New Mission Concepts for SLS With Use of Large Upper Stage

Boeing recently released a proposal for a new upper stage for the SLS Block I configuration, that would enable the launch of even heavier payloads to deep-space destinations. Image Credit: NASA
Boeing recently released a proposal for a new upper stage for the SLS Block I configuration that would enable the launch of even heavier payloads to deep-space destinations. Image Credit: NASA

Boeing recently released a set of proposals for new missions beyond low-Earth orbit for NASA’s Space Launch System, or SLS, utilising a newly designed Upper Stage.

The SLS is NASA’s next generation heavy-lift launch vehicle (HLV), which is on schedule to make its inaugural unmanned test flight in 2017. It will be used for launching the Orion Multi-Purpose Crew Vehicle, or MPCV, the space agency’s next manned spacecraft currently under construction, to deep-space destinations such as the Moon and Mars—a capability that had been lost with the cancellation of the Apollo lunar missions more than 40 years ago.

An artist rendering of the various configurations of NASA's Space Launch System. Image Caption/Credit: NASA
An artist rendering of the various configurations of NASA’s Space Launch System. Image Caption/Credit: NASA

Although the first two launches of the SLS in 2017 and 2021 respectively are designed to be test flights of the initial Block I configuration capable of delivering 70 metric tons to low-Earth orbit (LEO), NASA is designing the heavy launch system to be evolvable, with the final Block II configuration having a payload capacity of 130 metric tons to LEO—rivaling the capability of the Saturn V rocket that sent humans to the Moon during the 1960s and ’70s.

As reported at the NASA website, Boeing, which is the prime contractor for designing and building the SLS’s core and upper stages, recently presented its proposal for a new Large Upper Stage, or LUS, for use on the SLS, which would enable new missions to low-Earth orbit and beyond.

The currently designed upper stage for the Block I version of SLS is an Interim Cryogenic Propulsion Stage (ICPS), also known as the Delta Cryogenic Second Stage, or DCSS. This is the same upper stage used on the Delta IV rocket, and it employs a single RL-10B2 engine developed by Pratt & Whitney. Although the ICPS would boost a 70-metric-ton payload to LEO in the SLS Block I version, Boeing’s proposal for the LUS would significantly advance this capability to more than 90 metric tons, allowing for even more ambitious deep-space missions. “A new 8.4m Large Upper Stage (LUS), as a follow on to the interim Cryogenic Propulsion Stage (ICPS), can provide significant increases in SLS payload injection capability,” notes the company in its presentation.

An alternate concept of placing a human outpost to the Earth-Moon L2 point with the SLS is Skylab II, proposed by a team of engineers working with the Advanced Concepts Office at NASA's Marshall Space Flight Center. Image Credit: NASA
An alternate concept of placing a human outpost to the Earth-Moon L2 point with the SLS is Skylab II, proposed by a team of engineers working with the Advanced Concepts Office at NASA’s Marshall Space Flight Center. Image Credit: NASA

“Someone reminded me that, up until the last two modules were put up on the ISS (via Shuttle), Skylab had more crew volume,” says Jim Crocker, Vice President and General Manager, Civil Space, Lockheed Martin Space Systems Co. “Skylab was done with one Saturn V. Sometimes it requires re-thinking of what you’re doing.”

These new mission concepts studied by Boeing fall into four main categories: LEO destinations, cislunar and lunar missions, Mars and Outer Solar System destinations.

One of the payloads that could take advantage of the SLS’s LEO payload capability, according to the Boeing study, is Bigelow Aerospace’s proposed BA 2100 inflatable habitat. Bigelow Aerospace is best known for its innovative and ambitious work on designing and launching inflatable modules in orbit, based on NASA’s TransHab technology. The private company has already launched two experimental modules in low-Earth orbit, Genesis I and II in 2006 and 2007 respectively. It is already planning to send a Bigelow Expandable Activity Module, or BEAM, on the International Space Station in 2015 and plans to develop  the first privately built space station called Bigelow Commercial Space Station, constructed from several BA 330 modules that are currently under development.

The large Bigelow BA 2100 module, could fit inside the 8.4m payload fairing of the proposed LUS upper stage. Image Credit:
The large Bigelow BA 2100 module could fit inside the 8.4m payload fairing of the proposed LUS upper stage. Image Credit:

Yet the company revealed even more ambitious plans in the 2010 International Symposium for Private and Commercial Spaceflight held in Las Cruces, N.M., with the unveiling of the BA 2100, or Olympus module concept. As the number on its name implies, BA 2100 would feature a living area of 2,100 cubic meters of volume, completely dwarfing the smaller BA 330. This enormous habitat would have a calculated mass of 70 to 100 metric tons, making the SLS the only heavy-lift vehicle capable of placing it into orbit. That fact was acknowledged by Bigelow Aerospace Vice President Jay Ingham as well. “If a super-heavy-lift launch vehicle ever did exist, probably in the range of around 100 metric tons, would require an 8-meter fairing to launch the BA-2100,” Ingham discussed during the Symposium.

“SLS allows delivery of the BA-2100 via direct insertion to a low earth orbit and is the only launch vehicle capable of delivering a payload this large to LEO,” notes Boeing in its LUS concept presentation. Besides being used as a space hotel complex or space science research laboratory in low-Earth orbit, the BA 2100 could also be used as a large self-sufficient crew habitat for long interplanetary missions to Mars or anywhere else in the Solar System.

The main purpose of the SLS is to enable beyond-Earth orbit human space exploration. In 2011 Boeing proposed a design for a cislunar Exploration Gateway Platform, located in the L1 or L2 Lagrangian points of the Earth-Moon system. This mission concept envisioned the use of existing left-over hardware from the ISS program for the construction of a cislunar manned outpost that would enable regular access to cislunar space and the lunar surface itself. Many within the space agency view this concept as the next logical step beyond low-Earth orbit for human exploration, serving as a testing ground for long-duration missions prior to a human trip to Mars. “Building a translunar outpost is an important first step in retrieving an asteroid, returning to the moon or venturing to Mars. Using the SLS/LUS would allow the Exploration Platform to be constructed and crewed in only two launches, as opposed to the four missions required using SLS/ICPS (interim Cryogenic Propulsion Stage), thus saving cost and significantly shortening the time required to start accruing the benefits of a crewed Exploration Platform in translunar space,” notes the new Boeing study.

Boeing's proposal for an Exploration Gateway Platform, at a Lagrandgian point in the Earth-Moon system. Image Credit: Boeing/NASA
Boeing’s proposal for an Exploration Gateway Platform, at a Lagrangian point in the Earth-Moon system. Image Credit: Boeing/NASA
A mockup of the proposed Bigelow BA 2100 inflatable module. With a projected payload mass between 70 to 100 metric tones, the only launch vehicle existing or under development that could place it to orbit, is the SLS. Image Credit: Bigelow Aerospace
A mockup of the proposed Bigelow BA 2100 inflatable module. With a projected payload mass between 70 to 100 metric tons, the only launch vehicle existing or under development that could place it to orbit is the SLS. Image Credit: Bigelow Aerospace

Besides human space exploration, the LUS could greatly advance robotic exploration as well, with its ability to directly send large interplanetary spacecraft to their destinations to the outer Solar System, mitigating the need for multiple gravity-assist manuevers that greatly prolong the mission duration to many years or decades.

The Interim Cryogenic Propulsion Stage currently designed for the SLS Block I version uses a 5m payload fairing that is capable of sending approximately 3 metric tons of payload to Jupiter, 1.8 tons to Saturn, and just 0.13 tons to Uranus. The proposed LUS upper stage, featuring an 8.4m payload fairing, would be capable of sending three to four times more massive payloads to these destinations. Depending on the LUS variant being used (having a single, dual, or 4-engine configuration), the new upper stage could directly send a payload of approximately 8.5 metric tons to Jupiter, 6 tons to Saturn, and 2 tons to Uranus. This payload capability would enable new and exciting missions to Europa, Titan, Enceladus, and Uranus that just aren’t possible with existing launch vehicles today. “The SLS provides a critical heavy-lift launch capability enabling diverse deep space missions,” states the Boeing report. “The added payload to destination that can be provided by a new Large Upper Stage, would be an enhancement for future science, astronomy, and Human spaceflight missions.”

The 4-engine configuration of Boeing's proposed Large Upper Stage for the SLS. Image Credit:
The 4-engine configuration of Boeing’s proposed Large Upper Stage for the SLS. Image Credit:

The new SLS/LUS lift capability would enable a Europa orbiter or lander to reach the Jovian moon in approximately three years after launch, and a similar mission could reach Titan in four. “Imagine the science return with SLS, where we can get there within a few years, and how that can accelerate scientific discovery,” says Crocker. “We don’t know what we’re going to find in science, but we do know that if you find it sooner, you get a much higher science return for your investment.”

A dedicated Uranus orbiter has also been the longing of the planetary science community. A Uranus orbiter is listed as the third highest priority Flagship mission after Mars and Europa in the 2013-2022 U.S. Planetary Science Decadal Survey. Dr. Mark Hofstadter, a planetary scientist at NASA’s Jet Propulsion Laboratory, stressed that point during a presentation at the January 2013 meeting of the Outer Planets Assessment Group, in Atlanta, Ga. “The Group is concerned that no action was taken on its findings last year regarding a Uranus mission study,” notes Hofstadter in the presentation, “and again urges that NASA initiate such a study responsive to Decadal Survey science goals for the ice giants.”

The 8m primary mirror version of the proposed ATLAST space telescope. Image Credit: NASA, MSFC Advanced Concepts Office
The 8m primary mirror version of the proposed ATLAST space telescope. Image Credit: NASA, MSFC Advanced Concepts Office

Planetary exploration wouldn’t be the only field in space science that could benefit from the use of the SLS/LUS concept. The new upper stage would also be able to lift the proposed Advanced Technology Large Aperture Space Telescope, or ATLAST, that is under consideration by NASA. ATLAST is a next generation space telescope, featuring a monolithic 8m primary mirror, four times bigger than the one on the Hubble Space Telescope. An alternative design also calls for a 16m segmented primary mirror, which could also fit inside the bigger LUS payload fairing. According to the Space Telescope Science Institute’s project website, “ATLAST will have an angular resolution that is 5 – 10 times better than the James Webb Space Telescope and a sensitivity limit that is up to 2000 times better than the Hubble Space Telescope … It is envisioned as a flagship mission of the 2025 – 2035 period, designed to address one of the most compelling questions of our time. Is there life else where in our Galaxy? It will accomplish this by detecting ‘biosignatures’ (such as molecular oxygen, ozone, water, and methane) in the spectra of terrestrial exoplanets.”

Maybe the most important aspect of the LUS design is its cost-saving approach to the SLS’s development. If chosen by NASA, the LUS would be constructed at the agency’s Vertical Weld Center at Michoud Assembly Facility in New Orleans, where Boeing already will be constructing the SLS’s Core Stage, without the need for extra welding or other machining equipment, thus helping to further bring the SLS’s development costs down.

Video Credit: NASA/Marshall Space Flight Center

Since its inception in 2011, the SLS has been heavily criticised by many within the space community for its perceived lack of missions. During her recent appearance on a radio talk show, former NASA Deputy Administrator Lori Garver heavily criticised SLS as being a rocket to nowhere.“Where is it going to go?” she asked during the show. Although Boeing’s LUS upper stage concept hasn’t been yet approved by NASA, it nevertheless largely invalidates Garver’s criticism by showcasing that the space agency’s newest heavy-lift vehicle could be used for all shorts of exciting and ambitious human and robotic missions throughout the Solar System.


The article is based in part on the opinions of the author that do not necessarily represent those of  AmericaSpace.

Want to keep up-to-date with all things space? Be sure to “Like” AmericaSpace on Facebook and follow us on Twitter: @AmericaSpace


  1. SLS is the next logical and much-needed step in providing multi-purpose flight capabilities. As expertly outlined in Leonidas’s article, such a booster propels human beings further into our cosmic backyard with both manned and robotic missions that will unlock the mysteries of the Jovian moons and beyond. In looking at the image at the top of the article, I am reminded of an issue of National Geographic (circa 1960) that showed models of the Saturn family of boosters along with the “Nova” that boasted 12 million pounds of thrust, standing some 400+ feet tall. It was impressive display and here we are, some 50+ years later realizing that those early concepts were not that far-fetched after all! Proceed with the development expeditiously and allow us the capabilities to insure our leadership role in space exploration.

    • You’re right Tom. In more than one respect, the SLS is continuing from where the Saturn V left off.

      It’s interesting to note that if all goes as planned and the SLS will make its first unmanned test flight in 2017, it will be exactly 50 years since the first unmanned test flight of the Saturn V in 1967. Let’s hope that the US doesn’t repeat the same mistake of building a whole cislunar transportation system and then throw it in the dustbin, like it did with Saturn/Apollo.

  2. It irritates me that so much hot air is expended about the SLS being a vehicle with no destination, when your article demonstrates that it actually carries the potential to unlock the outer Solar System. Uranus has always had a strong pull for me, ever since I watched Voyager 2’s flyby in January 1986 as a 9-year-old boy. The political will needs to be there, just as the scientific and visionary will is already there. Let us hope that the SLS (or at least its technology) will reach fruition, for in spite of its faults and imperfections and vast cost, it is necessary for some kind of major investment to get NASA out of low-Earth orbit for the first time in 5 decades. Great article.

    • You’re completely right Ben! If you want to make ambitious space exploration and expand into the Solar System and especially to reach the outer planets, you need the public space program to lead the way. And there’s no cheap – at least not with the current means of getting to orbit, which is rocket propulsion technology. And as long as programs for heavy-lift vehicles keep going forward, despite all the political turmoil, hope can spring eternal…

  3. Leonidas, thank you very much for what is without question one of the finest articles I have read about our Space Launch System. The potential of this new vehicle is amazing, and promises to open the solar system to human exploration as never before thought possible. The only downside is that the average human lifespan is not two hundred years so that the heroic trailblazers of the space age like Gagarin, Shepard, et al. could see what their efforts have wrought. There will not be immediate “profit” from such exploration, as there is none from Curiosity as it explores its way across Mars, Cassini as it analyzes the surface of Titan, or New Horizons as it streaks towards Pluto. Imagine a bona fide commercial venture approaching Wall Street financial analysts seeking investment in a Mars rover that will take images of the planet, blast rocks with a laser, examine the soil, but not return anything to be sold for profit. What investment firm would give a “buy” rating to a “private sector” spacecraft that will measure the depth of a methane ocean on Titan, but not generate a dime of return on investment? Some things, absent corporate welfare, government must do. Cancelling the SLS and giving taxpayer dollars to a corporation to do the same thing would do nothing but add a layer of expense in the form of executive salary, bonus, stock option, expense account, etc. The Space Launch System/Orion is not just another weapon system or social program. It is the means to a giant step in human evolution. It will forever change the course of human history. This is an enormous undertaking that will be very expensive, perhaps even more than the 0.48 of a penny of every budget dollar now received by NASA. It’s amusing that former NASA Deputy Administrator Lori Garver says, “Where is it going to go?” (Although it is a cause for concern that someone who holds such sentiments was supposed to be working to advance SLS/Orion while at NASA.) SLS/Orion will go where we have the will to take it. As to the expense? In 1867 the proposal to spend a vast amount of money, seven million dollars, to purchase Alaska from Russia for two cents per acre was ridiculed as outrageous, an expenditure of money that just isn’t available given the economy, an enormous waste of taxpayer dollars, and Seward’s Folly. Golly, maybe Russia would be willing to buy back Alaska today for seven million dollars.

  4. The SLS is a huge waste of taxpayer money! SpaceX could do this without costing the taxpayers anything!! They like, already launched some rockets into low Earth orbit all by themselves! No help from NASA, those rotten bureaucrats!

    Ah hell, who am I kidding…I don’t believe any of that…Excellent article as always.

    • Thank you for reminding me about those magnificent plans and designs of the engineers in the ’60s, Jeff!

      Indeed, private industry accessing LEO while NASA goes beyond, is the goal. if the private space sector works more closely with the government and not against it, there’s nothing that cannot be done in space. That’s something that many people in the space community should start to acknowledge.

India Successfully Launches Trouble-Plagued GSLV on First Orbital Mission of 2014

SpaceX Ready to Launch Thaicom-6 Satellite Tonight After Three-Day Delay