NASA has released a Request For Information for a new engine the agency will use on the Orion European Service Module beginning with EM-6 (Exploration Mission 6). The Request For Information states that the engine is needed by mid-2024 in order to support the EM-6 flight of the Space Launch System, which under the currently in effect budget and operational timeline for NASA will be No Earlier Than 2027.

Orion Service Module engine RFI:

As part of NASA’s plan to utilize as much hardware that remained at the end of the Space Shuttle program as possible for the SLS (Space Launch System) rocket and Orion capsule, the agency mandated that Orion’s European Service Module (ESM) utilize the leftover Space Shuttle Orbital Maneuvering System (OMS) engines for the first five Orion/ESM flights.

The supply of available Shuttle OMS engines will run out after EM-5, currently slated for No Earlier Than 2026, as the European Service Module is expended at the end of each flight and not reused. As such, NASA requires a replacement engine beginning with EM-6, and the agency took the first step toward that replacement yesterday in releasing a Request For Information (RFI) to the aerospace industry.

“NASA invites industry to submit a response to this Request For Information to assist NASA in planning for the development of a new Service Module Main Engine for the Orion Multi-Purpose Crew Vehicle.”

All RFI responses are due by 16 March 2018 to the Johnson Space Center in Houston, Texas, and according to the RFI document, “are intended to provide input for an assessment of a new engine for the ESM with respect to the constraining performance and interface requirements.

“NASA desires a low cost replacement engine to minimize program cost and schedule impacts to the Orion vehicle. The replacement engine shall minimize development time for an engine and reduce manufacturing/production costs while still meeting NASA programmatic, technical, design, construction, and workmanship approaches and standards for human rating.”

However, because the Orion ESM has been designed to use the leftover Shuttle OMS engines, the needed replacement engine must meet strict and already determined operational constraints and a host of other already-determined requirements.

Thus, NASA’s RFI is a way to ensure the agency is following the best practices possible to keep the cost of the new engine down while still meeting all safety and timeline requirements.

Constraining parameters:

Based on the current Shuttle OMS engine parameters, NASA’s RFI for the new service module engine states that the engine must have a minimum specific impulse (ISP) of 310 seconds using already established Standard Inlet Conditions.

According to the RFI, those Standard Inlet Conditions include a fuel inlet pressure of 244 psia, an oxidizer inlet pressure of 240 psia, and a propellant temperature of 70℉.

The engine must also be able to produce roughly 6,000 lbf of steady-state thrust in a vacuum with an engine thrust roughness “less than +5% of average steady state thrust.”

Moreover, the engine must reach 90% of steady-state thrust within 0.45 seconds (+/- 0.1 seconds) of receiving the “on” command while also not exceeding a peek overthrust of 150% of the mean steady-state thrust upon engine start.

The new engine must also use an oxidizer to fuel mixture ratio of 1.65 (+/- 0.03), carry a maximum weight of “~284 lbf” and a length of roughly 79 inches (with a max “head end to gimbal” length of 23 inches).

The current Shuttle OMS engine “gimbal to nozzle exit” length of 56 inches can be varied on the new engine, and the RFI specifically notes that if such a variance is suggested that the RFI answering company provide insight as to why.

Additionally, the engine must be able to gimbal greater than +/- 6 degrees in pitch and yaw during operation, must not exceed a maximum power consumption of 309 W, must be able to restart as soon as 240 seconds after its previous shutdown, and must be capable of supporting a mission duration of a minimum of 21 days for lunar missions and 210 days of “quiescent duration in cislunar or transit conditions.”

But the engine’s space-base and operational requirements aren’t the only points of information requested by NASA. The agency also released a set of requirements for the engine’s ground support, control of catastrophic hazards requirements, failure detection for crew safety requirements, independent confirmation of failure assessments, and reliability.

Specifically, NASA requested information on the ground handling elements for the engine, including installation, checkout, loading, cleaning, installation in Europe, testing in Europe and the United States, testing at various NASA centers/facilities, as well as launch preparations.

In terms of catastrophic hazards, the new ESM engine “shall provide failure tolerance to catastrophic hazards with no less than single failure tolerance except for areas approved by NASA or designed for minimum risk, zero failure tolerance, or integrated hazard controls.” Additionally, the engine must be able to detect failures that “could result in a catastrophic or critical hazard.”

Importantly, the engine must have a strong reliability potential and confidence level for two types of missions. For crewed lunar orbit flights, the engine must have a reliability of success probability of 99.8% and a minimum confidence level of 95%. For lunar sortie missions, the engine must have a reliability of success probability of 99.7% and a similar minimum confidence level of 95%.

Given the already above established requirements, the RFI released by NASA listed several requested response topics, including but not limited to engine assembly configuration conceptual design, performance, and capabilities; engine life cycle design maturity and Technology Readiness Level assessments; development of long-term affordability considerations; funding and schedule profiles; and suggestions for potential cost-sharing opportunities between industry and government.

Importantly, the RFI is not a request for a company to bid to build the engine, nor is it a guarantee that NASA will use or give credit for any design changes implemented to the new ESM engine based on the information received through the RFI process.

“The specific objective of this RFI is to solicit information that may potentially enhance NASA’s planned approach for an OMS engine replacement, including engine subassembly, nozzle extension, and heat shield assembly, and assist in developing the acquisition strategy,” notes the RFI document.

Moreover, NASA’s RFI also states that “This RFI is not to be construed as a commitment by the Government nor will the Government pay for information solicited. NASA will use the information obtained as a result of this RFI on a non-attribution basis. The information received may be used in developing the best approach for fulfilling these requirements, and therefore, may be recognizable to the interested party.”