NanoRacks Identifies Root Cause of ISS Cubesat Deployment Failures

by

TORONTO — Two August failures of the NanoRacks satellite dispenser operated from the international space station — one a nondeployment of small satellites and the other an unplanned release of spacecraft — were both caused by overly tightened dispenser screws, Houston-based NanoRacks has concluded.

NanoRacks LLC Managing Director Jeffrey Manber said the company has repeated the failure at a ground test facility in front of NASA. Sometimes there is no deployment, and sometimes deployment occurs without being commanded.

Manber said NASA, as space station general contractor, and the Japan Aerospace Exploration Agency — from whose station module the NanoRacks’ dispensers are deployed — have approved the company’s decision to deliver a fresh batch of dispensers to the station. But the two agencies are still assessing possible additional safety measures, such as mandating that a latch be put on the dispensers’ covers to prevent unplanned deployments.

As an added precaution, Manber said, NanoRacks has hired the Aerospace Corp. of Los Angeles, a U.S. federally funded research and development center, to oversee the company’s review of what happened.

In an interview here at the 65th International Astronautical Congress, Manber stressed — and NASA in its summary of the event agreed — that the unscheduled release of the two satellites at no time posed any threat to the station crew or the station’s infrastructure.

“This is a commercial project, and we have to accept the possibility of failures,” Manber said. “But we have to assure that any failure does not pose a threat, and this posed no threat. We are getting our space legs. If this had happened on an expendable launch vehicle, of course, the satellites would have been lost.”

The satellites owned by Planet Labs of San Francisco that were released in an uncontrolled fashion did not suffer from the experience. The satellites that were not released are similarly in good health.

Manber said two of the dispensers aboard the station — the ones whose satellites did not deploy on command — would be returned to NanoRacks for inspection. NanoRacks is now more closely calibrating the tightness of the screws before they are prepared for packing into the space station cargo freighters.

“This was a case of our not fully understanding how sensitive to screw tightness of the dispensers were,” Manber said.

The dispensers, rectangular cylinders with a door at the end, each house up to several cubesats — satellites measuring 10 centimeters on a side and typically weighing only a few kilograms.

The dispensers exit the station from JAXA’s Kibo habitable module. They are then seized by Japan’s robotic manipulator arm and placed into the correct release orientation.

NanoRacks’ business has become centered on cubesat deployments because the number of cubesats  built by commercial companies is skyrocketing. NanoRacks has placed more than 150 payloads on the space station and has more than 100 more awaiting delivery, NanoRacks Business Development Manager Richard Pournelle said here in a presentation of the company’s business.

Pournelle said NanoRacks has booked four orders from customers seeking to deploy satellites weighing up to 50 kilograms, and the company is aiming to accommodate 100-kilogram-class satellites.

The international space station operates at an altitude of between 390 and 410 kilometers, its orbit inclined 51.6 degrees relative to the equator. While not ideal as an Earth observation orbit for some missions because it does not cover the whole planet, the station’s orbit overflies 95 percent of Earth’s surface and is located under the radiation belts that can disturb satellite operations and cut their service lives.