Deimos Dust for Mars Orbit Insertion
A friend proposes a fast transfer to Mars; 10 to 20% more delta V at Earth results in a much faster trip there. However, the arrival velocity would be MUCH higher, and difficult to shed by aerobraking without high lift (and high centripedal gees) to remain within the appropriate density layer of the atmosphere of this small, low gravity planet. The v²/r - g acceleration arriving at Mars would be much higher for Mars than for Apollo.
The difficulty is worse for large heavy spacecraft; there is not enough atmosphere for a low speed parachute landing.
Mars Missions in the Age of Robots
Going to Mars with microbe-infested humans is also a very bad idea, possibly the worst scientific crime of the millenium. If a motivation for a Mars mission is a search for life, it is likely that the only life found will be the microbes shed by humans. A robot probe can be autoclaved; humans cannot. However, humans can go to prepared habitats on Phobos, and control robots from there. Getting to Phobos will be as difficult as landing with aerobraking.
Before humans go to Mars, we must rule out the possibility of ancient life anywhere that human contamination can reach. The Martian atmosphere is thin, but it is windy and connects the whole planet. So, we should explore the most of the surface with robots, ruling out surface fossil life to a very high confidence level in every possible kind of niche. Mars is frozen; it is reasonable to assume that (with proper precautions) material below the surface ice level can be kept absolutely free of contamination. However, the robotic exploration of the planet will require very many robots a very long time.
If we screw this up, we destroy our chances of learning the truth - forever.
Phobos Low Station
But what if there is a cheap way to get robots to Mars, and humans to Phobos, to operate those robots from a close enough distance to simulate "walking on Mars in a space suit" via telepresence, taking advantage of rapid lightspeed communication from Phobos, or Low Mars Orbit, or from a manned station on a tether hanging down from Phobos? The round trip speed of light delay from a station at 1000 km, through a chain of relay satellites, to a surface station on the opposite side of Mars is less than 10 milliseconds. We are laearning to operate robot submersibles in the ocean from much larger distances.
The "gravity" experienced on this hanging station would be "only" 2.2 m/s², only 60% of Mars surface gravity, but that also means the tether can be made without unobtanium. See AcousticClimber for a way to power climbers up and down that tether to the main base on Phobos.
We continuously monitor the distance to the LAGEOS laser geodesy satellites to micrometer precision, through a thick and turbulent atmosphere. These satellites are now the reference standard for all surface measurements on Earth. They are accurate enough to observe the slow drift of the continents via plate tectonics, and calibrate the GPS navigation system. They are inert balls of aluminum and brass covered with retroreflectors. It is conceivable that we could use them to calibrate GPS directly, and achieve nanometer precision with signal averaging.
We do vastly better with LIGO era laser technology, with 1e-22 precision. That has been compared to measuring the distance to Proxima Centauri to an accuracy of the thickness of a human hair. With distributed retroreflectors and an accurate computer simulation of the solar system, we can make hyperprecise calculations of positions and orbits. If we make this a priority, we can compute the position of spacecraft and electromagnetically launched objects to millimeters over gigameter distances. That means we can learn to hit a very small bullseye over solar system distances.
Harenodynamic Braking with "Deimos Dust"
In the early 1980s, Krafft Ehricke wrote about a "slide lander" for braking lunar landers to a stop on the Moon, without using propellant on board the vehicle. The vehicle would skid to a stop on a carefully prepared runway. That was in a low-accuracy era, but the spacecraft would need to be lined up to millimeter precision and milliradian trajectory angles to remain in contact with the runway all the way from orbital velocity to a stop.
An interesting idea, but we can do better. We can use low velocity mortars or short launchloop style accelerators to launch packets of carefully sorted lunar dust into the center of the path of a lander's heat shield, detals here. A vehicle travelling from Earth will arrive at 2520 m/s and require careful aiming; however, a 1500
Escape velocity from Deimos orbit to an interplanetary orbit is 1.35 km/s. Deimos is 1.47e15 kg of rock and sand. can be mechanically converted into arbitrarily small grains of dust, sorted by size electrostatically in high vacuum.