spaceflight – Page 409 – Behind The Black

An contract extension from NASA for SpaceX and Sierra Nevada

June 27, 2014 3:18 pm Robert Zimmerman

NASA has given SpaceX and Sierra Nevada six additional months, until March 2015, to complete their last contractual milestones for building their manned spacecraft.

An amendment signed by William Gerstenmaier, NASA’s associate administrator for human exploration and operations, on May 16 gives SpaceX until March 31, 2015, to complete the 14th and final milestone under its $440 million CCiCap agreement — a pad abort test of its Dragon capsule. The test originally was planned for April 2014.

On May 19, Gerstenmaier signed a similar amendment to Sierra Nevada’s $212.5 million CCiCap award to extend work associated with flight tests of the company’s Dream Chaser engineering test article until March 31, 2015.

NASA’s third Commercial Crew partner, Boeing, is on track to complete all its milestones, worth a combined $460 million, by the end of August,

The significance of this extension is that it reveals something about the dates for both SpaceX and Sierra Nevada’s next flight tests. The previously date for the pad abort test for Dragon had most recently been set for this summer. They are obviously not meeting that schedule and need more time. Sierra Nevada meanwhile wants to fly its Dream Chaser test vehicle some more, but apparently needs time to get it flight ready after it sustained damage during landing on its one and only flight test.

In addition, this extension suggests something about NASA’s assessment of the efforts of all three companies. The agency is supposed to down select to two companies by the end of the summer. The extension suggests that they are hoping to keep all three companies funded so that they all build their spacecraft.

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Communications to be lost with the Stereo spacecraft

June 27, 2014 9:53 am Robert Zimmerman

Communications with the two solar-observing Stereo spacecraft will be cut off for more than a year, far longer than originally expected, as their orbits move them behind the Sun.

Unexpectedly high temperatures in the high gain antenna feed horns on both STEREO spacecraft will require corrective action in the coming months that will severely limit science operations. The high temperatures are being caused by the small angle between Earth and the Sun as seen from each spacecraft. In other words, pointing the antenna at Earth is putting too much solar heat on the antenna feed horn. To bring down the feed horn temperature, and preserve the spacecraft for years to come, the antennas will be pointed off at an angle from both Earth and the Sun, so that less heat will fall on the feed horns. Communication will still be possible using one of the antenna side lobes, but the telemetry rate will be extremely low. What instrument operations can be supported while the antennas are off-pointed is still being studied.

The spacecrafts’ orbit allows them to observe the back side of the Sun not visible from Earth. Though engineers had expected to lose communications for a period of time when the Sun moved between the spacecraft and the Earth, the blacked out time period has turned out to be much longer than planned. The shutdown will begin later this year with communications not resuming until January 2016.