[FPSPACE] NASA To Build ISS Propulsion Module Around Node Test Article

JamesOberg@aol.com JamesOberg@aol.com
Fri, 22 Sep 2000 08:57:40 EDT

NASA To Build ISS Propulsion Module Around Node Test Article 
by Frank Morring Jr  // Aerospace Daily  //  09/21/00 7:08:47 PM U.S. EDT 
    NASA's Internationl Space Station program has decided to recycle the 
structural test article for the Unity Node as the U.S. Propulsion Module, 
which will backstop Russian hardware to raise the Station's orbit and 
maneuver it out of the way of orbital debris. 
     Boeing will build the new module, working under a planned change order 
to its prime Station contract with NASA, according to the top Station 
official at agency headquarters. The space agency halted work at Boeing on an 
earlier version of the module when costs crept more than $200 million above 
the $540 million budget. 
     Now that the Station (shown in NASA photo after STS-106 mission work) 
includes Russia's long-delayed Zvezda Service Module, the primary source of 
reboost and maneuvering propulsion on the orbiting facility, NASA has also 
decided to keep its Interim Control Module (ICM) on the ground, according to 
Mike Hawes, deputy associate administrator, space flight development. Instead 
of launching the ICM to Station, where it cannot be refueled, the modified 
Shuttle-compatible upper stage will be maintained for callup to meet a 
variety of contingencies that might arise, he said. 
     Hawes told reporters Thursday afternoon the Station program selected the 
"Node X" option over a concept that would have attached engines, fuel tanks 
and other propulsion elements atop the Z-1 truss that is to be launched 
aboard the Space Shuttle Discovery Oct. 5. 
     The module, tentatively scheduled to be launched to the Station in mid- 
to late-2004, will consist of the Boeing-built node and at least one 
replaceable propulsion element attached to its starboard berthing port. The 
propulsion element will contain engines and tanks to hold the hydrazine 
monopropellant fuel, while propulsion avionics will be housed in the 
pressurized node. 
     Although NASA decided to give the work to Boeing because it built the 
structural test article that will be the module's foundation, Hawes said the 
change order will include "make or buy" provisions designed to hold open the 
opportunity for competition at the component level. Some of the hardware, 
chiefly mutliplexer-demultiplexers, has been bought as long-lead items for 
the original Boeing concept, and the test article itself has already been 
modified to meet pressure-test requirements it failed originally. 
     "We are just initiating the detailed discussions with Boeing to start 
this work off, so we don't have any real firm schedule milestones as yet," 
Hawes said. "Our internal estimates are that we will probably b y next March 
or so have an integrated plan with Boeing that will have a better view of 
cost and schedule for this option." 
     The module will be mounted in front of the planned Node 2, now under 
construction at Italy's Alenia, with the single propulsion element riding in 
front of the European Space Agency's planned Columbus module. Hawes said the 
single element could handle 50% of the Station's expected propulsion 
requirement, and a second element could be attached to the node if more 
capability is needed. 
     When the module is needed for Station reboost, the entire orbiting 
facility will be rotated through a 180-degree yaw maneuver to put its engines 
in position to raise the orbit, Hawes said. A pressurized mating adapter at 
the front of the propulsion node will give Shuttle crews access to the 
Station, and some of its interior volume will be available for storage, he 
     NASA decided last summer not to make the modifications necessary for the 
Shuttle fleet to be able to refuel the Propulsion Module in orbit, opting 
instead for a concept that would have the module broug ht back to Earth for 
refueling . Hawes said the issue of how many propulsion elements to build is 
still under study, as is the exact size of the element. With the Station 
requiring an average of 7,000 kilograms of propellant a year, the propulsion 
element will weigh on the order of 25,000 to 30,000 pounds, he said. 
     "I personally would like to see us go through the sizing to make su re 
it is an item that we can co manifest with other Space Station resupply 
items, and that's the goal that we have in going through this," Hawes said. 
     Although it was originally planned when it wasn't clear the Russians 
would be able to deliver the Zvezda Service Module, Hawes said the Propulsion 
Module is now intended as one among many sources of propulsion that will be 
available to Station operators. In addition to propulsion supplied by Zvezda 
and Russia's Progress resupply capsules, Hawes said, Station reboost also 
will be provided by visiting Space Shuttles and the planned European and 
Japanese orbital transfer vehicles. 
     "We believe that the Prop Module enhances the overall robustness of the 
Space Station," he said.