- SLS: NASA identifies DAC-1 configuration candidates for wind tunnel tests

With infrastructure testing for SLS (Space Launch System) rocket architecture set to take place at the Kennedy Space Center, Florida this month, configuration reviews for the rocket itself are proceeding on course, with NASA selecting five SLS configurations for wind tunnel testing in the 140 mt, 95 mt, and 70 mt payload-to-orbit ranges.

The basics:

As assessments continue for the baseline architecture that will be the Space Launch System, better known as SLS, rocket, NASA has completed a review that has identified the nine leading configuration candidates for the SLS rocket.

As stated in the DAC-1 (Design Analysis Cycle) Analytical Configurations of Interest presentation, available for download on L2, “Based on manifest there are potentially 9 configurations for analysis (combinations of Outer Mold Lines, numbers/type boosters, numbers of engines).”

In all, the analysis team identified five configurations to proceed to wind tunnel testing.

“Bounding analysis will be conducted based on wind tunnel data and booster/engine configurations for conservative performance and environments,” notes that the DAC-1 presentation.

In particular, the question of the exact axial and bending loads that will be transmitted to the CS (core stage) and SS (second stage) in the Orion Multi-Purpose Crew Vehicle (MPCV) plus Payload configuration are under consideration.

Furthermore, the initial DAC 1 presentation notes that the “SS fitted configurations will only fly with the Advanced Boosters,” whereas SLS rocket variations without SS could fly with regular twin five segment Solid Rocket Boosters (metal casings with a PBAN propellant).

The MPCV plus DCSS configurations will only be allowed to fly with twin five segment PBAN SRBs.

The 140 mt configurations:

The first configuration to gain mention for wind tunnel testing is the proposed 140 mt class LEO cargo launch configuration for SLS – which is nearly identical to the LEO crew launch vehicle with the only real differences being the width of the segments delivered into Low Earth Orbit (LEO), the fact that one would carry crew and one would carry cargo, and the height of the vehicles.

For the cargo only vehicle, the width of the segment delivered to LEO would be 33 feet and the entire rocket height would be 376.2 feet. For the crew configuration, the width of the segment delivered to LEO would be 27.6 feet and the total height of the vehicle would be 388.6 feet.

Particularly, two configurations for this 140 mt class LEO launch vehicle were presented – one configuration using two 5 segment SRBs and one using two liquid fueled boosters.

The SRB Configuration:

For the SRB configuration, the presentation notes that the core stage of the SLS rocket would have five RS-25E liquid fueled engines and an upper stage utilizing two J-2X-288 engines.

Each five segment SRB in this case would be made from a Graphite/Epoxy casing material and would be expendable, meaning it would not be recovered after the launch of the vehicle.

A HTPB propellant would be used for each SRB for a total of 4,121,074 lbf in a vacuum per second and a total burn time of 98.7 seconds.

During this 98.7 second burn time, the twin SRBs would operate in tandem with the core stage of the SLS rocket. This core stage would utilize five RS-25E engines operating at 111 percent of rated power. The engines themselves would consume a total of 2,054,640 lbm of liquid oxygen and liquid hydrogen during the core stage burn.

The core stage burn would last 358.9 seconds with each of the five RS-25E engines producing 415,182 lbf at sea level and 521,950 lbf in a vacuum.

This vacuum level of trust from each of the five engines combined with the thrust from the twin SRBs would give this 140 mt class LEO rocket a total thrust in a vacuum of 10,851,898 lbf.

Following core stage burnout and separation, the second stage’s two J-2X-288 engines would ignite and fire at 100% for rated thrust at 288,000 lbf in a vacuum for each engine.

These two engines would burn for 358.9 seconds, consuming a nominal ascent propellant load of 469,677 lbm of liquid oxygen and liquid hydrogen.

With this configuration, the 140 mt class LEO launch vehicle would be able to deliver 305,178 lbm (or 138.4 mt) of payload into a 30×130 nmi orbit at an inclination of 29.0 degrees with an initial orbital insertion altitude of 86.9 nmi.

The Liquid Booster Configuration:

The second 140 mt class LEO rocket would fly in a configuration utilizing two 3 NHE-OC-100 engine liquid fueled boosters, a 5 RS-25E engine core stage, and a 2 J-2X-288 engine second stage.

In this configuration, each liquid fuel booster would contain 1,596,607 lbm of liquid oxygen and RP-1 propellant to be consumed by three NHE-OC-100 engines, each capable of producing 901,944 lbf at sea level and 1,000,000 lbf in a vacuum.

The three engines would be operated at 100% of rated performance and burn for 149.4 seconds.

Like the SRB design, the liquid fueled rocket boosters would work in tandem with the five core stage RS-25E engines.

The core stage, in this case, would have the exact same specifications in terms of engine thrust ratios, propellants and associated masses, and burn time as the core stage of the SRB rocket configuration.

In this scenario, the total thrust of the rocket during first stage flight would be 8,021,414 lbf, just over 2.8 million lbf less than the SRB configuration.

Likewise, the second stage for the liquid rocket booster configuration would be identical to the second stage configuration of the SRB rocket design.

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However, a key difference between the two rocket designs would be the amount of payload they could deliver into LEO.

Here, the liquid rocket booster configuration would win out over the SRB rocket configuration with an ability to lift 313,005 lbm (or 142.0 mt) of payload into a 30×130 nmi orbit at an inclination of 29.0 degrees with an initial orbital insertion altitude of 86.9 nmi.

The 95 mt configuration:

The 95 mt SLS rocket configuration – capable of carrying crew or cargo into a LEO – would utilize two PBAN five segment SRBs and a five RS-25E engine core stage. The rocket itself, in cargo configuration, would stand 298.9 feet tall. The crew version of the rocket would stand just over 300 feet tall.

Each SRB would be composed of steel case material, would be expendable, and would be fueled with a PBAN propellant. This would provide an initial 3,510,467 lbf in a vacuum of thrust per SRB, totaling 7,020,934 lbf with the two SRBs.

Total burn time for each SRB would be 128.4 seconds.

Moreover, the two SRBs would work in conjunction with the five engine core stage of the 95 mt SLS rocket.

This core stage would carry 2,045,814 lbm of liquid oxygen and liquid hydrogen. In turn, this propellant would power each RS-25E engine at 111 percent of rated performance for 360.5 seconds at an initial sea level thrust of 415,182 lbf and a vacuum thrust of 521,950 lbf per engine.

Total thrust of the core stage with the twin five segment Solid Rocket Boosters would be 9,630,684 lbf in a vacuum.

With no second stage, the total mass capable of being lifted into LEO with this configuration would be 205,530 lbm (or 93.2 mt) into an initial 30×130 nmi orbit at an inclination of 29.0 degrees with an orbital insertion altitude of 87.4 nmi.

The 70 mt version:

The fourth of five configurations selected for wind tunnel testing is the 298.9 foot tall 70 mt LEO version of SLS. This configuration would utilize two 5 segment PBAN SRBs and a three or four RS-25E engine core stage.

In this configuration, the SRBs would be identical to those of the 95 mt configuration.

The core stage, however, would utilize only three RS-25E engines. While each engine would burn at 111 percent of rated thrust and with the same thruster ratio as the RS-25E engines on the 95 mt version, the reduction from five engines to three engines would limit the initial thrust of the vehicle and the total amount of payload it could carry to orbit.

In all, the core stage for this configuration would burn for a total of 588.7 seconds.

The rocket itself would be capable of delivering 159,543 lbm (or 72.4 mt) of payload into an initial 30x 130 nmi orbit at an inclination of 29.0 degrees with an initial orbital insertion altitude of 87.3 nmi.

The fifth configuration is noted to be identical to the 70 mt version only with a crew capsule instead of cargo capsule.

(Images: Via L2 content, driven by L2′s new SLS specific L2 section, which includes, presentations, videos, graphics and internal updates on the SLS and HLV, available on no other site. Lead image via NASA.)

(L2 is – as it has been for the past several years – providing full exclusive SLS coverage, available no where else on the internet. To join L2, click here:

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