Tag Archives: spaceflight

Satellite tracking

A Cygnus cargo spacecraft was launched to the International Space Station (ISS) on May 21, 2018. Among the supplies that it carried were nine small educational and commercial satellites know as CubeSats. One of the satellites is named EQUiSat. It was designed and built by Brown Space Engineering (BSE) undergraduate students.

Four of these satellites were released on July 13, 2018 from the ISS by astronauts using a device called the NanoRacks CubeSat Deployer. They were ejected at about 1.5 m/.s (3 mph.) Initially they were spaced about 10 to 50 cm (4 to 20 inches) apart. They quickly moved ahead of the ISS together in a cluster as the distance between them more gradually increased over time. EQUiSat is the second cube from the right.

Deployment of a CubeSat flock
Deployment of a “flock” of four CubeSats from the ISS on July 13, 2018. Credit: NASA

Below are maps showing the ground track of the small satellites as they orbit 400 km (250 miles) above the Earth. Also shown are the paths they take across the sky as they pass above the radio ground station at Ladd Observatory. Traveling at a speed of 27,600 km/h (17,100 mph) it takes only 92 minutes to orbit the Earth.

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EQUiSat 1.0 (and future revisions)

Idea for EQUiSat 2.0: “Hall thruster powered by LiFePO4s – to go to the moon”

―Mckenna Cisler ’20, Brown Space Engineering

It began as a thought experiment for a class in 2011: “Developing a mission plan for a space related project.” On July 13, 2018 that plan became a reality when astronauts aboard the International Space Station (ISS) deployed EQUiSat. Undergraduate students from the Brown Space Engineering (BSE) team had designed and built a “cubesat” which NASA then launched on a cargo supply mission to the ISS in May of 2018. After deployment it started transmitting data from low-earth orbit to an antenna on the roof of Ladd Observatory and another ground station at Sapienza in Rome, Italy. In the words of former team member and class of ’14 astrophysicist Emily Gilbert: “***IT’S ALIVE! IT’S ALIVEEEEE!!!!***

Constructing EQUiSat
Hunter Ray working on EQUiSat in the Brown Space Engineering lab on Dec.10, 2017.

The idea for their mission was to test a new battery technology called lithium iron phosphate (LiFePO4) which had never flown in space.  While all space missions are risky using untested components for an important scientific mission or in an expensive commercial satellite is an unacceptably high risk. The students set out to build an inexpensive testbed to prove this technology. The satellite cost $3,776.61 to build. That price tag doesn’t include the countless hours spent by more than 200 students to design and fabricate the parts of the satellite. NASA agreed to launch the satellite for free. If the results look promising it could lower the cost of future space missions and enable new capabilities.

But the technical requirements of the mission are merely a backdrop for a broader vision. The real goal and larger dream of BSE mechanical engineer Hunter Ray ’18 is “For space to become more affordable and accessible to a community other than astronauts and rocket scientists and to be able to look up at the Moon and see the lights of the first permanent extraplanetary settlement.

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Fellow Travelers

“The radio signals of the satellite [Sputnik II] were followed and recorded on tape frequently by Mr. C. Newton Kraus, an outstanding radio amateur of Touisset Point, R.I. He had followed Sputnik I signals for the three weeks that the transmitters continued to function.”

―Charles H. Smiley, The First Artificial Earth Satellites, August 1958.

On October 4, 1957 the Soviet Union launched the first artificial Earth satellite which was called Sputnik I. The word Sputnik simply means “satellite” or, more generally, “fellow traveler.” The quotes from Prof. Charles Smiley, director of Ladd Observatory, are from a report published in The Hinterlands, the Bulletin of the Western Rhode Island Civic Historical Society. He describes how Sputnik I could be seen from all parts of the Earth and reports on the local observations of it: “In Rhode Island, between October 12 and November 27, it was observed at Ladd Observatory of Brown University on 13 different passages for a total of 33.2 minutes.” The observed positions and motion were plotted on a star map.

Observations of Sputnik I
Observations of the Sputnik I rocket body from southeastern New England. October 12-17, 1957.

The satellite itself was only 22 inches in diameter and would have been difficult to see from the ground. Instead, they were observing the rocket that launched the satellite which also entered orbit. The second stage of the rocket was 92 feet long and 9.7 feet in diameter. Sunlight reflecting off the rocket body was much easier to see. Notice that observers in Providence RI, Nantucket MA, and Mansfield CT saw the rocket in a slightly different position against the background stars due to parallax.

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Flight-critical calculator

“In addition to helping the crew organize its time, the second HP-41 computer was kept ready for flight-critical, deorbit-burn calculations. Once during each orbit around the Earth, the shuttle has an opportunity to land at one of six contingency locations. During a routine flight, Mission Control supplies the shuttle crew with deorbit-burn information. Should the shuttle encounter an emergency, however, the astronauts would rely on the HP-41 for these calculations.”

―”HP-41’s Again Aboard Columbia.” HP Key Notes, March-May 1982.

HP-41 advertisement
Hewlett Packard advertisement, 1982.

To prepare an orbiting Space Shuttle for re-entry through the Earth’s atmosphere it is critical that the spacecraft be “balanced” by taking into account the mass of the fuel left in the tanks at the end of a mission. An astronaut would use a handheld computer or programmable calculator to determine how many minutes and seconds of fuel to burn to get the center of gravity correct for a smooth descent and landing. The “personal computing system” used for this was made by Hewlett Packard in the 1980s. NASA donated one of these, a model HP-41CV, to Ladd Observatory after the retirement of the Shuttle program.

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