As NASA continues to mature a mission and support architecture path toward its much heralded endeavor of landing humans on Mars, the agency’s under-development heavy lift SLS rocket now stands to take on a primary space transportation role via a rapidly increasing flight rate designed to support human missions to Phobos by 2033 and to the surface of Mars by 2039.

Evolving toward Mars:

For over a decade, NASA has been hard at work developing the successor vehicle to the agency’s universally recognized Shuttle Orbiter fleet.

Initially, NASA aimed to transition from the Shuttle Program to the Constellation Program, which would have seen, at least at first, separate launch vehicles for crew (Ares I) and cargo (Ares V).

However, an Ares IV variant was under consideration in 2007 which would have combined the two launch vehicles into a single configuration.

Nonetheless, funding gaps, critical reports, and a political party change within the US government led to the downfall of the Constellation Program in early 2010 – rocket and Orion capsule in all.

A meeting in April 2010 subsequently modified outright cancellation of all aspects of the Constellation Program to keep the Orion crew module alive and under development – though its name officially changed from the Orion Crew Exploration Vehicle to the Multi-Purpose Crew Vehicle, with the initial omission of “Orion” from the name in an effort to distance the capsule from the Constellation Program.

“Orion” was later added back into the name, making it the Orion Multi-Purpose Crew Vehicle.

In September 2011, NASA subsequently announced the rocket architecture that would define its Space Launch System (SLS).

Despite bearing an Apollo-era paint scheme on the liquid fueled core stage to distance the rocket’s image from that of the Ares V and Ares IV architecture of the Constellation Program, the SLS is an initial blend of the two ideas – a Heavy Lift Vehicle (HLV) capable of launching just human missions, human missions and cargo, or just cargo missions to space.

Since 2011, NASA has continued to refine Orion, SLS, and the agency’s overall approach to what will be the seminal and most-famous mission of the 21st century: the landing of the first human beings on another planet.

This refined approach , while criticized by some, has seen NASA proceed through an intense, thought-out, and slow-moving study of numerous variables involving a multi-step, phased program to gain specific knowledge sets deemed necessary for human trips to the red planet.

But through all this, the number of SLS flights needed to undertake human missions to Mars was not discussed in earnest, and given the SLS’s slow introduction rate of three years between its first two flights, there has been growing concern as to SLS’s viability and flight rate.

Now, according to NASA’s “Evolvable Mars Campaign: Status Update to SLS Evolvability TIM” from 29 July 2015 (L2), not only have target dates for Phobos and Mars human missions been identified, but the needed flight rate and launch campaigns of the SLS to support such missions have also been identified.

SLS missions for Phobos by 2033 and Mars by 2039 and 2043:

According to the Status Update to SLS Evolvability TIM (Technical Interchange Meeting) presentation, available for download on L2, NASA hopes to place humans in the Martian system by the mid-2030s, with current reference points of crewed missions in 2033 to Phobos, in 2039 to Mars’ surface, and in 2043 for the second human Mars surface mission.

As noted by the presentation, “An SLS/Orion launch rate of one per year is sustainable in the Proving Ground.”

Importantly, this appears to be a specific reference to SLS’s initially slow flight rate.

Current planning documents have, for years, baselined SLS’s first mission, the uncrewed EM-1 flight, for 2017/2018, with EM-2, the first human mission of SLS and Orion, not occurring until at least 2021.

EM-3 had subsequently been mentioned as a notional mission occurring sometime thereafter, potentially not until 2023.

This slow rollout of a much heralded and anticipated HLV and crew capsule was worrisome not just from a debut standpoint but also from an unknown and uncertain launch market for SLS.

However, these concerns could prove to be for naught as NASA’s near-term Cis-lunar operations begin to take shape and long-range planning for human missions to the Martian system solidify – with current projections shown in the Evolvable Mars Campaign: Status Update to SLS Evolvability TIM presentation showing a total of 41 SLS flights from 2018 through 2046 to build-up to and support human Phobos and Mars surface missions.

Launch sequence to Mars:

In all, the Evolvable Mars Campaign presentation lays out a flight sequence for not just SLS but also for other EELVs (Evolved Expendable Launch Vehicles) and missions that will build toward the eventual 2033 human Phobos mission, 2039 human Mars surface mission, and 2043 follow-up Mars surface mission.

The start of that identified campaign, the EFT-1 flight of Orion, took place on 5 December 2014 and is set to be followed in 2016 by both the InSight Mars stationary lander and OSIRIS-REx asteroid sample return missions.

InSight and OSIRIS-REx are both slated to launch aboard Atlas V rockets from Vandenberg and Cape Canaveral Air Force Station, FL, in March and September 2016, respectively.

These robotic precursor missions would then be followed in 2018 with the debut of SLS – in its Block I, 70t configuration – on the uncrewed EM-1 circumlunar navigation test flight.

NASA would then shift operations away from SLS and away from its go-to EELV, Atlas V, for two Delta IV Heavy missions in 2020: the Mars 2020 surface rover (Curiosity’s beefed up cousin) and the ARRM (Asteroid Redirect Robotic Mission).

The Mars 2020 rover mission would launch in a window extending from July-Sept. 2020 and reach Mars in 2021.

This ARRM mission, slated to launch – pending funding approval – in December 2020, would pave the way for the future mid-2020s SLS crewed mission to the redirected asteroid that ARRM will bring back to a lunar orbit.

Shortly thereafter, in 2021, SLS and Orion would embark on their first crewed mission, the EM-2 Cis-lunar human flight on the SLS Block IB, 105t variant.

At this point, the SLS Block IB would undertake a non-stop once annual flight rate for a series of Cis-lunar missions through 2027.

In 2022, this annual flight would be the co-manifested EM-3 mission (with a crewed Orion mission coupled with the delivery of the Initial Cis-Lunar Habitation cargo element to Cis-lunar space).

Additionally, 2022 would also see NASA use another Delta IV Heavy rocket to launch the Mars Moon Explorers mission.

Then, 2023 and 2024 would see single manifested Cis-lunar flights for the EM-4 and EM-5 missions before the co-manifested EM-6 mission in 2025, which would perform the Asteroid Redirect Crewed Mission.

EMs-7 and -8, the last of the EM missions identified to date, would follow in 2026 and 2027.

At this point, SLS Block II would debut in 2028 with a massive ramp up of SLS launches to three that year.

The first mission of the new SLS Block II variant would fly in the first part of 2028 and launch the Pathfinder Entry Descent Landing (EDL) craft to Mars on a test flight for human flight EDL operations.

At this point, the number of SLS flights per year and per mission (Phobos or Mars) would vary depending upon which of two proposed Mars Transfer Vehicle options NASA chooses.

Regardless, the cumulative number of SLS flights needed at this point to perform the Phobos and first two human missions to Mars would remain the same, at 32, with only the flight sequence and payload of those flights undergoing option-specific changes.

Under the first option, a series of 9 SLS launches (between 2028 and 2033) would be needed for the Phobos mission – with one additional SLS flight of Orion needed in 2035 to return the Phobos crew to Earth after they return to Cis-lunar space.

Thus, the total number of SLS flights needed for the Phobos mission under option one stands at 10.

Another 11 SLS flights (between 2034 and 2039) for the first human Mars surface mission would then take place, followed by one SLS flight of Orion in 2042 to return the first Mars surface crew from Cis-lunar space – for a total of 12 SLS flights.

Moreover, 9 SLS flights (between 2038 and 2043) would then be needed for the second human Mars surface mission, with one additional SLS flight in 2046 needed to return the second Mars surface crew to Earth from Cis-lunar space – for a total of 10 SLS flights.

Under the second option, just 8 SLS flights would be needed for the Phobos 2033 mission, while a total of 14 SLS missions would then be needed for the first human Mars surface campaign.

The same number of SLS fights, 10, would be needed for the second Mars surface mission.

(Images: Via NASA and L2 – including SLS renders from L2 artist Nathan Koga)

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