-sized transport.
In its center, just atop a hermetic loading hatch, was the location for a special caterpillar for Mars. This could be passed through the hatch after landing by means of lowering tackle attached to the ceiling. Surrounding the vehicle there was ample room for food and other supplies. Flat couches for some 18 persons lined the walls, which had two rows of port holes for exterior vision of the occupants of the couches.
Still further aft were two large propellant tanks, most of whose contents would be required for the rocket takeoff from Mars. The tankage bay was some 7.5 meters long.
In the afterbody were located the turbopump, the gas generator, and the valves and tubing of the rocket propulsion unit, with the motor proper at the extreme tip. Despite this motor's ability to develop the same 200 ton thrust as the top stage of a Sirius ship, the diameter of its discharge nozzle was but half the latter's. This smaller diameter pointed to the contemplated use of the motor in the Martian atmosphere.
There had been an early decision to fly the landing craft into the terrestrial satellite orbit without disassembling, unlike the space vessels proper. This could be done by putting them in the place of the top stage of a Sirius vessel, and permitting the two Sirius boosters to lift them to a point where their own rocket plants could take over and provide the final velocity increment for attainment of the orbit. Their enormous wings, of course, would be dismounted, being freighted up in sections in the course of the regular supply operations. Then they would be reassembled in space and mounted on the hulls prior to the final departure.
The master plan called for a special expedient applying to the ski-equipped landing craft only. This craft would, of course, need the same propellant capacity as the others in order to reach the orbit of departure. But since it was to be abandoned after landing near the Martian South Pole, it would need no propellants for the return. It had been computed that each landing craft would expend but 15 tons of its total propellant tankage of 128 tons to depart from the satellite orbit around Mars and to land on his surface, the remainder being needed for return to the orbit. The 113 tons in the ski-equipped craft would thus be available for other purposes. Holt suggested that considerable supplementary equipment to ease the exceptionally difficult problems of the first landing party be made available to them in the extra load thus disposable.
It was decided to remove the large plastic tanks of the ski-equipped craft in the terrestrial orbit and to replace them with smaller ones which would suffice for the landing maneuver on Mars. That made available a volumetic capacity of some 12 meters by 4.5 meters in diameter which could carry a weight of not less than 125 tons of pay load, where the other landing craft had but 12. Three big caterpillars would be the key equipment of this cargo, and with them the landing party would find itself with adequate transportation for the long trip towards the Martian equator.
The Mars vessels themselves were under construction in one of the other buildings, but the onlooker could as yet discern but little of the clumsy outlines of these, the backbones of the expedition. Here and there isolated groups were being check-assembled and then taken apart again for shipment into the orbit of departure.
A casual glance into the great building conveyed the impression that one of the old harbingers of the air age was being resurrected, to wit, a rigid dirigible like those which successfully attacked the Kingdom of the Air some eighty-odd years before. The enormous propellant tanks of plastic fabric, thin, folded and empty, lay in stacks one upon the other and were reminiscent of hydrogen or helium ballonets from the tanks of the long departed Zeppelins. Not far distant, the noise of riveting hammers echoed through the filigree tracery of tubular trusses like those of some arched bridge. Eventually the tanks would be suspended in these structures. All long frames were sectional, connected by screw joints at certain intervals, for easy stowage in the holds of Sirius vessels.
One of the spherical personnel nacelles for a passenger vessel was inflated in one corner of the great assembly hall. It was blocked up on a flat, wooden stand, appearing for all the world like a glistening, silver balloon some ten meters in diameter. Within it, a crew of men were working on the interior fittings, having entered by the already completed entrance airlock by which the moderate internal pressure was prevented from escaping. The job in hand was to adapt and fit the electrical wiring and the rubber tubes for the air circulation system. When completed, these, like all the other fittings, would again be removed so that the nacelles might be freighted up to the departure orbit collapsed, like the propellant tanks. There it was that the final assembly was to take place.
In the upper part of the nacelle was the control room. This would be the foremost element of a Mars ship after final assembly and would contain a bewildering assortment of gauges, gyro gear, radio equipment and operating panels. The uppermost segment, which would form the extreme nose of the space vessel, was the forward astrodome.
Through it or through one of the seven others strategically arranged around the sphere, all angles could be visually covered. Each astrodome was a hemispherical glass bowl about one meter in diameter, through which the navigators might take the stadimetric angles of heavenly bodies required for running fixes. Light could enter the nacelle through a large number of smaller portholes liberally interspersed between the astrodomes.
The deck below the control room in the spherical nacelle contained four sleeping compartments segmentally arranged around its periphery, as was the Captain's cubicle.
The next lower deck was composed of two large living compartments, a radio office and a small library which might also be used as a chartroom. On this same deck, air and water regeneration equipment was located, and space was left for a sick bay, a toilet and Peyton's famous garbage gun. The part of the great sphere that would be closest to the propellant tanks after final assembly contained the galley, the food storage and a water tank. The entrance airlock was at the very bottom. Communication between the various decks was through central and concentric openings through which ran a fireman's pole, for the weightless condition which would obtain throughout the voyage rendered any sort of ladder or stairs superfluous.