Student-Built Gossamer Spacecraft: Why Aren't There More (Yet)? Michael A. Swartwout* Washington University, St. Louis, MO, 63130

University-class spacecraft are defined as flight missions where the training of students in spacecraft engineering is as important as the “main” mission – or is the main mission itself. By the end of 2009, one hundred thirty university-class spacecraft will have been placed on rockets, with spacecraft ranging from 200 grams to nearly 200 kg. And, given the very constrained size of university-class missions, and the much higher risk tolerance of universities compared to industry, one would expect that gossamer systems would be an obvious candidate for flight experiments. Thus, it is perhaps a paradox that only 9 of those 130 missions have had gossamer systems – and seven have been on failed spacecraft. In this paper, we will review the history of university-class missions, highlighting the gossamer missions to date. We will use the data culled from these 130 missions to identify the main factor why there have been so few gossamer flights: the bifurcation in launch mass, type of experiment, and on-orbit failure rate between the government-charted “flagship” schools and the self-chartered “independent” schools. The schools most capable of flying successful gossamer experiments are the ones least in need of the benefits of gossamer systems. However, we will identify the changing external and internal trends that may lead to more gossamer flights in the near future.

I. Introduction

A

S of this publication date (30 March 2009), rockets have launched more than one hundred “university-class” spacecraft (i.e., spacecraft whose mission includes the training of university students in spacecraft engineering), including 50 launched in the past four years and an astonishing 21 more scheduled for the remainder of calendar 2009. The on-orbit success of these hundred missions has varied widely; a fifth were lost to launch failures, a fifth were deployed but failed almost immediately, while a quarter of the student satellites were operational for at least three years. Mission utility also varies greatly, with roughly one-third serving as Amateur radio communications relays, a third with science or technology demonstration missions, and a third with only an educational mission. For this paper, we broadly define gossamer systems as deployable structures with length scales greater than the launch dimensions of the spacecraft. While this definition seems excessively permissive – practically every professional spacecraft with deployable solar arrays would fit this “gossamer” label – and seems to ignore key points (i.e., low mass and low stiffness), this definition is appropriate for university-class missions. Given their very small mass, any objects deploying from a university-class spacecraft will necessarily be lightweight. And, since every university-class mission to date has used body-mounted solar arrays (or no arrays at all), a large deployable array would be worth noting. With respect to gossamer systems, there have been paradoxically-few student-built missions flown to date – eight, to be exact. We say “paradoxically” both because student-built spacecraft (especially the 1-kg CubeSat class) would greatly benefit from the added aperture for communications and power and because student programs are uniquely poised to fly high-risk technology demonstrations. Why, then, have there been so few? To answer those questions, this paper draws upon launch records, published reports and project communications to create a statistical examination of these student-built spacecraft, identifying correlations between reliability, size and the types of schools building space hardware. We have identified two broad categories of schools building flight hardware: flagship schools and independent schools. We define a flagship university as one designated by its government as a national center for spacecraft engineering research and development. Thus, by definition, flagships enjoy financial sponsorship, access to facilities and launch opportunities that the independent schools do not. There

*

Assistant Professor, Mechanical, Aerospace & Structural Engineering, Campus Box 1185, AIAA Senior Member. 1 American Institute of Aeronautics and Astronautics

is a growing disparity in both launch rates and mission success between the two classes; generally speaking, flagship schools build bigger satellites with more “useful” payloads, and tend to have sustained programs with multiple launches over many years. By contrast, the satellites built by independent schools are three times more likely to fail, and for most of these programs, their first-ever spacecraft in orbit is also their last, i.e., the financial, administrative and student resources that were gathered together to built the first satellite are not available for the second. The distinction between flagship and independent schools at least partly explains the lack of gossamer missions – the schools that are most capable of flying gossamer missions (flagships) are least inclined to do so; they typically have external customers and the resources to meet their mission goals without gossamer systems. But as will be shown, the circumstances are changing whereby technically-relevant gossamer missions may become more common. Before we can proceed, we must first clearly define what we mean by a university-class satellite, which we will also call student-built. This specification is needed because the “student” label has been applied to $15 million NASA science missions and 3-kg Sputnik re-creations. For the purposes of this discussion, a university-class satellite has these features:1 1) It is a functional spacecraft, rather than a payload instrument or component. To fit the definition, the device must operate in space with its own independent means of communications and command. However, self-contained objects that are attached to other vehicles are allowed under this definition (e.g. PCSat-2, Pehuensat-1). 2) Untrained personnel (students) performed a significant fraction of key design decisions, integration & testing activities, and flight operations. 3) The training of these people was as important as (if not more important) the nominal “mission” of the spacecraft itself. Therefore, a university-class satellite is defined by programmatic constraints and is different than a space mission with strong university participation. The purpose of university-class missions is to train students in the design, integration and operation of spacecraft, and this is accomplished by giving students direct control over the progress of the program. Many spacecraft with strong university connections do not fit this definition, especially those where the university contributes the primary payload. Similarly, while some spacecraft in the amateur radio service are university-class, many with the OSCAR designation do not fit the definition. Exclusion from the “university-class” category does not imply a lack of educational value on a project’s part; it simply indicates that other factors were more important than student education (e.g., schedule or on-orbit performance). A. Paper Overview We return to the question: why have there been so few university-class gossamer missions, and why would universities start building them now? In order to answer these questions, we will first review the history of university-class spacecraft from the first flight in 1981 through the present. From that review, we can observe the types of missions pursued, the types of universities participating, and prospects for success or failure on-orbit. Next, we examine the eight existing and two near-term gossamer missions. Given those observations, we will address that question, as well as a number of others about subsystem reliability, mission design and proper scoping of projects. B. Disclaimers This information was compiled from online sources, past conference proceedings and author interviews with students and faculty at many universities, as noted in the references. The opinions expressed in this paper reflect the author’s experience as both student project manager and faculty advisor to university-class projects. The author accepts sole responsibility for any factual (or interpretative) errors found in this paper.

II. A Brief History of University-class Satellites A list of university-class spacecraft launched from 1981 until the present is split between Tables 1 and 2, with the anticipated launch schedule for the remainder 2009 in Table 3. This table is an update to Ref 1, which did not include any of the 25 missions scheduled for 2009. The process for compiling this table was as follows: First, a list of all university-related small satellites that reached orbit (however low) was assembled from launch logs, conference proceedings (especially the AIAA/Utah State Conference on Small Satellites), the author’s knowledge and several satellite databases.1-5 Because of the difficulty in compiling and verifying information about the many student missions that were never launched, we have only included projects with a verifiable launch date. Furthermore, missions that did not meet our definition of “university-class” were removed from this list. 2 American Institute of Aeronautics and Astronautics

52 60 52 16 35 49 154 48 45 63 50 10 10 18 187 3 8 3 70 70 41 64 45 110 191 52 6 23 0.2 0.5 0.5 49 50 10 10 12 6 20 12 47 10 17 3 1 1 1 1 1 100 64

96 301 20 96 212 77 4 96 1 11 0 0.5 0.1 2 46 20 51 60 33 23 118 55 1.0 1.0 0.0 29 0 0 0 105 39 36 27 24 3 36 90 90 75 24 69 69 69 0 3 0 66 66

N S N N A N F N F N LF LF F N N N N N N N F N A N F F F N F F F A N N N N N N S A A N S S A F F F A A

S C T C C T C C T S C C C T E E T T S C T C S T T E E T E S S E S C C E S E C S C E S E E E E E T C

y y y y y y n y y n y n n y y n y y y n n y y y y y y y n n n y y y y y n y y y y y y y y y y n y y

Flag?

Multi

Type

UK UK USA USA Germany Korea France Korea Germany Germany Israel Mexico Mexico USA Europe Russia Germany Germany Israel USA USA South Africa Germany Korea USA USA USA USA USA USA USA China Malaysia Saudi Arabia Saudi Arabia Italy Sweden USA USA Germany Saudi Arabia Italy USA Japan Japan Canada Denmark Denmark Korea Russia

Status

University of Surrey University of Surrey Weber State, Utah State University Weber State Technical University of Berlin Korean Advanced Institute of Science and Technology CNES Amateurs (?) Korean Advanced Institute of Science and Technology Technical University of Berlin University of Bremen Technion Institute of Technology National University of Mexico National University of Mexico US Air Force Academy ESA/ESTEC-led partnership Russian high school students Technical University of Berlin Technical University of Berlin Technion Institute of Technology Naval Postgraduate School University of Alabama, Huntsville University of Stellenbosch Technical University of Berlin Korean Advanced Institute of Science and Technology Weber State, USAFA US Air Force Academy Arizona State University Stanford University Santa Clara University Santa Clara University Santa Clara University Tsinghua University ATSB King Abdulaziz City for Science & Technology King Abdulaziz City for Science & Technology University of Rome "La Sapienza" Umeå University / Luleå University of Technology Stanford, USNA, Washington University US Naval Academy Technical University of Berlin King Abdulaziz City for Science & Technology University of Rome "La Sapienza" Stanford University Tokyo Institute of Technology University of Tokyo University of Toronto University of Aalborg Technical University of Denmark Korean Advanced Institute of Science and Technology Mozhaisky military academy

Mission Duration (months)

UoSAT-1 (UO-9) UoSAT-2 (UO-11) NUSAT WeberSAT (WO-18) TUBSAT-A KITSAT-1 (KO-23) ARSENE KITSAT-2 (KO-25) TUBSAT-B BremSat Techsat 1-A UNAMSAT-A UNAMSAT-B (MO-30) Falcon Gold YES RS-17 TUBSAT-N TUBSAT-N1 Techsat 1-B (GO-32) PANSAT (PO-34) SEDSAT (SO-33) Sunsat (SO-35) DLR-TUBSAT KITSAT-3 JAWSAT (WO-39) Falconsat 1 ASUsat 1 (AO-37) Opal (OO-38) JAK Louise Thelma Tsinghua-1 TiungSAT-1 (MO-46) Saudisat 1A (SO-41) Saudisat 1B (SO-42) UNISAT 1 Munin Sapphire (NO-45) PCSat 1 (NO-44) Maroc-TUBSAT Saudisat 1C (SO-50) UNISAT 2 QuakeSat CUTE-1 (CO-55) XI-IV (CO-57) CanX-1 AAU Cubesat DTUsat STSAT-1 Mozhayets 4 (RS-22)

Mass (kg)

Nation

10/6/1981 3/1/1984 4/29/1985 1/22/1990 7/17/1991 8/10/1992 5/12/1993 10/26/1993 1/25/1994 3/2/1994 8/28/1995 8/28/1995 5/9/1996 10/25/1997 10/30/1997 11/3/1997 7/7/1998 7/7/1998 7/10/1998 10/30/1998 10/30/1998 2/23/1999 5/27/1999 5/27/1999 1/27/2000 1/27/2000 1/27/2000 1/27/2000 2/10/2000 2/12/2000 2/12/2000 6/28/2000 9/26/2000 9/26/2000 9/26/2000 9/26/2000 11/21/2000 9/30/2001 9/30/2001 10/12/2001 12/20/2002 12/20/2002 6/30/2003 6/30/2003 6/30/2003 6/30/2003 6/30/2003 6/30/2003 9/27/2003 9/27/2003

Primary School(s)

Launch Date

1 2 3 4 5 6 7 8 9 10 11 11 12 13 14 15 16 16 17 18 18 19 20 20 21 21 21 21 21 21 21 22 23 23 23 23 24 25 25 26 27 27 28 28 28 28 28 28 29 29

Mission

1981 1984 1985 1990 1991 1992 1993 1993 1994 1994 1995 1995 1996 1997 1997 1997 1998 1998 1998 1998 1998 1999 1999 1999 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2000 2001 2001 2001 2002 2002 2003 2003 2003 2003 2003 2003 2003 2003

Launch ID

Launch

Table 1. University-Class Spacecraft Launched From 1981 to 20031-5

NF NF NF NF F F NF F F NF F NF NF F NF NF F F F F NF F F F NF F NF NF NF NF NF F F F F F NF NF F F F F NF F F F NF NF F F

The remaining spacecraft were researched regarding mission duration, mass and mission categories, with information derived from published reports and project websites as indicated. A T-class (technology) mission flight-tests a component or subsystem that is new to the satellite industry (not just new to the university). An S– class (science) mission creates science data relevant to that particular field of study (including remote sensing). A C-class (communications) mission provides communications services to some part of the world (often in the Amateur radio service). While every university-class mission is by definition educational, those spacecraft listed as E-class (education) missions lack any of the other payloads and serve mainly to train students and improve the satellite-building capabilities of that particular school; typical E-class payloads are COTS imagers (low-resolution Earth imagery), on-board telemetry, and beacon communications. Finally, a spacecraft is indicated to have failed prematurely when its operational lifetime was significantly less than published reports predicted and/or if the university who created the spacecraft indicates that it failed. This list of spacecraft is complete to the best of the author’s research ability. For example, the listed launch masses should be considered approximate, as the variance in mass among different published records can reach as high as 50%. Similarly, values in the Mission Duration column are approximate; in the course of our research, we found some spacecraft that were known to have lost most or all of the primary payloads and communications equipment and yet were still listed as “operational”! In other cases, spacecraft that have greatly exceeded their 3 American Institute of Aeronautics and Astronautics

planned mission lifetime may be left idle or even abandoned by their primary operators, and thus the failure date of the vehicle is unknown.

2004 2004 2004 2004 2004 2004 2004 2005 2005 2005 2005 2005 2005 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2006 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2007 2008 2008 2008 2008 2008 2008 2009 2009 2009 2009

30 31 31 31 31 32 32 33 34 34 34 34 34 35 36 37 37 37 37 37 37 37 37 37 37 37 37 37 37 37 38 39 39 39 40 40 41 41 42 42 42 42 42 42 42 42 42 43 43 44 44 44 44 44 44 45 45 45 45

4/18/2004 6/29/2004 6/29/2004 6/29/2004 6/29/2004 12/21/2004 12/21/2004 8/3/2005 10/27/2005 10/27/2005 10/27/2005 10/27/2005 10/27/2005 2/21/2006 3/24/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 7/26/2006 9/22/2006 12/21/2006 12/21/2006 12/21/2006 1/10/2007 1/10/2007 3/9/2007 3/9/2007 4/17/2007 4/17/2007 4/17/2007 4/17/2007 4/17/2007 4/17/2007 4/17/2007 4/17/2007 4/17/2007 9/25/2007 9/25/2007 4/28/2008 4/28/2008 4/28/2008 4/28/2008 4/28/2008 4/28/2008 1/23/2009 1/23/2009 1/23/2009 1/23/2009

Naxing-1 (NS-1) Tsinghua University SaudiSat 2 King Abdulaziz City for Science & Technology SaudiComsat-1 King Abdulaziz City for Science & Technology SaudiComsat-2 King Abdulaziz City for Science & Technology UNISAT 3 University of Rome "La Sapienza" 3CS: Sparky ASU/NMSU/CU Boulder 3CS: Ralphie ASU/NMSU/CU Boulder PCSat 2 US Naval Academy XI-V (CO-58) University of Tokyo Mozhayets 5 Mozhaisky military academy UWE-1 University of Würzburg Ncube II Norwegian Universities SSETI Express (XO-53) European Universities CUTE-1.7 (CO-56) Tokyo Institute of Technology Falconsat 2 US Air Force Academy UNISAT 4 University of Rome "La Sapienza" Ncube Norwegian Universites KUTESat University of Kansas CP2 Cal Poly San Luis Obispo CP1 Cal Poly San Luis Obispo ION University of Illinois ICE CUBE1 Cornell University ICE CUBE2 Cornell University PiCPoT Politecnico di Torino, Italy SEEDS Nihon University SACRED University of Arizona Rincon University of Arizona MEROPE Montana State University HAUSAT-1 Hankuk Aviation University Baumanets 1 Bauman Moscow State Technical University HITSat (HO-59) Hokkaido Institute of Technology RAFT-1 US Naval Academy MARScom US Naval Academy ANDE US Naval Academy LAPAN-Tubsat Technical University of Berlin PEHUENSAT-1 (PO-63) National University of Comahue Falconsat 3 US Air Force Academy MidSTAR-1 US Naval Academy Saudi ComSat-3 King Abdulaziz City for Science & Technology Saudi ComSat-4 King Abdulaziz City for Science & Technology Saudi ComSat-5 King Abdulaziz City for Science & Technology Saudi ComSat-6 King Abdulaziz City for Science & Technology Saudi ComSat-7 King Abdulaziz City for Science & Technology CP4 Cal Poly San Luis Obispo CP3 Cal Poly San Luis Obispo Libertad-1 University of Sergio Arboleda CAPE-1 University of Louisiana YES2/Floyd ESA-led partnership Yes2/Fotino ESA-led partnership Cute 1.7 + APD II (CO-65)Tokyo Institute of Technology CanX 2 University of Toronto AAU-CubeSat II University of Aalborg SEEDS 2 (CO-66) Nihon University COMPASS 1 Fachhochschule Aachen Delfi-C3 (DO-64) Technical University of Delft SpriteSat (Raijin) Tohoku University PRISM University of Tokyo KKS 1 Tokyo Metropolitan College of Industrial Technology STARS 1 Kagawa University

China Saudi Arabia Saudi Arabia Saudi Arabia Italy USA USA USA Japan Russia Germany Norway Europe Japan USA Italy Norway USA USA USA USA USA USA Italy Japan USA USA USA S. Korea Russia Japan USA USA USA Germany Argentina USA USA Saudi Arabia Saudi Arabia Saudi Arabia Saudi Arabia Saudi Arabia USA USA Columbia USA Europe Europe Japan Canada Denmark Japan Germany Netherlands Japan Japan Japan Japan

25 15 12 12 12 16 16 12 1 64 1 1 62 10 20 12 1 1 1 1 2 1 1 2.5 1 1 1 1 1 92 2.7 1 1 75 56 6 54 120 12 12 12 12 12 1 1 1 1 30 6 2 2 1 1 1 3 50 8 3 8

59 57 57 57 57 13 41 0 1 0 0 1 5 5 27 12 27 3 25 25 23 23 23 23 23 5 5 1 5 0 0 11 11 11 11 11 11 0 2 0 0

A A A A A LF LF N S F F F F F LF LF LF LF LF LF LF LF LF LF LF LF LF LF LF LF N N A N A N A A A A A A A N N N N N F A A A A S S F A F F

T S C C T E E C E E E E C C S E E E E E T T T E E E E S E E C C C C C C S T C C C C C E E E E T T E T T E E T S T T T

y y y y y y y y y y y n y y y y n n y y n n n y n n n n n n n y y y y n y y y y y y y y y n n y y y y y n n n n y n n

Flag?

Multi

Type

Status

Mission Duration (months)

Mass (kg)

Nation

Primary School(s)

Mission

Launch Date

Launch ID

Launch

Table 2. University-Class Spacecraft, 2004-present1-5

F F F F F NF NF F F F NF NF NF F F F NF NF NF NF NF NF NF NF NF NF NF NF F F NF F F F F NF F F F F F F F NF NF NF NF NF NF F F NF NF NF F NF F NF NF

A. Past Gossamer Missions Only four university-class missions with gossamer systems were launched before 2008; three of those were merely 1-2 m long deployable gravity gradient booms (NCUBE 1, NCUBE 2, and ASUSat-1). The fourth mission, YES2, involved deployment of a 2-km tether. It should also be noted that NCUBE 2 was lost to a launcher failure, NCUBE 1 was never heard from on-orbit, and ASUSat-16,7 had a solar panel connectivity problem and was lost after 18 hours. The YES2 mission did successfully deploy its boom, but a rate damping miscalculation caused the tipmass payload to be ejected at the wrong velocity and the spacecraft was lost.8.9 4 American Institute of Aeronautics and Astronautics

Therefore, until 2009, what few examples we have of university-class gossamer missions were plagued by bad luck as well as the technical challenges that come with deploying large, flexible structures.

38 4 4 1 1 1 1 1 80 30 1 1 1 1 1 1 1 1 15 15 100

n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a

-

E T T E S T E E T T S T E T E S S E T T S

n y y y n y n y y n n y n n n n y n n n y

Flag?

Multi

Type

India Malaysia Malaysia Germany Switzerland Germany Turkey USA South Africa Russia Italy Italy Romania Poland France Switzerland Italy Spain USA USA USA

Status

Anna University ATSB ATSB University of Würzburg Ecole Polytechnique Fédérale de Lausanne Technical University of Berlin Istanbul Technical University Cal Poly San Luis Obispo University of Stellenbosch Ufa State Aviation Technical University Trieste University Politecnico di Torino, Italy University of Bucharest Warsaw University of Technology University of Montpellier II Ecole Polytechnique Fédérale de Lausanne University of Rome "La Sapienza" University of Vigo University of Texas University of Texas US Air Force Academy

Mission Duration (months)

ANUSAT InnoSat CubeSAT UWE-2 SwissCube-1 BeeSat ITU-pSat CP6 SumbandilaSat UGATUSAT AtmoCube e-st@r Goliat PW-Sat 1 ROBUSTA SwissCube-2 UNICubeSat XaTcobeo FASTRAC-A FASTRAC-B FalconSat-5

Mass (kg)

Nation

4/7/2009 4/21/2009 4/21/2009 4/25/2009 4/25/2009 4/25/2009 4/25/2009 5/5/2009 5/15/2009 5/15/2009 11/30/2009 11/30/2009 11/30/2009 11/30/2009 11/30/2009 11/30/2009 11/30/2009 11/30/2009 12/31/2009 12/31/2009 12/31/2009

Primary School(s)

Launch Date

46 47 47 48 48 48 48 49 50 50 51 51 51 51 51 51 51 51 52 52 52

Mission

2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009 2009

Launch ID

Launch

Table 3. Announced University-Class Launches, 20094

F F F NF F F F NF F F NF NF F NF NF F F NF NF NF F

C. Active Gossamer Missions The launch of the Japanese H-2A rocket in January 2009 doubled the number of student gossamer missions in orbit. Two more missions (SpriteSat and KKS-1) made use of gravity-gradient booms of a few meters in length and the STARS-1 mission uses a short tether with functional spacecraft on both ends.10 Unfortunately, the success rate of these schools is the same as the previous flight; as of this writing, none of these three missions are successfully operating; SpriteSat had a processor lockup after deploying the boom, STARS-1 has not deployed its tether, and KSS-1 has communication problems. While it is still early in the mission for these three, and it is still possible that they will recover these spacecraft, for the moment, all three must be regarded as in-flight failures.11 We can draw conclusions about the performance of the fourth gossamer experiment on that Japanese launch; the University of Tokyo’s PRISM spacecraft12 extends its optics using a 1-meter boom; the operations team has released “before and after” images verifying the release of the boom and its effect on the images generated. From the images, it is clear that the boom has deployed. D. Near-Term Gossamer Missions One additional true gossamer mission is planned for 2009; Warsaw University of Technology’s PW-Sat 1 will deploy a solar-sail-like membrane to significantly increase the atmospheric drag on the spacecraft, thereby reducing its orbital lifetime. This is the most ambitious gossamer mission to date, and, if successful, would mark a significant milestone in university-class gossamer systems. In particular, this mission would address one of the primary objections to CubeSats: the proliferation of orbital debris.

III. Observations Closer examination of Tables 1-3 reveals several important characteristics of university-class missions. We refer back to Ref 1 for detailed discussions of many classifications (e.g., mission lifetime, the relative success of flagships and independents in building sustained flight programs, and the types of missions flown by each kind of school). For this paper, we will highlight those most relevant to gossamer experiments. A. Number of Spacecraft and Size As one simply examines the number of spacecraft manifested per year since 1981 (Figure 1), it becomes obvious that the number of university-class missions has sharply increased this decade. From recent trends, it appears that 15-20 manifests/year has become the norm (contrasted with 24 manifests total over the first 19 years of universityclass flights). The other obvious trend is the downward march of spacecraft mass (Figure 2); whereas there were 8 spacecraft with mass under 10kg from 1981-2000 (and the first appearing in 1997), 18 of the 25 scheduled for launch in 2009 are under 10 kg. 5 American Institute of Aeronautics and Astronautics

The he decrease in the size of spacecraft makes gossamer systems more attractive – or even essential,, as the surface area of CubeSat-class class missions missio requires deployable structures for even modest power generation and antenna gain. The increase in the number of missions indicates that there are more opportunities for gossamer systems to fly. However, as will ill be shown, there are other factors precluding the adoption of gossamer systems. B. Two Classes of Universities As noted above, there is a significant difference in the number and nature of missions flown by independent and flagship programs. In general, as shown Figure 1. Number of manifested university university-class spacecraft by year in Figure 3, flagship schools are much more likely to have sustained programs (i.e., 2 or more different missions on different flights) than independents. Of the 23 flagship schools, more than half (14) are repeats – and 8 of the not-yet-repeated repeated launched their ffirst mission in the past 3 years,, which means many of them may become repeats. By contrast, only 9 of 40 independent schools have repeat launches, and four of these repeat programs are no longer sustained (having not launched anything for more than 8 years). Secondly, as shown in Figure 4, flagships are much more likely to fly “real real” missions (especially T-class and S-class) class), only a quarter of them have been E-Class Class (16 of 68). And the vast majority of the EClass flagship missions came from sustained programs that followed up with “real” missions. Nearly half of all independent missions (29 of 62) are E EClass. Finally, flagships tend to build larger spacecraft (47 of 68 have been largerr than 10 kg), while independents build smaller spacecraft (42 of 62 are under 10 kg). In combination, those trends indicate that flagships are most likely ely to fly gossamer experiments, since the same schools build more spacecraft and fly more “real” payloads. And yet flagships don don’t Figure 2. Spacecraft mass by year need gossamer systems, as they tend to build larger spacecraft. C. Failures As noted in the Tables, 22 university university-class missions have failed on-orbit. orbit. Of those 22, we can identify that 9 were lost to a combination tion of power and communication problems problems,, two had CPU lockup problems, one each were lost to radiation, ation, launch interface failure failure, and excessive cold on launch. Eight of the he 22 spacecraft were never heard from, and thus the failure source cannot be identified. And, of the 51 flagship spacecraft that have reached orbit (i.e., not counting rocket failures and missions not yet launched), only 5 have ve failed (10%). Conversely, of the 38 independent missions to reach orbit, 17 have failed ((45%). Finally, as noted in Section n II, 7 of 8 gossamer missions m to date have failed, though most of those failures do not appear to be a direct result of the gossamer systems themselves. 6 American Institute of Aeronautics and Astronautics

Again, we not the sobering so trend: independent schools have flown most of the gossamer missions, but independent schools have the higher failure rate.

IV. Conclusions Combining observations, we conclude that the schools most capable of flying gossamer missions are the flagships: their spacecraft tend to be larger (providing room for the gossamer deployment systems) and more reliable, and the flagship schools tend to build more spacecraft raft (providing institutional experience needed to design & implement a riskier/complex Figure 3. Comparison of repeat launches by flagship sta status gossamer system). system) However, the very nature of a flagship program makes such schools less likely to adopt gossamer systems, precisely because they are less tolerant to the perceived risk of adopting new technologies. Government sponsors tend to place mission usefulness and mission success above the introduction oduction of new technologies; the signi significantly-lower failure rate among ng flagships appears to prove out this philosophy. Still, there is reason to believe that these trends are shifting shifting. First, the sheer number of new independent schools and the need to increase aperture on CubeSats is likely to push these new programs toward towardss gossamer systems. systems While such a trend has not yet emerged, the deployable drag sail on PW PW-Sat Sat 1 is an important technology demonstration for mitigating the orbital debris concerns from all of these new, very small spacecraft. Finally, as government funding ing for gossamer systems decreases and the number of flight flight-hardware-capable capable university program increases, government sponsors could see university university-class spacecraft as a cost-effective effective way to flight-test their gossamer systems. The telescope on the University of Tokyo’s PRISM is a possible example of this idea. There is no doubt that university-class spacecraft would benefit from gossamer systems, especially for the CubeSat-class which is so constrained in available power and bandwidth. And yet, to get to the point where these technologies are flight-proven, we should anticipate a rash of in-flight failures among the independent schools that choose to test them. Alternately, if a flagship program were willing to add a gossamer experiment onto a larger spacecraft, it would speed the process of flight qualification. Figure 4. Mission type by year and university category

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References Most university-class spacecraft do not publish their work; this is further demonstration of the non-research aspects of their missions. Therefore, most information had to be collected from websites, especially from the Refs 2-5. 1

Swartwout, M., “The First One Hundred Student-Built Spacecraft”, IEEE Aerospace and Electronic Systems Magazine, Vol. 24, No. 3, 2009, pp. A1-A20. 2 SSTL, "Small Satellites Home Page," URL: http://centaur.sstl.co.uk/SSHP/micro/index.html, [Cited June 2007]. 3 SSTL, "Nanosatellites," URL: http://centaur.sstl.co.uk/SSHP/nano/index.html, [Cited June 2007]. 4 Krebs, G., "Gunter's Space Page," URL: http://www.skyrocket.de/space/space.html, [Cited 30 March 2009]. 5 AMSAT, " A Brief Chronology of Amateur Satellites," URL: http://www.amsat.org/amsat-new/satellites/history.php, [Cited 30 March 2009]. 6 Friedman, A., Underhill, B., Ferring, S., Lenz, C., Rademacher, J., and Reed, H., “Arizona State University Satellite 1 (ASUSat1): Low-cost, Student-Designed Nanosatellite," Journal of Spacecraft and Rockets, Vol. 39, No. 5, September/October 2002, pp. 740-748. 7 Rademacher, J., Reed, H. and Puig-Suari, J., “ASUSat 1: an Example of Low-Cost Nanosatellite Development,” Acta Astronautica, Vol. 39, No. 1-4, July/August, 1996, pp. 189-196. 8 Kruijff, M., van der Heide, E.J., Ockels, W.J., and Gill, E., “First Mission Results of the YES2 Tethered SpaceMail Experiment”, AIAA/AAS Astrodynamics Specialist Conference, Honolulu, Hawaii, 18-21 August 2008, AIAA-2008-7385. 9 Kruijff, M., van der Heide, E.J., “Qualification and in-flight demonstration of a European tether deployment system on YES2”, Acta Astronautica, Vol. 64, No. 9-10, May-June 2009, pp. 882-905. 10 Yamamoto, T., Yoshihara, H., Andatsu, A., Oohara, M., Ootani, M., Nohmi, M., “Development of Engineering Test Satellite STARS-I for Tethered Space Robot,” 25th International Symposium on Space Technology and Science, Kanazawa, Japan, June 4-11, 2006, 2006-s-04. 11 Tanaka, Y. and Sakurai, R., “Space: The final frontier of faulty technology”, The Ashi Shimbun, 31 March 2009, URL: http://www.asahi.com/english/Herald-asahi/TKY200903310053.html [Cited 31 March 2009]. 12 Nagai, M., et. al, “University of Tokyo’s Pico-Satellite Project ‘PRISM’”, 56th International Astronautical Congress, Fukuoka, Japan, Oct. 17-21, 2005, IAC-05-B5.4.09.

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