Monday, November 17, 2008

Crew Health Basic Numbers

These basic numbers are conservative estimates for a no-GCR/Solar storm shelter style space mission, and assumes that a really good closed physical life support system (CPLSS), as opposed to more advanced closed ecological life support system (CELSS). Note that I'm not arguing against CELSS, merely assuming that it will not be available for space cruise on early missions.

Mass per crew member:
85kg the naked crew member
15kg personal margin
30kg arbitrarily budgeted for shared medical equipment of best return on investment for mass
30kg transition suit (worn during dockings, ascents, entries, etc.)
30kg seat
20kg two spare transition suits for every three crew members
20kg kit to convert transition suit to EVA suit
15kg conversion kit spares (equivalent three for every four crew members, but will probably concentrate on high wear items, including gloves and CO2 adsorbent cartridges.)
5kg fire extinquisher
5kg personal computer
5kg personal medical kit (not to be confused with medical equipment above.)
10kg Emergency Open Life Support kit (i.e.: SFOG or superoxide cartridges to allow time for emergency life support shutdown during "shirtsleeve" periods. Does not protect against depressurization
50kg Margin for stuff I might not have though of, or underestimates in the above.
320kg total per astronaut

250kg pressure shell in the transition vehicle for each crew member (based on an average from several pressurized aluminum aircraft cabins)
90kg inflatable pressure shell for each crew member (a calculation based on the ASME B&PV Sec VIII, Div 1 spherical head formula for 15psig, 20ksi AWS, density 4.0kg/L material at three different diameters showed 4.5kg/m3 would be used...20m3/pax is a good cabin volume...hopefully you understand this if you're a pressure vessel engineer.)

660kg Total per crew member, fixed mass in space
2000kg Total per 3pax section (rounded up from 1980kg) Of this, 1250kg would be in the Cruise Hab during space cruises, and the other 750kg would be in the transition vehicle.

Unrecovered consumables per person day
2.0kg water (assumes 20kg of water used per day recycled at 90% efficiency)
1.0kg oxygen (assumes 2.0kg of oxygen used per day recycled at 50% efficiency...100% electrolysed water, 50% electrolysed or RWGS'd CO2, allows for leakage.)
2.0kg food
1.0kg solid waste (stuff like toilet paper, garbage bags, duct tape, commode chemicals, etc.)
1.0kg other/margin (stuff like bandaids, shampoo, laundry soap, toothpaste, socks, etc.)
7.0kg total per pax-day

500 pax-days per kit (after I figured out how much would fit in 6000kg, which just happens to be Stampede Lander's capacity.)

1000kg water (5% dunnage margin)
500kg oxygen (10% dunnage margin)
1000kg food (20% dunnage margin)
500kg solid waste (0% dunnage margin...i.e.: this is the dunnage for solid waste)
500kg other/margin (20% dunnage margin)
3500kg total

Values with dunnage margins (dunnage = tanks, lockers, packaging, etc.)
1050kg water
560kg oxygen
1250kg food
500kg solid waste
630kg other/margin (edit point)
3990kg total

This is the "supply trailer" package for non-ISRU life support, allowing for a 2000kg mobility system to accompany it. A first mission with six people requires N+1 supply trailer redundancy and 500 days of supplies. This results in seven supply trailers (yikes).

Space Supply Package: This one is more important because on the surface, we should be able to use ISRU water, although we'll really need seven supply trailers if we can't prove that we can make Mars water potable with the equipment the crew has on hand before they fly the first mission. Seed hydrogen for surface use has not yet been ruled out, but I'm not going to address it in this post.

A crew will need 15oo pax days for each leg of the journey, allowing 250 day cruises each way. For shorter cruises, it's easy to substitute equipment, or even increase the performance transfer for an even faster cruise (up to the limits of the lander's ability to arrive at Mars going fast.) The Space Supply Package is included with the Cruise Hab (has 1250kg on it already), to a limit of 14000kg. We've established 8kg/pax-day including dunnage, so the remaining 12750kg of Cruise Hab, 1594 crew days. This means that the 14000kg lift ticket is probably very close to the minimum necessary for a human to Mars mission. (This 14000kg is launched to a 24 hour assembly orbit, or to a libration point, which is why a 45 tonne class booster, in LEO terms, is required.)

Surface package (with 100% ISRU water and oxygen):
1.0kg solid waste/pax-day
2.0kg food/pax-day
1.0kg other-margin/pax-day

Supplies for 800 pax-days on surface:
800kg solid waste
1600kg food
800kg other-margin
3200kg total

With dunnage:
800kg solid waste
2000kg food
1000kg other-margin
3800kg total

Thus, with a requirement of 3000 pax days for a six person crew, four supply trailers are needed, and a fifth for redundancy at landing.

That's it for this post. More later

Wednesday, November 5, 2008

Stampede Lander

Most of this was lifted from post #119 on the marsdrivemission Yahoo group. The actual concept work was done on or about 23 June 2007.

The Stampede Lander details: Entry Mass: 12000kg
Aeroshell Diameter: 6.5m
Aeroshell Drag Coefficient: 1.40
Aeroshell Lift Coefficient: 0.42
Aeroshell L/D: 0.30
(this is all achievable using the Apollo Command Module as a basis)
Ballistic Coefficient: 303 kg/m2

With roll control, inertial guidance and a navigational fix less thanan hour prior to entry interface, it should be possible to achieve anaccuracy to a 20km diameter circle (3-sigma limits), or a circular error probable (CEP) of 5km.

Parachute Mass: 530kg
Parachute Diameter: 30m Disk-Gap-Band
Parachute Drag Coefficient: 0.67
Parachute Opening Mach: 3.0
Parachute Opening Speed: 705m/s
Parachute Opening Dynamic Pressure: 2000Pa
(This parachute is therefore quite heavy for its size.)

Heatshield Mass: 1800kg (estimated at 15% of total, probably overkill)
The propulsion system is a 3000m/s (305.8sec) specific impulse hypergolic bipropellant system giving the lander a terminal crossrange of 4000m just in case the cameras show that the poor thing is headed towards a patch of unfriendly terrain that was accepted as a risk within the entry targeting zone. If the targeting zone is a point in flat terrain, Stampede should be able to put you down right on the spot about a third of the time, and is guaranteed (i.e.: 99.7% if everything works fine) to get you within 6000m, as long as there's a beacon on the target.

After the parachute opens, your beta will be 25.3kg/m2, giving you a terminal speed of 132.2m/s in atmosphere with a density of 0.011kg/m2 (Earth's atmospheric density at the equivalent Martian surface pressure; the actual air density is higher at the surface, but will be in this ballpark at parachute altitudes.) Your heatshield has a beta of 45.8kg/m2, which means it will come off just like it does in robotic missions (most larger landers can't do this.) After jettisoning the heatshield, your beta will be 21.5kg/m2 allowing you to slow to 121.9m/s before having to light the rockets. By this point you'll be hanging under the backshell, which contains the rocket motors. Assuming the worst case crossrange+margin maneuver will be performed, the backshell will begin firing at a tilt angle of 29.4deg from the vertical, inducing an accelleration of 12m/s2 (which will probably feel like about 3g after the interplanetary coast.) After 22.1sec, you'll be travelling horizontally at 132.7m/s. The parachute is jettisoned with a rocket when its riser slackens or exceeds a certain tilt angle. You will be 1500m from the original impact point. The craft then tilts the other way and fires its motors, inducing 4.2m/s2 of accelleration to maintain altitude and slow down. You'll come to a stop after 60.3 seconds, 5500m from the initial impact point...then run out of propellant and crash because this scenario used up the touchdown margin. The system's total delta-v is 536.5m/s, the system is assumed to have a maximum induced accelleration capability of 12m/s2 and throttles back to maintain that maximum. The tank mass is given 6% of thepropellant mass, and the motor mass is calculated on a basis of 350N/kg, producing a total touchdown propulsion system mass of 2011kg. There are 7659kg remaining in the vehicle, 1659kg (13.8% of the entrymass) is left to the rest of the landing system (backshell, hovercrane lowering system), and 6000kg is the payload.

Update 18 July 2008: I switched from a hover crane touchdown system (which loses the backshell), to a reusable overhead platform. In this type of lander, the legs are mounted on the backshell and extend astride the payload (typically a rover.) The payload has its own suspension, and may be lowered on flexible struts or a really short set of tethers. Once down, the rover can roll out from underneath the platform, or the platform can relight its motors and land somewhere else to clear the payload...assuming it has enough propellant to do so.

Saturday, November 1, 2008

Yahoo Group

Discussion of the After Columbia Mars Direction is invited at

Introduction to After Columbia Mars Direction

After Columbia Mars Direction is a third generation architecture for getting humans to Mars and back. It is applicable to exploration and colonization missions, but the version I (and if applicable, my group of volunteers ;) will work on here will concentrate solidly on colonization. The assumption of the colonization mission is that it initially operates with the same elements as an exploration mission, but the return boosters are for returning the crew if the colonization effort proves premature and they are unable to stay on Mars.

Who am I? Terry Wilson...don't google for that, google for "aftercolumbia" instead, you'll never find me by googling for "Terry Wilson"...I've tried. You might be wondering about my history and credentials as it regards mission design. They are deeply intwined with the history of After Columbia itself, but I will start at the beginning:

In April 2001, in dated notes, I begin working on mission concepts for hard science fiction concepts...just a fancy hobby, basically. The difference is that I uncovered the Tsiolkovsky rocket formula, which shows the relationship between the portion of fuel a rocket vehicle carries, and how fast it can go as a multiple of how fast its exhaust goes. I found it in one of Robert Zubrin's books, most likely The Case For Mars. This was 22 months before the STS-107 accident.

July 2002. There was a huge upheaval in my life, leaving me an emotional wreck, but I need not share the details here. I began a new career in construction partly as a result of this. It lasted until 31 January 2003. It took me about that long to recover from this upheaval in my life. I had poked around some mission concepts, primarily a Saenger II/SpaceBus type two stage runway operated reusable booster called Bluestar.

1 February 2003. I had planned to watch the landing of STS-107 live...I remember exactly where, at an all-night cybercafe with plenty of video-friendly bandwidth. I thought she was landing on 2 February 2003 and missed it. About eleven hours after (watching, among other things on movie channels that never interrupt their broadcasts for significant news, Black Hawk Down.) I started to think of Columbia and started surfing news and weather channels to see how likely it was that she would be waved off the following morning. Flipping to MSNBC, I hoped that entry fireball was stock footage from the space station Mir.

1 February 2003: 18:07 Mountain Standard Time. I had to get out of the house fast; my room mate was the most insensitive person I had ever had any sort of lengthly relationship with. By the time I got out, I knew as much as that sensors were lost in the left wing prior to loss of signal. After Columbia Project was not to be about the disaster itself:

2 February 2003: 11:00 Approx. Mountain Standard Time, 28 hours after the loss of Columbia on her final voyage. The question occurs to me, "What if the investigation board recommends that the Shuttle never fly again?" It took me about two minutes to found After Columbia Project specifically to answer that question. I race to the library to establish and take out the Shuttle Book by Dennis Jenkins (actually, Space Shuttle: The History of Developing the National Space Transportation System, Motorbooks 1989, first edition...not counting the little Aerograph. The current version, my library didn't have, is Space Shuttle: The History of the National Space Transportation System: The First 100 Missions, Voyageur 2001, 3rd Ed.)

April 2004 to November 2005: Orbiter Mars Direct Project. We found out that Mars Direct had a lot of problems, and tried to fix them while sticking with the Mars Direct architecture, including the Ares launch vehicle. Today, I call this booster the Baker-Zubrin Ares, since NASA has poached the name for Constellation boosters. David Baker originally designed it, at Robert Zubrin's request, in 1990. It was a Shuttle Derived Booster, and bears a passing resemblance to Ares V of Constellation. We added a separate crew ferry, since Mars Direct had no Earth launch abort capability. The only real crew spacecraft to be as weak with regards to crew safety is the Voskhod...the first one, not Voskhod II, which was slightly safer if something went wrong.

November 2005 to June 2006: I concentrate my efforts on a booster concept called Greenstar...a "Big Dumb Booster." I discover the "total thrust pressure" problem which discredits a lot of the Big Dumb Booster camp's thinking. is the basic text on low cost boosters. The implication of the total thrust pressure problem is that, beyond a certain size, approximately equivalent to 20 tonnes of LEO payload (Ariane V, Proton, Delta IV Heavy, Atlas V HLV...the biggest commercial boosters), the cheapest boosters will have turbopumps to generate enough thrust to get them off the pad. Greenstar unwittingly crossed that threshold without them and faced its fate...its designer (me), was forced to admit that he had a dud on his hands, and thus abandoned the project. Most of LEO On The Cheap is still perfectly valid.

June 2006 to November 2006: Mars Challenger. This was my sample return mission entry to MarsDrive ( Consortium's Sample Return Design Contest. In May of 2006, Grant Bonin begins the lineage of MarsDrive human mission designs with a [semi-]solo effort published as Mars For Less. In this design, the Mars Direct elements are launched with boosters only large enough to launch them to LEO, 25 tonnes at a time. Each of the two elements (Earth Return Vehicle and Surface Hab) requires two launches, which are assembled on LEO. Each element requires an initial four launches for small oxyhydrogen Proteus maneuver stages. Instead of Mars Direct, which requires 2 huge launches, you have Mars For Less, which requires 12 launches on existing boosters.

February 2007 to April 2007: Mars Challenger II. This development of the sample return mission was similar to the original. Mars Challenger (both) launch two landed elements in two different landers on the same Atlas V 541 booster. They separate just before entering Mars' atmosphere. The more detailed one is the Judith Booster, which launches the samples to Earth. The other, expected to gain more public attention, is the Christa Rover, which looks for and examine samples. The strategy for protecting Earth from potential dormant nasty germs is to examine and experiment with samples to make sure they don't have any biological responses in an Earth like environment. This includes most of the experiments of Viking, a few from Phoenix, and polymerase chain reaction, which looks for DNA. "DNA fingerprinting" by police investigators is the usual application of polymerase chain reaction.

May 2007: The beginning of After Columbia Mars Direction, titled Mars For WAY Less. In a couple of weeks, it becomes MarsDrive Mission, MarsDrive Consortium's new official architecture. During Mars Challenger, I discovered about how to land on Mars, and how much of a pain it was. I concluded quickly that the large elements of Mars Direct were not going to work because they were too large to land without massive development effort. My proposal was to work with smaller landers.

June 2007: MarsDrive Mission begins to take shape, with inflatable habitats both in space and on the surface of Mars, two small boosters to return the entire crew of six (if one can't be used, the other can accomodate all six, if stripped down and without a sample payload; normally each booster launches three crew members.) Two rovers, with three crew members in each. The crew actually land in their rovers and can then easily rove about exploring the environment and bringing supplies from the other small landers together into a base.

July-August 2007: Ron Cordes shows up, presents his fairly weak credentials as an ex-NASA propulsion engineer (late 1960s, Marshall Spaceflight Center. I guessed his experience very accurately based on his opinions.) It takes just ten days after his arrival before problems start developing between us. Ron Cordes is appointed the design team leader, and promptly throws out the entire MarsDrive Mission, working instead on his own Design Reference Mission, which is basically a sized down version of what NASA has planned, not a significantly new development. MarsDrive Mission changes to After Columbia Mars Direction.

September 2007: Frank Stratford, founder and business leader of the MarsDrive sends me an email which indicates that he has completely misunderstood me, and has completely the wrong idea about what certain attitudes that I have. In reality, I am receptive to criticism, and attempt to answer them as validly as possible. When I'm wrong, I apologize. When I'm right, most people understand and agree. Somethings are harder, such as Lilmax, the 50 tonne class low cost booster replacing Greenstar. It has turbopumps. I work out the problems with Frank, and life goes on...not so happily...not so ever after.

October 2008: Every useful post of mine was punctuated by a tiring and useless flame war, by Ron, designed to deflect the concern of my question, objection, suggestion, or solution concept from his design to anything other than his design, be it objections to my solution (usually because his element is too good to require consideration of anything else), my personal credentials, the fact that I didn't do aerothermal performance analysis with 3D CFD, etc.. Often (not always) his compaint about me personally had nothing to do with the mission. Frank decides we should make colonization our primary objective. Realizing how expensive and nearly impossible such a mission model will be with today's boosters, I start strongly advertizing Lilmax as a solution to the booster procurement problem. Lilmax, as a minimum cost booster using simpler manufacturing techniques, technologies, and materials, is open to bid by a much larger variety of contractors, including many naval contractors and steel fabricators. Derivative boosters (likely to incorporate more cost savings measures with Lilmax present on the field of competition) are not rulled out. After 16 months of disorganized and sporadic discussion on Ron's design, Ron quits, and the Design Reference Mission loses its leader.

1 November 2008: MarsDrive and After Columbia part ways permanently after Frank repeats the feat of September 2008, this time sharing his otherwise private email with another group member. Add to the completely inaccurate observations about my personality and the relative support I have for various elements and concepts, he issues Order 66: Drop Lilmax, or we'll stop everything until you do. The discussion enjoyed eleven (11) days of freedom. During this period, After Columbia Mars Direction had become Mars Bounty, which I didn't refer to often. Upon my resignation, I decided to move After Columbia Mars Direction here.

The Elements:

Stampede Lander: Relatively small as a human mission lander, it lands 6000kg of useful payload on the surface of Mars, and masses 12000kg at entry, or 14000kg at launch from Earth. The booster requires about 40,000kg of equivalent LEO performance.

Destiny Booster: The small booster rises from Mars' surface to orbit above Mars, where it rendezvous with the Earth Return Vehicle. It generates its own propellants on Mars, liquid oxygen and ethylene ("oxyethylene"). If colonization is successful, it would return nothing but samples, or people who decided to come back. It can accomodate up to three crew members comfortably, or six in an emergency.

Maneuver Stage: The ACMD architecture assembles on a highly eliptical earth orbit of 24 hours (although libration orbits have not been ruled out) in order to get it away from the thermal radiation of Earth. With a sunshade, oxyethylene propellants can freeze, but hydrogen will still boil. The high elliptical orbit allows the modern booster to launch closer to the type of orbit it was designed for. It also nearly eliminates the departure stage, hence Maneuver Stage, which may also be used for Mars orbital insertion, and departure from Mars orbit to come back to Earth. The high assembly orbit was suggested by Grant Bonin. Since his study Mars For Less, relies on a low assembly orbit, this suggestion, and its remarkable practicality, shows his humility and flexibility. I wish I could work with him.

Sprint Crew Ferry: A simple craft for launching the crew from Earth to the assembly orbit. Several current designs may qualify with little or no modification. SpaceX Dragon is the current front runner. It's command module will form the Earth Descent Vehicle.

Lilmax Earth Booster: Lilmax itself is a minimum cost booster, however the Atlas V derivative (Evolution Phase 1: Wide Body Centaur, which I call Atlas VI 52H) has the required performance, and is the front runner for the architecture's Earth booster. There are lots of good reasons to persue Lilmax, since it can open the field of competition to non-aerospace contractors (for fabrication of its much simpler parts, the use of shipyard facilities, and possibly those that produce industrial ASME rated pressure vessels and ordinary shipping containers.) Lilmax, taken from the perspective of reducing costs, is likely to drive down the prices of the big aerospace contractors, even if it can't be implemented as Lilmax, per se.

Surface Hab: a multipurpose inflatable stucture for use on the surface of Mars. It can be living quarters, shop, lab, greenhouse, etc.

Cruise Hab: The inflatable module the crew lives in during the several months of cruise between Earth and Mars...except during solar flares, when they hunker into the attached Rover or Earth Descent Vehicle.

Crew Rover: The crew land in threes on the surface of Mars, in their rovers, using the Stampede Lander. Each Crew Rover weighs 6000kg.

Supply Trailer: These are wheeled packages landed on Mars, and capable of being "towed" by the Crew Rover (an electrical cable provides power for the Supply Trailer wheel motors, which is a more flexible idea than a also provides spares for the Crew Rover.

The Organization:

The basic engineering problems of getting humans to Mars can be made to fit under one of three very large umbrella departments. Some are responsible for entire elements, although in many cases, there will be two or three departments working on a single element.

Mars Access Plan (MAP): Getting from the surface of the Earth, to the surface of Mars, and back...and everywhere in between. MAP's jurisdiction includes most of the Destiny Booster, all of the Maneuver Stage, Stampede Lander, Earth Descent Vehicle, Sprint Crew Ferry and Lilmax Earth Booster. MAP would be the organization to trade assembly orbits with libration points, consider solar or nuclear propulsion,

Mars Settlement: Working on the surface of Mars. They dominate the Crew Rovers, Shops, Labs, and initially, Greenhouses.

Crew Health: Living on the surface of Mars, deep space, and during transitional periods. Crew Health affects all elements that carry crew members, but dominates those elements where crew life support is a primary function. The Habs (Cruise and Surface), and share with Mars Settlement, some of the supply trailers, depending on what they carry. The Greenhouses, while experimental, are the pervue of Mars Settlement, but they cooperate with Crew Health on developing and meeting the goals of the Closed Ecological Life Support System (CELSS). Once operational, the Greenhouse becomes a Crew Health item. During the design phase, they will work closely together, but I'm expecting Crew Health to have more input. Crew Health's main and most nettlesome job will be to figure out how to attain and maintain crew hormesis (ongoing sustained health) in the high radiation, microgravity environment of space with food, supplements, medicines and medical equipment that may have been in storage for up to four years.

And that huge post concludes the introduction to the After Columbia Mars Direction.