NASA has announced a significant change to its agreement with Sierra Space for cargo missions to the International Space Station (ISS). The agency stated it is "no longer obligated" to order resupply flights using the company's Dream Chaser spaceplane, a decision stemming from persistent development delays that have pushed back the vehicle's debut.
The original contract, awarded in 2016 under the Commercial Resupply Services 2 (CRS-2) program, included a minimum of seven cargo missions for Sierra Space. While this modification removes the mandatory order, the door remains open for future flights if the Dream Chaser successfully completes a critical flight demonstration.
Key Takeaways
- NASA has removed its obligation to order a minimum of seven ISS resupply missions from Sierra Space.
- The decision is a direct result of multi-year delays in the development of the Dream Chaser spaceplane.
- Sierra Space can still receive mission orders from NASA, but only after a successful demonstration flight of the vehicle.
- This contract adjustment highlights the challenges of developing new space hardware and affects NASA's logistics planning for the ISS.
Contract Modification Details
NASA's statement clarifies a pivotal shift in its Commercial Resupply Services 2 (CRS-2) contract. The agency's decision to remove the guaranteed minimum mission order for Sierra Space introduces new performance-based conditions for the aerospace company.
Originally, Sierra Space was one of three companies, alongside SpaceX and Northrop Grumman, selected to provide cargo transport to the ISS. The CRS-2 contracts were designed to ensure a steady and reliable supply chain for the orbiting laboratory, fostering competition and redundancy among providers.
According to a NASA spokesperson, the contract was structured to accommodate development timelines, but the extended delays have necessitated this adjustment. The change effectively transforms Sierra Space's guaranteed missions into potential future orders, contingent on the vehicle proving its capabilities.
"Our primary goal is to ensure the safety and operational readiness of the International Space Station. While we support the development of innovative new vehicles like Dream Chaser, we must adapt our procurement strategy to meet the station's logistical needs reliably," a NASA official commented on the decision.
The Dream Chaser Spaceplane
The Dream Chaser is a unique vehicle in the current landscape of space transportation. Unlike the capsule-based designs of SpaceX's Dragon and Northrop Grumman's Cygnus, Dream Chaser is a lifting-body spaceplane designed to land on a conventional runway.
This design offers several distinct advantages that made it an attractive option for NASA.
- Gentle Re-entry: The spaceplane experiences much lower gravitational forces during re-entry, around 1.5 Gs, compared to the higher G-forces of capsule landings. This is ideal for transporting delicate scientific experiments and sensitive hardware back to Earth.
- Rapid Access to Cargo: Landing on a runway allows for immediate access to the cargo upon touchdown, which is critical for time-sensitive biological research and other experiments.
- Reusable Design: The vehicle is designed for high reusability, which is intended to lower launch costs over the long term.
Background on the CRS-2 Program
NASA's Commercial Resupply Services (CRS) program is a cornerstone of its ISS operations. Initiated to outsource cargo delivery to private companies, the program's second phase (CRS-2) began with contract awards in 2016. The goal was to create a competitive marketplace for ISS logistics, reducing reliance on any single provider and driving down costs. SpaceX and Northrop Grumman have been flying regular missions under this program for years.
A History of Delays
The path to the launchpad for Dream Chaser has been longer than anticipated. When Sierra Space won the CRS-2 contract in 2016, the first flight was projected for 2019. However, the program has faced a series of technical hurdles and schedule revisions common in the development of complex new spacecraft.
Development challenges have reportedly involved various systems, from propulsion components to software integration and thermal protection systems. Each delay has had a cascading effect, pushing back critical milestones like integration with its launch vehicle, the United Launch Alliance (ULA) Vulcan Centaur rocket.
The Vulcan rocket has also experienced its own development delays, which has further complicated the timeline for Dream Chaser's inaugural mission, named Tenacity. This interdependence between the launch vehicle and the payload is a common factor in modern spaceflight scheduling.
ISS Cargo Requirements
The International Space Station requires a constant flow of supplies to support its crew of seven astronauts and the hundreds of scientific experiments conducted onboard. Each year, commercial cargo missions deliver over 20,000 kilograms (44,000 pounds) of food, water, equipment, and research materials.
The Path Forward for Sierra Space
Despite the contract modification, Sierra Space's Dream Chaser program is not canceled. The focus now shifts entirely to the vehicle's upcoming demonstration mission. This uncrewed flight will be a comprehensive test of all systems.
Key Milestones for the Demo Mission
- Launch: The Dream Chaser will launch atop a ULA Vulcan Centaur rocket from Cape Canaveral Space Force Station.
- ISS Rendezvous and Docking: The spaceplane must autonomously navigate to the ISS and successfully dock with the station.
- Cargo Operations: While docked, it will need to demonstrate the transfer of cargo to and from the station.
- Undocking, Re-entry, and Landing: The most critical phase involves undocking, performing a de-orbit burn, surviving atmospheric re-entry, and landing safely on the runway at the Kennedy Space Center.
A successful demonstration would prove the vehicle's readiness and allow NASA to begin placing mission orders. Sierra Space remains confident in its vehicle's capabilities and is focused on completing the final stages of testing before its first flight.
For NASA, this decision underscores a pragmatic approach to managing its complex supply chain. By retaining SpaceX and Northrop Grumman as active providers, the agency ensures the ISS remains fully supplied while allowing innovative but delayed programs like Dream Chaser the time to mature without jeopardizing core operations. The future of the spaceplane in NASA's resupply architecture now rests on its performance in its first flight.
