[Note: this is a blog post version of a whitepaper we recently sent out describing the technical idea that is at the heart of the Altius business plan I pitched at the 2011 NewSpace Business Plan Competition.]
A key missing capability that is needed to enable commercially competitive research and development on space stations like the ISS is the ability to send and receive short lead-time just-in-time packages. The current long lead-times for space station deliveries make it challenging for station researchers and manufacturers to compete commercially with terrestrial counterparts. While many companies are currently developing small rockets capable of lifting payloads of the right size class to low-earth orbit (LEO), this does not serve the critical space station user need for just-in-time deliveries because these vehicles lack the capabilities needed to safely approach the station by themselves. Specialized delivery vehicles like Progress or ATV possess the capabilities needed to safely approach the station, but they cannot be affordably scaled down to the size that these small rockets can lift while leaving any useful payload. Altius Space Machines is developing a solution for this missing capability called the Direct to Station (D2S™) delivery system, which will enable small launch vehicles to safely deliver just-in-time cargo directly to the ISS, without the need for separate, proximity-operations-capable delivery vehicles.
D2S Technical Description
The Altius D2S delivery solution has two principal subsystems: a station-based guidance and control system, and an extremely-long, station-based Sticky Boom™ capture mechanism. Sticky Boom uses a compliant electroadhesive gripper that can adapt itself to the geometry of any space object and then adhere to its surface, regardless of surface material, using controlled electrostatic forces. This gripper is mounted on the end of an extremely long deployable and steerable articulated boom, which is capable of matching speeds with visiting objects over a much wider range of relative velocities than traditional robotic arms.
As shown below, (1) as a rocket upper stage approaches the station exclusion area, (2) the D2S guidance and control system tracks and performs relative navigation for the incoming rocket stage, and then (3) sends the stage thruster commands enabling the stage to use its own propulsion systems to approach close enough for (4) the D2S Sticky Boom to capture it and reel the payload in to the station. By offloading the fine-control positioning to the electromechanically articulated boom, the coarse-control capabilities of the rocket upper stage become adequate for its portion of the task.
Illustration of D2S Concept of Operations
Additional Applications of D2S
Large-Scale Direct to Station Deliveries: D2S can also be scaled-up to handle deliveries from EELV-class launch vehicles such as Atlas V, Delta IV, or Falcon 9. With the Space Shuttle now retired, D2S can reinstate the capability of delivering large replacement parts or expansion modules using existing launch vehicles without requiring the development of space tugs or the installation of expensive proximity-operations upgrades to the EELV upper stages.
Propellant Depot Resupply: The same techniques can also be used to simplify the delivery of propellant in simple, passive containers to future propellant depots, or enable the integration of large space exploration vehicles in LEO before departure to deep-space destinations.
Nanosat/Microsat Launch Anchor Market: By enabling steady demand for space station deliveries by nano- and micro-scale launch vehicles, D2S can provide an anchor market for these launch systems. This market is potentially bigger than the current small satellite launch market increasing the potential for several healthy launch providers in this payload class.
Vehicle Return Assist: The D2S hardware can also simplify the departure of sample return vehicles. By releasing the return vehicle far below the station, with a slight amount of backward velocity, the vehicle enters a trajectory that will never re-intersect with ISS. This can greatly reduce or eliminate proximity-operation requirements for such vehicles.
D2S Departure Assistance Illustration
- Develop relationships with relevant NASA groups to promote understanding of D2S.
- Work with ISS Visiting Vehicles Group to determine the best way to implement D2S to ensure safety while minimizing the overhead placed on visiting nanosat and EELV upper stages.
- Work with station researchers and manufacturers to better understand their logistics needs
- Interface with Nanosat Launch Vehicle developers to ensure their vehicles are designed from the outset to be D2S compatible.
- Work with partner companies to analyze flight dynamics, and determine Sticky Boom system design requirements.
- Develop Sticky Boom hardware including an arbitrary-geometry-capable gripper and an extremely long-reaching storable articulated boom crane system based on NASA technology.
- Space qualify and flight test the D2S system including abort operations
- Develop standard procedures for qualifying new upper stages for D2S delivery
- Work with ISS National Lab to remove any other obstacles to short lead-time deliveries.