So, who's for Mars then?

[cjameshuff]

Not fuel; propellant. There's a difference.

Ship up some extra LOX and it could be both.

[ka9q]

You know, the ISS is already making oxygen from urine and exhaled moisture.

[Dalhousie]

People should read the original paper

http://inspirationmars.org/IEEE_Aerospace_TITO-CARRICO_Feasibility_Analysis_for_a_Manned_Mars_Free-Return_Mission_in_2018.pdf

[Inanimate Carbon Rod]

People should read the original paper

http://inspirationmars.org/IEEE_Aerospace_TITO-CARRICO_Feasibility_Analysis_for_a_Manned_Mars_Free-Return_Mission_in_2018.pdf

Why don't you summarise it for us? You appear to have all the answers.

[Dalhousie]

People should read the original paper

http://inspirationmars.org/IEEE_Aerospace_TITO-CARRICO_Feasibility_Analysis_for_a_Manned_Mars_Free-Return_Mission_in_2018.pdf

Why don't you summarise it for us? You appear to have all the answers.

No, only some.  Because I clicked and read.

Since you asked, here are some details:

Authors - Dennis Tito (Wilshire Associates Incorporated), Grant Anderson, Barry Finger, Gary Lantz, Taber MacCallum, Jane Poynter (Paragon Space Development Corporation), John Carrico, Jr. (Applied Defense Solutions, Inc.), Jonathan Clark, (Baylor College Of Medicine), Michel Loucks (Space Exploration Engineering Co.) Thomas Squire and S. Pete Worden (NASA Ames Research Center).

Title

"Feasibility Analysis for a Manned Mars Free-Return Mission in 2018"

Abstract

In 1998 Patel et al searched for Earth-Mars free-return trajectories that leave Earth, fly by Mars, and return to Earth without any deterministic maneuvers after Trans-Mars Injection. They found fast trajectory opportunities occurring two times every 15 years with a 1.4-year duration, significantly less than most Mars free return trajectories, which take up to 3.5 years. This paper investigates these fast trajectories. It also determines the launch and life support feasibility of flying such a mission using hardware expected to be available in time for an optimized fast trajectory opportunity in January, 2018.

[Dalhousie]

The mission, which uses an unusual low energy and fast free return trajectory that occurs on two successive windows every 15 years, will last 501.5 days.  Launch date will be January 15 2018, Mars arrival after 227 days on August 20 2018, Earth arrival after a further 274 days May 21 2019.  Landing could occur up to 10 days later, depending on which aerocapture profile is used for the 14.18 km/s entry.

The preferred crew is 2, one man one woman is implied (and stated specifically in the press conference).

The life support system is expected to mass 2,432 kg and have a volume of 6.6 m2, peak power requirements of 5,489 watts and average power of 2,208 watts.  Supplies will mass 3,131 kg and occupy a volume of 17.7 m3

State of the art technology of TRL 9 is preferred. Critical system spares will be carried and the system will be designed for ease of servicing and repair.

Air (sea level N2 & O2 mix and pressure) will be stored at high pressure and recyled through a molecular sieve, Sabatier reactor (to producde water), and electrolysis of water (to produce oyxygen), water will be processed through multi-filtration, ion exchange, distillation, and catalytic oxidation of waste to recycle at 75% efficiency.

Falcon Heavy and Dragon is used as indicative hardware, although, as the press conference showed, more volume than Dragon alone is needed and no decision has been made.

[Chew]

Think of the consequences of putting a bowel movement a day by two people overboard for 500 days (that's a thousand movements at least) on a mission without any major orbital changes and you can work out why jettisoning it is not going to be a good idea.

Assuming two 1 kg turds (and those are big turds) per day for 500 days ejected at 1 m/s from a 10 ton spacecraft will accelerate the craft by 0.1 m/s. The fuel required to compensate for that acceleration is about .33 kg. It's not that big a deal. Sure, use it for shielding but don't say there is no other place to put it.

Not even close to the reason.

So what is the reason?

[Dalhousie]

Inspiration Mars's reason is that it is too useful to dump.

Additional issues I can come up with regarding dumping include:

Planetary protection - this is a close flyby 100 km and if gthe spacecfraft is surrounded by an expanding cloud of human waste there is a chance that some will end up on Mars.  Small maybe, not not worth it, especially when it is not neccessary.
Obscuration of the view - constellation Urion aused some annoyance to astronauts takingstar sights during Apollo, hundreds of waste bags could do the same, not to mention imaging opptunities during the flyby.

Air loss - a small amount will be lost each dump, they may wish to avoid this.

But the main reason is what they have stated - it is too useful onboard.  The amount is not that large anyway- 109 kg for the total mission (dry mass).