A final round of potential Heavy Lift Launch Vehicle (HLV) options – which will allow the NASA leadership to choose the design of the Space Launch System (SLS) as early as April, 2011 – has been created by The Human Exploration Framework Team (HEFT), which is coming to the end of its current architecture design phase.
HEFT2 and the SLS HLV:
The HEFT – tasked with providing decision support to NASA senior leadership for planning how the Human Space Flight (HSF) program will explore beyond LEO – are evaluating a set of options and forward paths via wide-ranging architecture options, including one of the focal points of NASA’s space flight future, the HLV – otherwise known as the Space Launch System (SLS).
The HEFT are tasked with evaluating a viable path which reaches out as far as 2028 and potentially beyond, working with NASA’s administration and steering councils, whilst providing a number of key recommendations to the NASA leadership.
One of their opening findings earlier this year dismissed large parts of the now defunct FY2011 proposal from President Obama, such as the recommendation to remove the initial requirement of a five year study of evaluating the design of the HLV. This finding continues to be a key recommendation several months later.
Click here for NASASpaceflight.com HLV- related news articles: http://www.nasaspaceflight.com/tag/hlv/
“Launch Vehicle Findings: An HLV is central to any robust human exploration program. Delaying a decision on HLV configuration and requirements to 2015 limits NASA’s options and hampers planning. There is no benefit to delaying work on the HLV, no technology needed for capability development,” noted one of the opening HEFT overview presentations (L2).
Support was also noted for a SD (Shuttle Derived) HLV, with the opening presentations (L2) showing preference for an inline Shuttle ET Diameter (27.5′) core, driven by Space Shuttle Main Engines (SSMEs) – utilizing existing RS-25D stock, prior to evolving to the less expensive (non-reusable) RS-25Es. This vehicle’s Upper Stage would be driven by RL10A4-3 engines.
“NASA will lose an opportunity to build from the existing flight-proven systems. Losing the capability to build an SSP (Space Shuttle Program)-derived HLV will require the development of new manufacturing, processing, and launch infrastructure at additional cost and schedule risk,” the HEFT presentation added in its opening recommendations.
“Recommendation: Accelerate the HLV decision – moderate HLV. Initiate a Shuttle-derived inline HLV Program beginning in FY2011. Initial 90 – 100 mt range. Defer human rating and upper stage to Block II.”
Those initial points provided a baseline as the HEFT transitioned into what is known simply as HEFT2, which refined the choices available for the future architecture by focusing on a trade-off between three strategies, which are also known and associated with Design Reference Mission (DRM) sets.
Strategy 1/DRM-1 (Technology development priority) evaluated the central elements of the President’s FY2011 budget proposal, to “seek game-changing capabilities that enhance how human missions can be conducted,” along with “five years of intensive development of advanced technologies before beginning development of human flight systems.”
“Reusability and Advanced Systems Development: Reusable spacecraft avoid repeated manufacture and launch for every mission. Advanced in-space propulsion (electric and chemical) minimizes the propellant needed in space,” outlined a late October presentation on the HEFT evaluations (L2).
Strategy 2/DRM-2 (Beyond Earth Orbit) focuses on “using human flights to inspire the public and aerospace workforce. Begin immediate development of flight systems.”
“Commercial & Refueling Emphasis. Reusable spacecraft avoid repeated manufacture and launch for every mission. Advanced in-space propulsion (electric and chemical) minimizes the propellant needed in space. Propellant purchased on orbit for beyond-LEO missions. Moderate-sized heavy-lift launch minimizes early development and recurring costs. Upper stage refueling in LEO.”
While Strategy 3/DRM-3 puts its weight behind the focal point of a HLV. “Heavy-Lift Emphasis: Early, large HLLV (in lieu of advanced technology development) focuses on eventual human exploration mission needs like Mars. Simple on-orbit “assembly,” direct launch of crew.”
Other options, named as DRM-4 and DRM-2A and 2B, combined or merged two of the strategies to create additional options. While HEFT are careful not to make too many assertions, the test architecture of visiting a Near Earth Orbit (NEO) cited issues with a commercial (such as the ULA master plan) and/or international cooperation approach (which even earned positive remarks in a previous Sidemount SD HLV presentation).
“Asteroid missions appear to stretch commercial launch capacity in ways that require more precise trades to validate,” added the presentation. “NASA might end up bearing the carrying cost of an expanded commercial launch infrastructure. Spreading the load among commercial and international suppliers might increase operations complexity, and a depot could incur additional NASA cost.”
What can be seen by HEFT’s approach is a level of consistency, as they now press forward to the end of the HEFT2 cycle by briefing NASA administrator Charlie Bolden on their findings next week. It is already known that Strategy 3/DRM-3 is the HEFT’s favored forward plan, and has since been renamed as the “capabilities-driven approach” as a result.
Focused around an architecture which incrementally develops new capabilities to allow NASA to go to multiple destinations, this path has a large amount of support from those involved with the evaluations, as was cited at an All-Hands at the Marshall Space Flight Center (MSFC) this week.
Led by MSFC director Robert Lightfoot, part of the All Hands meeting was devoted to discussion of the SLS status. Mr Lightfoot was joined by Todd May – who will become the SLS program manager, and Garry Lyles – who will become the SLS chief engineer, following NASA HQ’s decision to set up the SLS planning office at the Alabama center.
At the meeting it was noted that three RAC (Requirements Analysis Cycle) teams have been set up to study three potential SLS configurations, with a goal to derive vehicle-level designs which can meet NASA HQ requirements.
RAC-1 is studying an inline, LH2 core vehicle with Solid Rocket Boosters (SRB). While this vehicle is the previously noted SD HLV, the teams are avoiding such a name, given they are allowed to trade Space Shuttle Main Engines (SSMEs) with RS-68s, while also trading SRBs with Liquid Rocket Boosters (LRBs), in order to ensure they have the best configuration to battle with the other two HLV candidates.
RAC-2 is studying a Saturn V-type vehicle, utilizing an RP-1 first stage and LH2 second stage. Like RAC-1, the team is allowed to trade different engine options, within their designated configuration. UPDATE: Sources note SpaceX’s Falcon XX (huge vehicle with six Merlin 2 engines) is included the RAC-2 trades.
RAC-3 is studying vehicle designs based around several options, such as EELVs, with a large amount of latitude to study different tank sizes, including the evaluation of clusters of Atlas-sized tanks similar to how the Saturn IB first stage was built.
Key milestones will begin as early as next week, when the teams present preliminary results, ahead of a timeline which will wind up with final results sometime in mid-February of next year. At that point, MSFC will create a presentation of findings and recommendation for deliberations at NASA HQ.
Mr Lightfoot noted that NASA HQ alone will make the final decision on the vehicle configuration. This decision is expected in April, with Requests For Proposals (RFPs) expected to be published just a few weeks later, allowing for proposals to arrive in late summer, ultimately leading to contract(s) being awarded by the end of 2011.
The All Hands also noted that MSFC would be tasked a new goal, to manage affordability the way a development team would manage other technical measures such as mass or payload to orbit. That affordability drive is to be a key deciding factor, Mr Lightfoot noted.
This will be an important goal to achieve, as NASA await funding from a Continuing Resolution, one which provides the initial monies to press forward with the development of their new launch vehicle.
One problem to overcome may be the language of the CR, with the latest version – dated December 8 – citing the need for a HLV (SLS) capable of lifting 130 tons from the onset, as opposed to an often-preferred phased Block I and Block II approach.
“$1,800,000,000 shall be for the heavy lift launch vehicle system: Provided further, That the initial lift capability for the heavy lift launch vehicle system shall be not less than 130 tons and that the upper stage and other core elements shall be simultaneously developed,” notes the CR language.
It is likely that the HEFT and NASA HQ preference will focus on a HLV which is developed in two phases, opening with a vehicle capable of providing upmass assistance to the International Space Station (ISS) by 2016, in tandem with testing the vehicle’s early performance, prior to increasing its performance with an Upper Stage to the larger 130 ton target, in line with a timeline the missions requiring such a capability exist in NASA’s plans.
More information on the favored approach is likely to be forthcoming over the coming weeks, with HEFT2 officially completing its work on December 17, prior to handing over to a final phase – likely to be run out of NASA HQ – known as HEFT3.
(Images via NASA.gov, L2 presentations and Philip Metschan)