New Mars Forums

Abstract : Propulsion systems composed of a Shuttle External Tank, appropriately modified for the purpose, with a rocket engine that is either an SSME or a NERVA could inject a gross personnel payload of 100,000 lb on a trans-Mars trajectory from Space Station Freedom with aerobraking at Mars with transit times of less that 70 days. Such transit times reflect a significant reduction from the 200- plus days generally considered. The 100,000-lb payload would include the mass of a hypothetical aerobrake for aerocapture at Mars. The entry velocities at Mars compatible with such transit times are greater that 21 km/sec, to be compared with previously stated constraints of 8.5 to 9.5 km/sec for nominal Mars entry velocity. Limits of current aerobrake technology are not well enough defined to determine the feasibility of an aerobrake to handle Mars-entry velocities for short-transit-time trajectories. Return from Mars to Earth on a mirror image of 70-days outbound trajectory (consistent with a stay time of about 12 days) would require a Mars-departure velocity increment more than twice as great as that at Earth departure and would require a correspondingly more capable propulsion system. The return propulsion system would preferably be predeployed at Mars by one or more separate minimum-energy, 0.5-to-1.1-Mlb-gross-payload cargo flights with the same outbound propulsion systems as the personnel flight, before commitment of the personnel flight. Aerobraking entry velocity at Earth after such a transit time would be about 16 km/sec, to be compared with constraints set at 12.5 to 16 km/sec.

...
I like your idea of using a Moon flyby to get an extra 500 m/s delta-V for a Mars mission. On the "Mars Semi-Direct with Falcon" thread you mentioned that a shorter outbound transit time is made possible with a 4.3 km/s delta-V, rather than the Hohmann trajectory delta-V of 3.8 km/s. Then you could use the lunar flyby to get the extra 500 m/s for the shorter transit time.
I wonder if it may be possible to also use the Oberth effect with respect to the Moon at the same time as the lunar gravitational slingshot since they are distinct effects. With a lunar escape velocity of 2.4 km/s, you could get an extra delta-V close to this with the Oberth effect.

We had a lot more on this before the Great Crash...

According to Atomic Rockets, Solar Moth would get 900s, 4000N @ 100kg. If we use Ammonia, we could perhaps get higher thrust for lower Isp, and using an oxygen after burner, we could increase the thrust further, though again at the expense of Isp.

One of it's main attractions for me is the possibility of using a storable propellent such as Ammonia while still achieving high Isp, as well as obiviating the need for a heat shield. I think we need to take a good look at the varius components of rockets and see how we can minimise their masses or even do away with them entirely.

The main driver of Platinum high price is automotive Catalytic Converter usage which is something like 30% of consumption if I recall correctly.

A completely separate team has now announced plans to do mining from
the Moon:

Renowned scientists join tech visionaries at Moon Express to mine the
Moon for planetary resources.
“MOUNTAIN VIEW, Calif., April 24, 2012 /PRNewswire/ -- Moon Express, a
Google Lunar X PRIZE contender, announced today that some of the
world's leading planetary scientists have joined its Science Advisory
Board (SAB) to assist the company in its plans to explore and
ultimately mine the Moon for precious planetary resources.”
http://www.prnewswire.com/news-releases … 32035.html

  Bob Clark

In regards to the reason for this endeavor, several studies have shown many of the important metals for high technology such as platinum at present global growth rates, especially in the emerging economies such as China, will be depleted within decades:

Earth's natural wealth: an audit.
23 May 2007
NewScientist.com news service
David Cohen
http://www.science.org.au/nova/newscien … ns_005.htm

If these reports are true, and there is some uncertainty in the estimates, then such asteroid mining missions, might turn out to be not amusing topics of discussion, but actual necessities.

Abstract
The relative proportions of metal residing in ore in the lithosphere, in use in products providing services, and in waste deposits measure our progress from exclusive use of virgin ore toward full dependence on sustained use of recycled metal. In the U.S. at present, the copper contents of these three repositories are roughly equivalent, but metal in service continues to increase. Providing today's developed-country level of services for copper worldwide (as well as for zinc and, perhaps, platinum) would appear to require conversion of essentially all of the ore in the lithosphere to stock-in-use plus near-complete recycling of the metals from that point forward.

Abstract
The global demand for platinum has consistently outgrown supply in the past decade. This trend likely will continue and the imbalance may possibly escalate into a crisis. Platinum plays pivotal roles in both conventional automobile emissions control and the envisioned hydrogen economy. A platinum crisis would have profound implications on energy and environment. On the one hand, inadequate platinum supply will prevent widespread commercialization of hydrogen fuel-cell vehicles. On the other hand, expensive platinum may enhance the competitiveness of hybrid, plug-in hybrid, and battery-powered electric cars. Policymakers should weigh the potential impacts of a platinum crisis in energy policy.

...
Again because the delta-V requirements to a NEO are less than those to the Moon, this lander/rover could also serve as a prospector for asteroid missions. There was a recent article discussing the idea that a loophole in the Outer Space Treaty might allow private land claims on outer space bodies:

Loophole Could Allow Private Land Claims on Other Worlds.
By Adam Mann | April 5, 2012 | 6:30 am | Categories: Space
http://www.wired.com/wiredscience/2012/ … -property/

Then the intriguing question arises: could landing of such a low cost rover on a NEO allow the Astrobotic backers to claim full mineral exploitation rights on potentially a $20 trillion asteroid?

Article VI
States Parties to the Treaty shall bear international responsibility for national activities in outer space, including the moon and other celestial bodies, whether such activities are carried on by governmental agencies or by non-governmental entities, and for assuring that national activities are carried out in conformity with the provisions set forth in the present Treaty. The activities of non-governmental entities in outer space, including the moon and other celestial bodies, shall require authorization and continuing supervision by the appropriate State Party to the Treaty. When activities are carried on in outer space, including the moon and other celestial bodies, by an international organization, responsibility for compliance with this Treaty shall be borne both by the international organization and by the States Parties to the Treaty participating in such organization.

Mating of unrelated payloads to carrier does take time and is usually part of a 6 year mission design to reality that most satelites and even Nasa uses for its landers, orbiters ect....with selected launcher. I think this is too long for a developement time but its also the item of payload that takes all the work....launcher build time is less than 2 years of it.
The robots discription is interesting...
the robot will operate for 10 to 12 days of constant sunlight, then hibernate during the equal period of polar nighttime.
Astrobotic Technology, one of 26 teams competing for a $30 million Google Lunar X Prize, has altered its October 2015 mission to the moon in dramatic fashion.
http://lunarnetworks.blogspot.com/2012/ … -high.html
http://lunarnetworks.blogspot.com/2012/ … s-for.html
http://www.lunarrover.org/
http://www.googlelunarxprize.org/teams/astrobotic

...
The three decks of the capsule-shaped vehicle together have a volume of 52 cubic meters; the Space Shuttle provided 68, if I recall, so it's similar in size to the shuttle. The mass includes 1.5 tonnes for an inflatable and furniture (Zubrin used 200 kg for a two-person inflatable). I am assuming a crew of up to 7. If the inflatable fails en route they'd have to retreat into the Gryphon and the space would be very tight, but presumably people would survive. The 10 metric tonnes of cargo would be the 4 metric tonnes of consumables needed on the trip out plus 6 metric tonnes of various things the crew of 6 needs on the surface (some essential equipment, some consumables). The rest of the consumables and equipment arrives by Hohmann trajectory 2 months after the crew arrives. Ideally, the hab can be retracted, deorbited to the Martian surface, and used there as well.
The delta-v of 4.4 km/sec is carefully chosen; that's what you need to go from low Earth orbit to Mars in 6 months (4.3 plus 0.1 for mid course corrections). You need 4.1 km/sec to go from the Martian surface to low Mars orbit; very similar. The idea is to refuel the vehicle in low Earth orbit, launch to Mars, aerobrake, refuel in low Mars orbit sufficiently to land, refuel on the surface, return to low Mars orbit, refuel there sufficient for TEI, and head for Earth. The fuel in Mars orbit could be made on Phobos, Deimos, or the Martian surface and delivered. A round trip would require 55 tonnes out, maybe 5-10 tonnes to land, 55 tonnes to return to Mars orbit, and about 15-20 tonnes for TEI.

"Bamboos are some of the fastest growing plants in the world,[2] as some species have been recorded as growing up to 100 cm (39 in) within a 24 hour period due to a unique rhizome-dependent system."
100cms in 24 hour sounds the sort of plant we want and need on Mars.

The issue of the "depth" of the gravity well needs to be remembered, though. Basically, the way the "gravity slingshot" works is that the object you are passing changes the direction of your flight. Relative to that object, though, the momentum does not change and you leave the object with the same relative speed you approached it. If you fly by Phobos, it doesn't have the gravity to bend your path significantly. Maybe each encounter can give you a couple meters per second and after a few years your spacecraft is in a highly elliptical orbit. Maybe Phobos can fling you to a few meters per second more than Martian escape velocity, eventually. But that won't get you to Earth, and it may take a looong time. I doubt Luna can bend one's trajectory much, either; otherwise, they would have used it already.
Can you use the gravity slingshot and the Oberth effect? I'm sure you can. The Earth just knows your direction and speed and pulls on you based on your distance.