Near Future for Vastly Increasing Space Capabilities – SpiderFab and Spacex

1. Spiderfab can reduce costs by ten times or more and enable vastly larger structure in space. Larger structures such multi-kilometer solar sales, antennas or mirrors can transform space capabilities.

In March, 2014, NASA awarded Tethers Unlimited, Inc. (TUI) a $750,000 contract to continue development of its “Trusselator” technology. The Trusselator is a device for in-­space additive manufacture of high-­performance truss structures for systems such as large solar arrays and antennas.

Tethers Unlimited is developing a set of technologies called SpiderFab to enable on-­orbit fabrication of spacecraft components. The SpiderFab architecture integrates elements of 3D printing, automated composite layup, and robotic assembly to create large, light-weight structures. The SpiderFab robotic systems will integrate these structures with solar cells, reflectors, and other elements to create football-­stadium sized antennas, multi-­hundred kilowatt solar arrays, and other large components for space systems.

NASA has given a phase 2 NIAC contract to Tethers Unlimited. The NIAC contract is for developing techniques to enable robotic systems to assemble these trusses into larger structures, such as antenna dishes and solar arrays

Technical Abstract

The Trusselator technology will enable on-orbit fabrication of support structures for high-power solar arrays and large antennas, achieving order-of-magnitude improvements in packing efficiency and launch mass while reducing life-cycle cost. The Phase I Trusselator effort successfully demonstrated fabrication of continuous lengths of high-performance carbon fiber truss using a novel additive manufacturing process, establishing the technology at TRL-4. The initial truss samples displayed bending stiffness efficiency superior to SOA deployable mast technologies. The Phase II effort will address the key technical risks and mature the Trusselator technology to TRL-6. We will do so by first refining the additive manufacturing process elements to improve process reliability and increase structural performance of the truss products. We will then design and prototype a Trusselator capable of operation in the thermal-vacuum environment of space, incorporating design improvements to reduce weight and stowed volume. Demonstration of fabrication of multi-meter lengths of truss in a vacuum environment will establish the technology at TRL-6. We will also develop an automated process for integrating the fabricated truss with thin-film solar cell blankets, and demonstrate this process with a solar cell blanket simulator. These Phase II efforts will prepare the Trusselator for flight demonstration in Phase III efforts to enable its adoption into the critical path for flight missions requiring high-power solar arrays.

Potential NASA Commercial Applications

The Trusselator is a key element of the NIAC “SpiderFab” architecture for on-orbit fabrication and integration of space systems. This technology will enable order-of-magnitude improvements in performance-per-cost for a wide range of mission, including:

* High Power Solar Arrays for SEP Exploration Missions
* Multi-Hundred-Meter Solar Sails for Outer Planet Missions
* Arecibo-scale Antennas for High-Bandwidth Communications with Mars and Deep-Space Missions
* Kilometer-Scale Masts for Long-Baseline Interferometric Astronomy
* Kilometer-Scale Sparse Apertures for Exoplanet Imaging

Potential Non-NASA Applications
The Trusselator will also enable on-orbit fabrication of large apertures and baselines for DoD space systems to enable order-of-magnitude improvements in bandwidth, sensitivity, resolution, and power for a wide range of tactical, strategic, and national security missions, including SATCOM, geolocation, SIGINT, and Earth observation. It will also enable affordable construction of large antennas for GEO commercial communications satellites.

2. Spacex will attempt to land the first stage of Falcon 9 on December 9th, 2014. Being able to land and reuse rocket boosters can reduce the costs for launching into space by ten to one hundred times.

3. The first launch of the Falcon Heavy should be in 2015.

As of March 2013, Falcon 9 v1.1 launch prices are $4,109 per kilogram ($1,864/lb) to low-Earth orbit when the launch vehicle is transporting its maximum cargo weight.

As of March 2013, Falcon Heavy launch prices are below $1,000 per pound ($2,200/kg) to low-Earth orbit when the launch vehicle is transporting its maximum delivered cargo weight. SpaceX has claimed the cost of reaching low Earth orbit can be as low as US$1,000 per pound if an annual rate of four launches can be sustained, and as of 2011 planned to eventually launch 10 Falcon Heavy and 10 Falcon 9 annually.

The first commercial launch of a Falcon Heavy is targeted for 2017.

4. Spacex is developing the methane Raptor engine.

This would enable monster rockets and would likely be the BFR (Big F**ing Rocket) or Mars Colony Transport. Elon Musk has discussed getting the cost of space launch without reuse down to $500 per pound with a large rocket.

Exoscientist Robert Clark has calculated a 15 Raptor engine Spacex rocket could enable abut 500 tons of payload in a single launch.

A June 2014 talk by Tom Mueller, the head of rocket engine development at SpaceX, provided more specific engine performance target specifications indicating 6,900 kN (705 tonnes-force) of sea-level thrust, 8,200 kN (840 tonnes-force) of vacuum thrust, and a specific impulse of 380 seconds.

The Spacex Falcon heavy has three cores and has nine engines on each core as seen in this picture from the Spacex.com site. Having five engines per core would show about three engines in profile on each core.

Pictures of the Falcon Heavy engines from Spacex.

In April 2014, SpaceX completed the requisite upgrades and maintenance to the Stennis test stand to prepare for testing of Raptor components, and expected to begin tests at the facility prior to the end of May 2014.

The Raptor engine will be powered by liquid methane and liquid oxygen using a more efficient staged combustion cycle, a departure from the ‘open cycle’ gas generator system and lox/kerosene propellants that current Merlin engines use. The Space Shuttle Main Engines (SSME) also used a staged combustion process, as do several Russian rocket engines.

More specifically, Raptor will utilize a “full-flow” staged combustion cycle, where 100 percent of the oxidizer—with a low-fuel ratio—will power the oxygen turbine pump, and 100 percent of the fuel—with a low-oxygen ratio—will power the methane turbine pump. Both streams—oxidizer and fuel—will be completely in the gas phase before they enter the combustion chamber. Prior to 2014, only two full-flow staged combustion rocket engines have ever progressed sufficiently to be tested on test stands: the Soviet RD-270 project in the 1960s and the Aerojet Rocketdyne Integrated powerhead demonstration project in the mid-2000s.

Raptor is being designed to produce 8,200 kN (1,800,000 lbf) of vacuum thrust—6,900 kN (1,600,000 lbf) thrust at lift-off—with a vacuum Isp of 380 seconds and a sea-level Isp of 321 seconds. Final thrust and Isp specifications for the as-built engines are expected to be refined as SpaceX moves the engine through the multi-year development cycle.

Additional characteristics of the full-flow design that are projected to further increase performance or reliability include:

* eliminating the fuel-oxidizer turbine interseal, which is a potential point of failure in more traditional engine designs
* lower pressures are required through the pumping system, increasing life span and further reducing risk of catastrophic failure
* ability to increase the combustion chamber pressure, thereby either increasing overall performance, or “by using cooler gases, providing the same performance as a standard staged combustion engine but with much less stress on materials, thus significantly reducing material fatigue or [engine] weight.”

5. An orbital propellant depot is a cache of propellant that is placed in orbit around Earth or another body to allow spacecraft or the transfer stage of the spacecraft to be fueled in space. It is one type of space resource depots that have been proposed for enabling infrastructure-based exploration

Intelsat has recently contracted for an initial demonstration mission to refuel several satellites in geosynchronous orbit, beginning in 2015.

NASA had plans to mature techniques for enabling and enhancing space flights that use propellant depots in the “CRYOGENIC Propellant STorage And Transfer (CRYOSTAT) Mission”. The CRYOSTAT vehicle was expected to be launched to LEO in 2015.

Cryostat does not appear to be in the 2015 NASA budget summary.

The CRYOSTAT architecture comprises technologies in the following categories:

Storage of Cryogenic Propellants
Cryogenic Fluid Transfer
Instrumentation
Automated Rendezvous and Docking (AR&D)
Cryogenic Based Propulsion

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