Author: Raymon Furth

Space-Based 3D Printing Tweaks ASEB's Interest

Space-Based 3D Printing Tweaks ASEB's Interest

Space-based additive manufacturing – better known as 3D printing – was one of many technologies discussed at Friday’s meeting of the National Research Council’s (NRC’s) Aeronautics and Space Engineering Board (ASEB).  Entry, Descent and Landing (EDL) technologies and solar electric propulsion were also on the agenda.

Additive manufacturing is a process where a product is built by assembling material, usually layer upon layer, from a 3D digital design.  Bhavya Lal of the Science and Technology Policy Institute presented an update to ASEB of an ongoing NRC study on space-based additive manufacturing of space hardware. Although it has gained headlines recently, additive manufacturing dates back to the 1980s when it was developed by industry and academia with the support of several federal agencies including the Office of Naval Research (ONR), the Defense Advanced Research Projects Agency (DARPA), and the National Science Foundation (NSF).

In response to a question, Lal expressed her personal observations that NASA and the Air Force are showing interest in the technology, but are operating on different timescales.  She explained that, at the moment, NASA appears to have a short term vision of the technology.  It is cooperating with the company Made in Space Inc. to launch an additive manufacturing system to the International Space Station (ISS) next year to assess its capabilities to print tools and spare parts.  The Air Force, however, has a more long term vision — to print a small spacecraft several decades from now. The NRC study, which is expected to be released in the early summer of 2014, will assess the current state of the technology and focus on the feasibility of space-based additive manufacturing and its possible implications 20 to 40 years from now.

Entry, Descent and Landing (EDL) technologies for landing a spacecraft on a planetary surface were the next topic at the ASEB meeting.  Jim Masciarelli of Ball Aerospace and Technology Corporation and Suraj Rawal of Lockheed Martin Space Systems explained that these technologies are used for a spacecraft entering the atmosphere of a planetary body at hypersonic velocities, descending and decelerating below supersonic velocities in the atmosphere, and landing on the surface. Each of these steps usually requires different technologies. The successful Curiosity rover’s landing on Mars used a rigid-body aeroshell to enter the atmosphere, supersonic parachutes to slow down, and a sky crane to lower the rover onto the surface. These technologies are limited to payload masses around one ton, while future payloads for a human expedition to the surface of Mars are likely to be about 40 tons.   Masciarelli told the ASEB that a deployable aeroshell with a large surface area may be a key technology for larger payloads as well as for slowing smaller vehicles through the supersonic stage of EDL. Rawal spoke on aerobraking, where a rigid-body aeroshell system skims the atmosphere on multiple passes to slow the vehicle down enough for landing.

ASEB also received an update from Alex Galimore, University of Michigan, and Roger Myers, Aerojet Rocketdyne, on solar-electric propulsion (SEP).  SEP is receiving increased attention as a technological centerpiece of NASA’s proposed Asteroid Redirect Mission (ARM).  SEP offers an advantage over chemical rockets by using its propellant mass more efficiently.  Propellant used in SEP is accelerated to more than five times the velocity of rocket propellant.  The drawback is that the amount of propellant mass being expelled by SEP at any given second is much smaller than in chemical propulsion systems.  This then requires more time to accelerate the spacecraft to the velocities needed for its mission. The advantage of using propellant more efficiently is that SEP systems can be less massive and have a smaller volume than chemical propulsion systems. Current challenges for producing more powerful SEP systems include lifetime testing, solar array technologies, power electronics, and thermal control. Gallimore mentioned that academic research in this field tends to be thruster specific, while Myers recommended that future research focus on electric propulsion’s power electronics and solar arrays.

Options for Military Satellite Communications Debated

Options for Military Satellite Communications Debated

The latest installment of the “A Day Without Space” series, sponsored by the George C. Marshall Institute and the TechAmerica Space Enterprise Council focused on the pressures felt by the Department of Defense (DOD) to ensure its military satellite communications (MILSATCOM) systems respond to demands for cost reduction, improved performance, and reduced vulnerabilities.

Thursday’s “The Future of MILSATCOM” panel discussion outlined the challenges MILSATCOM faces and strategies to address them using a new report by Todd Harrison of the Center for Strategic and Budgetary Assessments as its basis.

As the Obama Administration has been stressing for years, the space domain today is “contested, congested and competitive.”  More than 40 countries have space-based assets and more than 1,000 active satellites along with over 21,000 objects of man-made debris are being tracked in orbit.  This crowded region is being contested as countries develop technologies that challenge U.S. space capabilities, including China’s highly visible demonstration of an anti-satellite (ASAT) capability in 2007.

According to Harrison, the current threats to MILSATCOM systems can be divided into three groups.  The first group includes physical attacks on satellite constellations either by kinetic impactors, like China’s 2007 ASAT test, or directed energy attacks, such as high-powered lasers and microwave systems that can degrade or damage critical satellite components like solar arrays and sensors.   Another type of physical attack on MILSATCOM systems might not be directed at the satellites, but at their ground stations causing similar disruption in communications in a less expensive manner.

The second group of threats identified by Harrison is electronic attacks that can jam the capabilities to uplink or downlink data and commands between ground stations and satellites.  The third group is cyber-attacks.   Harrison said in his report that adversaries could  “gain access to a system to monitor the flow of data and discern sensitive operational details, such as location of users and which users are communicating with each other.” Another form of cyber-attack that could be more damaging mentioned in his report was “If an adversary were able to take control of a satellite, for example, it could shut down all communications, move the satellite to a different orbit, or even destroy the satellite by expending its fuel supply or damaging its electronics.”  Harrison concludes that the threats of most concern are an adversary gaining control of satellite systems, uplink jamming, and assaults on ground stations.

In order to address the challenges and threats of a more crowded and contested space domain Harrison states in his report that “The United States does not need space capabilities greater than its potential adversaries.  Rather the nation needs reliable, resilient space capabilities that enable other weapon systems to be superior to those of an adversary.”  To improve the reliability and resilience of U.S. space capabilities he made six recommendations.  

The first was to transition the MILSATCOM architecture from a two-tiered (protected and unprotected) to a three-tiered structure.  The highest tier, for strategic communications, would be largely unchanged with robust levels of protection from threats.  The lowest tier also would remain the same, providing unprotected services for non-essential communications on commercial satellites.  What Harrison proposes is a new middle-tier of systems that provide some level of protection to tactical users.  He explains in the report that “only 7 percent of the current architecture’s capacity is protected, meaning many tactical users are using unprotected systems for mission critical communications.”  Thus he wants tactical systems that have passive defenses against jamming, detection and interception.  This tier could include Advanced Extremely High Frequency (AEHF) payloads hosted on other military satellites, for example, he writes.

 Other recommendations included:

  • Inviting Pacific allies such as Japan, Australia, and South Korea to join MILSATCOM’s proposed middle tier to drive cost down and deter adversaries from attacking the partner nations’ satellite networks
  • Avoiding strategic cost traps such as an expensive shoot-back defense system to adversaries’ kinetic ASAT technology
  • Leveraging current programs to build and evolve new capabilities while avoiding the start of new and expensive programs
  • Implementing competition more efficiently to reduce redundancy and costs
  • Consolidating MILSATCOM programs, budgets, and operations under one Service — he recommended the Air Force

During the panel session that followed Harrison’s presentation, Greg Edelund, Director of Communication Systems at Northrop Grumman Aerospace Systems, emphasized that there is a synergy between resiliency and affordability.  He defined resiliency by addressing the differences between the costs of building defensive systems for MILSATCOM, whether passive systems like satellite hardening or active systems like “shoot-back” systems against kinetic ASAT capabilities, compared to the costs for adversaries to disrupt U.S. systems.

Asymmetric threats occur when adversaries can spend orders of magnitude less to disable or defeat a U.S. system than the U.S. system cost to build, Edelund explained.  Furthermore, he asserted that 95 percent of MILSATCOM systems are vulnerable to threats and that ground stations are the most vulnerable.  To address asymmetric threats, he proposed moving the battle to space by creating disaggregated MILSATCOM systems consisting of a large number of small satellites in various orbits that are capable of maneuvering and that can be quickly reconstituted.  Such an architecture would substantially increase the costs for an adversary to disable or destroy the system.

Justin Keller, Advanced Programs Director of Global Communications Systems at Lockheed Martin Space Systems Company, recommended that the United States look at possible threats up until 2030 and then choose the right package to handle the challenges and increase affordability. He disagreed with Harrison’s proposal to consolidate all MILSATCOM programs into the Air Force, stressing the effectiveness of the Navy’s existing MILSATCOM systems and arguing that transferring them into one Service would not be an improvement.

Marc Johansen, Vice President of Satellites & Intelligence Programs at Boeing, supported Harrison’s proposed restructuring of MILSATCOM systems into a three tiered system and mentioned that the Boeing 702 satellite production line is flexible across commercial and government program specifications.  He cited the Wideband Global SATCOM commercial-like follow-on vehicles as an example of efficiency.   He said they are experiencing 25 percent savings by reducing government involvement and oversight, which translated into about $150 million in savings over three satellites for the Air Force. He added that by transitioning them into a purely commercial acquisition approach by removing the remaining oversight and unique military specifications, the government could achieve 50 percent savings and operate in the lowest proposed tier.

Len Schiavone, Director of Technology for Integrated Communications Systems at Raytheon Space and Airborne Systems, elaborated on the difference between tactical and strategic mission communications.  Tactical mission communications must be protected against jamming, interception and detectability while strategic mission communications must be able to survive through nuclear blasts as well as have more stringent information security than tactical missions.   He agreed that satellite constellations be disaggregated and proposed that tactical mission communications be built with large capacities for data transfer at a more economic price. Those satellites would then be supported by lower capacity strategic mission communications which require a more expensive defensive package.

Editor’s Note: welcomes Raymon Furth as a new correspondent.  Furth is an astronomy student at the University of Colorado-Boulder.  He is currently serving in an internship position in Washington, DC supporting the Assistant Vice President of Research and Federal Relations with the University of Colorado Office of Government Relations.  Read more about him on our “About Us” page.  (Note:  We have clarified Furth’s internship title.)