Apollo missions 11-17 succeeded because of Apollo missions 4-10 and all the other missions that preceded them. The research, hardware tests, flights and missions that preceded the human landings tested each element of the target mission, progressively improving confidence in the architecture, hardware, systems, processes and astronauts.
Precursor missions are not often described in conjunction with HMM architectures, perhaps because of the exorbitant cost of sending packages to Mars, or perhaps because the human mission itself is complex enough to describe. Perhaps it’s because precursor missions are considered less of a challenge or already addressed by robotic exploration.
However, once an architecture has been selected, it will be necessary to test as much of it as possible before attempting a human landing, just as with Apollo.
If the Red Dragon technology can reliably deliver 2-tonne payloads to Mars surface for only a few hundred million dollars per launch, a program of precursor missions that prove and develop the technology, in addition to testing other elements of the human mission, is affordable and can be included in the overall program.
A schedule of precursor Mars missions will enable improvement of the architecture. Many aspects of Blue Dragon can be tested on Earth, in Earth orbit, or on the Moon, but some are only truly testable at Mars, especially those related to EDL and ISRU. Examples include the following, some of which can be bundled together into the same mission:
- Test of the MAV, including EDL, ISPP, launch and ascent to orbit (everything up to, but excluding, MOR).
- Test of an ISAP system to produce breathable air from Martian atmosphere.
- Test of ISWP systems to extract water from the Martian atmosphere and ground.
- Test of solar power production on Mars using PV panels, material and coatings.
These are combined into the following proposed missions:
Green Dragon: a robotic lander that tests entry, descent and precision landing of a Red Dragon capsule, and all ISRU systems required by the SHAB, i.e. in situ production of electricity, air and water. Water and gases are obtained from the atmosphere and processed to produce breathable air and potable water. Power production using PV panels, blankets and/or coatings, and potentially also ASRGs, is also tested. If mass, volume and budget constraints permit, the mission may additionally test production of CH4 and/or CO, and the use of these in fuel cells to produce electricity, which in turn can provide power to the lander.
Gold Dragon: a MAV test. A MAV prototype is landed on Mars and the ISPP unit is activated, producing LOX/LCH4 bipropellant. Once full, the MAV is launched from the surface of Mars, and ascends to an orbit matching where Adeona will be, as if in preparation for MOR. This mission will test EDL of the MAV, PV blankets and coatings, ASRGs, the AWESOM robot, ISPP, and autonomous launch and ascent of the MAV.
These missions can benefit from the research already conducted for the MARCO POLO, Ice Dragon, Mars 2020 rover, and other related missions.
In a perfect Universe, a complete run-through of the mission with no crew involved would be a valuable test. After a successful predeployment phase, Adeona could be constructed and robotically flown out to Mars where it would wait on orbit for 1.5 years, then the MAV would be launched, the ascent capsule docked with the MTV then undocked, and the MTV robotically flown back to Earth and parked on Earth orbit. All of this could actually be done without a crew. However, this would be a very lengthy and expensive test, and unlikely to be practical or truly necessary. A combination of simpler precursor missions, simulations, and Earth-based missions will suffice, as they did with Apollo.
12.1. Green Dragon
Green Dragon is a precursor mission to the HMMs, which will land a Dragon capsule on Mars containing integrated ISRU hardware capable of manufacturing breathable air and potable water from local Martian resources. The mission is designed to advance capabilities and build confidence in two main areas: EDL and ISRU.
12.1.1. Entry, Descent and Landing
One of the main reasons for Green Dragon is to gain practice landing Red Dragon capsules on Mars, refine the technology, and build confidence that this can be done repeatably and safely. If Mars One is successfully implemented before the IMRS program is commenced, then EDL via capsule may already have been proven. In any case, the more this is practiced, the better. Ideally, at least a few capsules will have been successfully landed on Mars before using one for landing a crew:
- 1 for Green Dragon
- 2 or more supply capsules
- Any capsules sent by Mars One
The more capsules landed on Mars before sending humans, the more confidence mission planners will have in the technology before landing a crew using the same technology. It’s necessary to know exactly how capsules behave during EDL to Mars, how they interact with the Martian atmosphere and surface, how to land on a dime, and where the strengths and weaknesses are in this approach. Although much can be simulated, nothing will deliver as much insight as actually landing a capsule on Mars.
It’s essential to test and, where possible, improve the accuracy of landing. SpaceX claim that Dragon capsules will be capable of pinpoint landings on Mars; other navigation algorithms that could be tested in this mission include LION and G-FOLD.
12.1.2. Integrated ISRU
The other main purpose of the Green Dragon program is to increase the TRL of ISRU technology in preparation for sending humans to Mars. The intention is to test ISRU systems for producing breathable air (O2 and buffer gas), potable water, and potentially also CO for use in a fuel cell. A secondary goal is to create a backup cache of critical resources near the IMRS that may be accessed in case of emergency. Green Dragon effectively simulates ISRU systems for the SHAB.
Green Dragon includes three integrated ISRU experiments:
- ISEP (In Situ Electricity Production) - Electrical power is produced from solar energy using one or more rolls of PV material.
- ISAP - O2 and CO are obtained by electrolysis of atmospheric CO2 using SOECs. Buffer gas comprised primarily of N2 and Ar is produced by drying and detoxifying the gas mix that remains after CO2 is removed from Martian air. The CO is retained for use in a fuel cell, producing additional electricity to power the spacecraft.
- ISWP - Water is extracted from the atmosphere via adsorption in zeolite 3A.
12.2. Gold Dragon
Gold Dragon is simply an automated MAV test.
Launching from the surface of Mars is one of the greatest challenges in HMMs, which is why it was omitted from Mars One, and why some people favour one-way human missions.
However, considering SpaceX’s RLS (Reusable Launch System) technology, Masten Space Systems’ Xombie rocket, Blue Origin’s New Shepard VTOL rocket, and other developments currently underway in space, energy, materials and manufacturing, development of a MAV in the required time frame definitely seems achievable.
Operation of the MAV is more-or-less impossible to properly test on Earth, and it would be risky (perhaps unacceptably so) to attempt to launch humans from the surface of Mars without having tested this launch system at least once.
The Gold Dragon MAV will be flown to Mars, landed somewhere close to the planned IMRS location, filled with propellant over a period of months, and launched to Mars orbit. As there will be no MTV on Mars orbit at the time, the only part of the MAV lifecycle that will not be tested by this mission will be the docking of the Mars Ascent Capsule (i.e. Kepler) with Adeona. After being placed in the 250 km x 1 sol orbit, it may be left there for later recovery, or de-orbited to fall back to Mars.
The reason why the Gold Dragon MAV needs to be landed close to the IMRS is to test water extraction from the same latitude and type of terrain that the MAVs used in the human missions will encounter.
The intention is to send a Gold Dragon mission at least once, and perhaps again if results indicate that the vehicle needs to be further improved before it can be declared human-rated. While this would be expensive, the ISPP system and MAV ascent are firmly in the critical path of the mission and it’s essential they work as planned.