Origin of CubeSat Bob Twiggs

The general idea for CubeSat was developed in 1997 while working the Stanford OPAL microsatellite, which as later used with The Aerospace Corporation to launch picosatellites (weighting less than 1 kg). The Space Systems Development Laboratory started on the OPAL satellite in 1995 after a special research class directed by Prof. Tom Kenny and Prof. Bob Twiggs to explore developing picosatellites and launching and launching them from a mother craft. The requirement by JPL for a picosatellite was to measure the earth’s magnetic field with a magnetometer in a spinning picosat like the one shown figure 1 below.

Figure 1. Early Picosatellite Developed by Mike Hicks at Stanford

The launcher, however, developed for this picosat would have made Rube Goldberg cry. It had several motors as shown in Figure 2 (not shown yet) and very seldom was successful in a practice launch of a picosat.

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Figure 2. Round Picosat Launcher for OPAL Ernie Robinson at The Aerospace Corporation was interested in launching picosatellites. At a conference at AFRL in Albuquerque in early 1998, a meeting between Al Pisano, Ernie Robinson and myself resulted in the DARPA funding the completion of OPAL and the development of picosats by The Aerospace Corporation. Al Pisano was director of the MEMS program for DARPA at that time. It was determined that a new launcher needed to be designed for OPAL. Ernie dropped the criteria for a round picosatellite that was spun up at launch. With this it was decided to make a flat picosatellite about 3 “ x 3” x 1”. After several designs for holding the picosatellite in the launcher, the launcher prototype shown in Figure 3 was built.

Figure 3. First Picosatellite Launcher made from Korian

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This launcher was made from Korian counter top material in the shop of Advanced Counter Top in Santa Clara, California. This shop belonged to my son Mark Twiggs, so I could work in it late at night. The Korian was an excellent material for making models of the type shown. This concept held the picosatellites on a chamfer on the corners to minimize the contact with the picosatellite surfaces. There was clearance for the picosatellites to exit the launcher. The final launcher is shown in Figure 4 along with the Korian prototype.

Figure 4. OPAL Picosatellite Launcher shown with the Prototype Korian Model The foot propelled by the spring ejected the picosatellite when the launcher door was opened. To keep the picosatellites from rattling in the launcher, a chamfer was made on the pusher foot and the door to push the picosatellites to the side of the launcher and lock them in when the door was closed. OPAL was launched by the USAF Minotaur expendable launch vehicle in January 2000. After some initial difficulty with the ground operations with OPAL, the picosatellites were released. There were two 4” x 3” x 1” picosatellites for The Aerospace Corporation, one called Sensate by a group of ham radio enthusiasts in the Washington DC area, and three built by students at Santa Clara University in California. The Aerospace Corporation picosatellite, which was powered by primary batteries, proved to be very successful. To have a picosatellite that could successfully charge

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batteries would require having solar cells on all sides. Since I had a number of GaAs cells, I laid a number of these out on the table and measured what size would be required to have 8 of these cells. This area was about 3.5 inches square. I decided it would be worthwhile to have satellites in a launcher that were not required to be locked down during launch, since if the clearance was 0.010 inches, this distance would not cause any undo accelerations during ELV launches. Thus, a distance of 0.250 was allowed for each rail capturing the corners of the satellites. This then made the width of the picosatellite 4”. Upon looking for a box that could be used for a model for the picosatellite, a 4” cubic plastic box was found at Tap Plastics in Mountain View, California. This box is normally used for Beanie Baby displays. The thought was to develop a launcher similar to the one that was used in OPAL but for a 4” cube. To keep the pusher foot, the door and other cubes from touching the solar panels on the ends, it was decided to add a ¼ inch small cube on each corner, since these were available at Tap Plastics. This “pusher feet” then protected the ends of the cube. At that time JPL and Lockheed Martin had a Mars Lander failure, which was found to be caused by a one party using English units and the other using metric units. In poking some minor fun at this error, it was decided to make the cube in metric units. Since 10cm was very close to 4”, it was designed to be a 10cm cube. This then led to a 10 x 10 x 10 cm cube with 1000 cubic centimeters, which filled with water, would weigh 1kg (the designated upper limit of a picosat weight) A plastic model of the launcher was then made for three cubes and had a spring pusher foot and door. The cube model and the launcher were taken to Cal Poly in the summer of 1999 and shown to Prof. Jordi Puig-Suari to get assistance in developing the launcher. The concept of having a standard for a picosatellite and a launcher that could be used by many universities could lead to a large number of picosatellites being launched at one time from several launcher tubes. If one party handled the launcher interface with the launch provider, then it seemed possible to get launches for university programs that could be affordable (less than $50,000). This concept was shown at the JUSTSAP conference in Hawaii in November 1999. At that time it was given the name S^3Sat for Student Space Science Satellite. After returning from Hawaii a web page was developed for S^3Sat. But after numerous times of typing S^3Sat, in December 1999 it was decide to make the typing of the name easier and call it CubeSat. So from a Beanie Baby box, a new picosatellite was developed that seems to have turned into an international standard. The present standard CubeSat and the launcher developed by Cal Poly are shown in Figure 5.

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Figure 5. Concept of Picosatellite and Launcher POD

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