NASA’s existing architecture for Mars Sample Return is facing cost and schedule pressures, leading for some to argue for a radical rethink of the program. (credit: NASA)

An alternative Mars Sample Return program

by Dale Skran
Monday, August 19, 2024

There have been many reports in the news lately about the growth of the Mars Sample Return (MSR) budget in publications like Science and SpaceNews, with widespread fear that either the ballooning MSR budget eviscerates the other NASA planetary programs, or that MSR will eventually be cancelled and the money transferred to Artemis. This situation has resulted in a number of re-dos of the MSR architecture, which appear to have done little to lower costs or create improved results. More recently, NASA has initiated a series of layoffs at JPL that mainly impact MSR, apparently in anticipation of significant budget cuts, leading to further alarm among supporters of space exploration. NASA recently solicited industry input on alternative approaches to MSR under the title “Rapid Mission Design Studies for Mars Sample Return,” selecting several companies in June for short mission concept studies.

As currently envisioned, MSR does little to advance Mars exploration in the long run, and by sucking up a lot of budget and energy may arguably wreak havoc on the rest of the NASA robotic exploration program. An obvious alternative is to re-invent MSR as the first step toward landing humans on Mars rather than as a one-shot effort consisting of technology that is unlikely to benefit a human mission to the surface of Mars.

There is an elephant in the room: the SpaceX Mars architecture built around Starship/Super Heavy. Despite having partially bought into this approach in the Artemis program for usage as a Moon lander, NASA remains deep in “trade study hell”[1] when it comes to going to Mars. A significant tug-of-war appears to exist between those who insist a nuclear rocket is required for going to Mars with humans, and others, which include SpaceX, who favor the use of in-space refueling of chemical rockets. A more recent NASA trade study[2] concludes that “…the high ∆V required for fast Mars missions with short stay times drives the need for nuclear propulsion technology… past studies have shown that non-nuclear options require extremely aggressive technologies and concepts of operations to close a fast Mars mission. An apples-to-apples all-chemical ConOps is not likely to be viable.”

This study recommends chemically boosted nuclear-electric as the preferred solution over nuclear thermal propulsion. They likely are correct, but by focusing on short stay times on Mars with fast mission profiles, they exclude SpaceX’s Mars architecture from serious consideration, as well as all technologies such as in-situ resource utilization (ISRU) that lower costs over time and support a sustainable human presence on Mars. NASA has traditionally created expendable, mission-specific, self-limited, bespoke equipment for human exploration. Perhaps it is time for a new approach.

Given that NASA is already committed to making Starship/Super Heavy work as a lunar landing system, the logical next step would be to build on that experience and re-use the basic structure to land on Mars. What better way to test out that architecture than by using it for Mars Sample Return?

So, let us put on our “visioneering” hats and look at how MSR might look like if built around Starship. We would need more tanker flights than for a Moon trip, and since a fully refueled Starship has been designed to land on Mars, this seems like a good starting point. The next question is how we get the Starship off the surface of Mars and back to the Earth. Using ISRU to create fuel on Mars is probably a bridge too far for the near term, so fuel could be pre-positioned on Mars to power the return to Earth. Alternatively, refueling could be conducted in Mars orbit, both prior to the landing and after the landing to prepare for Earth departure. Either approach requires a significant number of fuel tankers heading to Mars, as well as highly reliable and effective cryocoolers and transfer/pumping equipment. The final required component of the system is a means to collect the samples and put them in the return vehicle.

Here is a chance for NASA to shine: multiple helicopters could be used to collect samples and return them to the Starship via a large door. This approach avoids the need for ramps, elevators, or hoists. It also creates flexibility, as the helicopters might travel a considerable distance to pick up samples. Also, there should be several helicopters for redundancy.

In this scenario, the fuel tankers are the test flights. They will continue to be sent until there is enough fuel on or around Mars for the return journey. Some of these landings will fail, but eventually success will be achieved. The resulting Starship will be capable of reliably landing on Mars and storing fuel for many years; both are key technologies needed to send humans on the Red Planet and return them to Earth. Now comes the moment of truth: the return Starship with the samples. Let’s say that the first one crashes. No harm done—it will be attempted again, and again, until it succeeds. The samples can be returned in tranches to ensure that at least some of them make it all the way back to the Earth.

The return to Earth may be further simplified by skipping a terrestrial landing and substituting docking with a space station in Earth orbit or the Gateway in a halo orbit around the Moon. Perhaps the safest way to initially quarantine samples would be on a space station, with a later return to Earth in a highly reliable cargo vehicle.

This entire program will almost certainly cost more than the $8–11 billion likely to be spent on the current MSR plan. However, it will also retire much of the risk involved in sending humans to Mars. The remaining components required to send crews to Mars include ISRU on Mars to locally produce fuel for the return trip and the environmental control and life support system (ECLSS) to keep the astronauts alive on a long voyage. With the pre-positioning of fuel on Mars or Mars orbit and refueling already perfected, the ISRU production of fuel might be skipped on the first crewed trip. These are not small things, but they are incremental to a Starship-based MSR plan. Also, the Mars trip ECLSS will be based on decades of ISS work, the Gateway ECLSS system, and the ECLSS built to allow Starship to land crews on the Moon. Additionally, there is the possibility that SpaceX will create a “space station” version of Starship with long-term ECLSS capability as a free-standing commercial entity.

What is on the table here is the potential for lowering the overall cost of sending humans to Mars while reducing risk substantially via extensive testing. The main challenge this plan will have to surmount lies in accepting that a significant number of Starships are going to be landing on Mars, with some of them crashing. There has been a good bit of discussion of what might be involved in “sterilizing” a Starship to meet the current super-stringent planetary protection rules. Among the many issues is that hundreds of tons of methane fuel would need to be “sterile”, something which strains credulity. There is going to have to be a major re-think on planetary protection for any humans-to-Mars program, but using Starship to support MSR would pull that debate forward in time.

Although in theory there is some risk of contamination in landing humans (or Starships) on Mars, it is also possible that we will never find life on Mars with the current program of a robot every few years. What may be needed to find life on Mars is a massive, intensive program of exploration that involves large amounts of drilling and extensive robotic exploration of hard to access locations. Such a program targeting dozens of locations all over Mars requires hundreds of tons of equipment, regular resupply, and may be best managed from a crewed base on Mars.

So, let’s deal a new deck of cards, abandon the current MSR architecture, and focus MSR on using Starship. The ability of Starship to land on a large planet has already been more extensively demonstrated (that is, a Starship has landed on the Earth) than any of the proposed MSR hardware, which exists only in PowerPoint slides. And the current NASA Artemis plan of record assumes rapid progress in Starship development, including multiple Moon landings.

Dale Skran is a serial entrepreneur and past ITU-T Rapporteur, as well as a Bell Labs alum. He currently serves as the Senior Vice President and Chief Operating Officer of the National Space Society. This article is his view, and not an official position of the NSS.

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