I. Cargo Capacity Increases
We have sufficient lifting capability with current rockets to put cargo and humans on Mars. The SpaceX adapted Mars Semi-Direct mission mode prescribes multiple vehicles lifted by Falcon Heavies, which can each put 53 tons of cargo into LEO and 14 tons into Mars orbit, and 11 tons on the surface of Mars.
Some proposed logistics: http://i.imgur.com/jEWaQsZ.png
The United States has launched seven successful (out of seven attempted) vehicles into Mars’ orbit or surface since 2001.
Mars Exploration Rover — Spirit
Mars Exploration Rover — Opportunity
Mars Reconnaissance Orbiter
Phoenix Mars Lander
Mars Science Laboratory
Mars Atmosphere and Volatile Evolution
III. Mean time between failures
Rad-hardened, fault-tolerant, redundant systems are well understood. Opportunity was flown to Mars, landed on it, and has been operating on its surface for 11 years — and our tech has improved since then.
Using the Mars Semi-Direct mission mode or some variant means crew on the ground have backups of all their vehicles and habitats, and that those vehicles are replaced every couple of years — far lower than their expected lifetimes.
IV. Jet fuel
SpaceX plans to use their new Raptor rocket engine in the Mars Colonial Transporter, which will burn liquid methane and liquid oxygen.
This design has numerous improvements over existing kerosene and LOX rockets, which have themselves proven sufficient to move vehicles to Mars, many times.
If this was a showstopper, how did we do it so many times in the past?
V. Cosmic Radiation
Many (about a dozen) astronauts and cosmonauts have been exposed to similar or greater amounts of cumulative cosmic radiation doses during their stays on the ISS and Mir as they would during an unshielded round-trip to and from Mars. None of them have experienced any radiological health effects. Fatal cancer risk is low.
Anybody demanding five nines of safety can quit now and just stay home.
For detailed analysis of surface radiation, see:
Solar has been proven successful by many Mars missions. Power is generated both at night and during prolonged dust storms.
There are other options; radioisotope thermoelectric generators have been used regularly for over 50 years, including in the Curiosity rover.
VII. Living module
Astronauts travel out in a SpaceX Dragon, modified to include an inflatable cabin to be deployed once on-surface.
VIII. Microbial realities
NASA has 15 years to figure this one out.
Monitoring Microbial Ecosystems on the International Space Stationwww.nasa.gov
Despite a 3–7 increase in space-grown Salmonella virulence, current and past astronauts have not experienced ill effects. Quite likely the result of this research will be nothing more than a simple anti-microbial spray.
Will very likely rely on a powered landing for the human-carrying vehicle.
Unmanned vehicles can be dropped pretty hard.
Entry, descent, and landing of large payloads on Mars is challenging but not insurmountable.
See: III. Mean time between failures
XI. Eye Sight
Most mission plans counteract microgravity effects with some form of rotation-induced artificial gravity — most commonly by tethering the occupied habitat unit to the spent upper stage of the rocket booster and rotating them around a common axis.
NASA’s report indicates that the effects “do not appear to be severe enough to cause blindness near term.”
XII. Muscle loss
Data from ISS shows that with 2.5 hours per day of exercise, strength loss appears to stop at around a 20% decrease.
There are a variety of health effects on humans caused by reduced gravity, of which muscle loss and visual impairment are only two.