Smallest Human Ascent or Descent Lander for Mars Or Earth

RobertDyck · 2015-03-22 09:44:03

kbd512 keeps claiming that single person entry vehicles will be light, while multi-person vehicles will be heavy. But let's not forget, the area of metal for the capsule hull. Let me use a cube to illustrate the point. A single cube 2m x 2m x 2m will have 6 sides, each 2m x 2m = 4m^2. With six sides that will be 6 x 4m^2 = 24m^2. If you divide that into 8 cubes, each 1m x 1m x 1m, then the outer faces will be exposed sides, but now you expose inner surfaces as well. The face of each cube is 1m x 1m = 1m^2, so each smaller cube has 6 x 1m^2 = 6m^2 surface area. But with 8 such cubes to enclose the same total volume, you now have 8 x 6m^2 = 48m^2. Again the reason you have twice the surface area to enclose the same volume, is the faces exposed by the cuts.

To enclose 4 astronauts you require a given volume for their bodies plus spacesuits. And a given mass for their bodies plus spacesuits. And a given mass of life support, either bottled oxygen plus lithium hydroxide, or if you use the Russian system a given mass of potassium superoxide. Enclosing that in a spacecraft hull requires a given surface area, which must be able to withstand the heat of atmospheric entry. Dividing that into 4 small capsules instead of a single large one, means more total surface area. That means more mass, so more heat shield and more parachute area to support that mass. A single vehicle can use a single guidance computer, single set of inertial sensors, and single radio, but with separate capsules each capsule needs its own.

Bottom line: separate capsules will always mass more than a single shared capsule.

The mistake kbd512 keeps making is the assumption that the single capsule will have additional equipment, while single capsules will not. That is comparing apples to oranges. You can only compare apples to apples, which means a single capsule designed for atmospheric entry only, to separate capsules for the same purpose. When you do that, the single vehicle always has lower total mass.

kbd512 keeps complaining about money wasted on something that will never be used. But his single capsules are just that, will never be used. I have tried to appease him by suggesting a minimum-mass/minimum cost emergency bail-out kit. That would be MOOSE. But he keeps obsessing about single atmospheric capsules.

Let me put it another way. For Mars, landing is not everything. You have to look at the whole system. How will you get astronauts off Mars, back into space? How will you get fuel to the Earth Return Vehicle? Will your ERV launch from Mars surface or Mars orbit? Either way, how do you fuel it? Are you arguing to bring fuel for return all the way from Earth? If so, how much additional fuel do you need to launch that fuel from Earth? So it's not just return propellant, it's also propellant needed to deliver that. When you add up everything, what is the total mass that has to be launched from the surface of Earth to get astronauts from Earth to Mars and back to Earth?

kbd512 · 2015-03-22 11:09:14

RobertDyck wrote:

kbd512 keeps claiming that single person entry vehicles will be light, while multi-person vehicles will be heavy. But let's not forget, the area of metal for the capsule hull. Let me use a cube to illustrate the point. A single cube 2m x 2m x 2m will have 6 sides, each 2m x 2m = 4m^2. With six sides that will be 6 x 4m^2 = 24m^2. If you divide that into 8 cubes, each 1m x 1m x 1m, then the outer faces will be exposed sides, but now you expose inner surfaces as well. The face of each cube is 1m x 1m = 1m^2, so each smaller cube has 6 x 1m^2 = 6m^2 surface area. But with 8 such cubes to enclose the same total volume, you now have 8 x 6m^2 = 48m^2. Again the reason you have twice the surface area to enclose the same volume, is the faces exposed by the cuts.
To enclose 4 astronauts you require a given volume for their bodies plus spacesuits. And a given mass for their bodies plus spacesuits. And a given mass of life support, either bottled oxygen plus lithium hydroxide, or if you use the Russian system a given mass of potassium superoxide. Enclosing that in a spacecraft hull requires a given surface area, which must be able to withstand the heat of atmospheric entry. Dividing that into 4 small capsules instead of a single large one, means more total surface area. That means more mass, so more heat shield and more parachute area to support that mass. A single vehicle can use a single guidance computer, single set of inertial sensors, and single radio, but with separate capsules each capsule needs its own.
Bottom line: separate capsules will always mass more than a single shared capsule.

How much more?

RobertDyck wrote:

The mistake kbd512 keeps making is the assumption that the single capsule will have additional equipment, while single capsules will not. That is comparing apples to oranges. You can only compare apples to apples, which means a single capsule designed for atmospheric entry only, to separate capsules for the same purpose. When you do that, the single vehicle always has lower total mass.

Have you seen a multi-person capsule design that didn't include the kitchen sink in the design?

RobertDyck wrote:

kbd512 keeps complaining about money wasted on something that will never be used. But his single capsules are just that, will never be used. I have tried to appease him by suggesting a minimum-mass/minimum cost emergency bail-out kit. That would be MOOSE. But he keeps obsessing about single atmospheric capsules.

Whereas a multi-person capsule that there isn't funding to develop will be used?

What you proposed was akin to a Redbull stunt. NASA is never going to permit astronauts to free fall to Mars encased in high temp styrofoam. I'm talking about a real capsule system, just not one laden with every conceivable survival aid.

RobertDyck wrote:

Let me put it another way. For Mars, landing is not everything. You have to look at the whole system. How will you get astronauts off Mars, back into space? How will you get fuel to the Earth Return Vehicle? Will your ERV launch from Mars surface or Mars orbit? Either way, how do you fuel it? Are you arguing to bring fuel for return all the way from Earth? If so, how much additional fuel do you need to launch that fuel from Earth? So it's not just return propellant, it's also propellant needed to deliver that. When you add up everything, what is the total mass that has to be launched from the surface of Earth to get astronauts from Earth to Mars and back to Earth?

So, should we kill the entire crew in one go if some $2 part that costs $200 fails or perhaps just one crew member?

kbd512 · 2015-03-22 11:20:58

Rob,

One last point. In the real world, any time you put all your eggs in one basket, you naturally become more protective of that basket. The same principle applies to NASA engineering. There's a reason multi-person vehicles have triple and even quadruple redundant systems and days or weeks of supplies. The engineers are concerned with killing everyone aboard because some stupid little part failed. Any multi-person lander is necessarily going to be built using different design criteria from a single person lander. It doesn't have to be that way, but it will be that way. You and I both know that.

RobertDyck · 2015-03-22 11:35:46

kbd512 wrote:

Have you seen a multi-person capsule design that didn't include the kitchen sink in the design?

kbd512 wrote:

Whereas a multi-person capsule that there isn't funding to develop will be used?

Poor sentence structure. But we all agree Orion is a waste of money. It has only one purpose: an Apollo style mission to the Moon. Cancelling that would free funds for other things. However, we saw with Shuttle that cancelling a major project could result it getting nothing.

kbd512 wrote:

What you proposed was akin to a Redbull stunt. NASA is never going to permit astronauts to free fall to Mars encased in high temp styrofoam.

And a single person capsule will never be used for Mars. Landing at some random location, thousands of km from base with no life support, results in the astronaut being just as dead. Any backup is required actually keep astronauts alive. The only conceivable use for a single person entry vehicle is from LEO. MOOSE was designed as a means to bail-out from orbit. It's a backup in case a spacecraft fails, such as heat shield tiles of Columbia. One reason mission control didn't order an astronaut to go outside and inspect before returning, was there was nothing they could do. Mission control commander hoped he could risk atmospheric entry, inspect the orbiter once on the ground. Video spotted something come off the orbiter during launch, and personnel found pieces of reinforced carbon-carbon on the ground. I could describe a rescue with a second Shuttle orbiter, but he chose not to. He gambled, but 7 astronauts on the orbiter are the ones who lost. If a Shuttle orbiter had a bail-out system, then perhaps they would take the care to actually look. Today Shuttle isn't operating, but we have astronauts on ISS. It would be a safety system. But again, that's the only purpose for a single person vehicle.

kbd512 wrote:

So, should we kill the entire crew in one go if some $2 part that costs $200 fails or perhaps just one crew member?

Try finding ways to return astronauts to Earth alive, rather than elaborate ways to kill them.

kbd512 · 2015-03-22 12:03:35

RobertDyck wrote:

Poor sentence structure. But we all agree Orion is a waste of money. It has only one purpose: an Apollo style mission to the Moon. Cancelling that would free funds for other things. However, we saw with Shuttle that cancelling a major project could result it getting nothing.

Now you're critiquing my grammar? Get real. Anyhow, let's revisit your last point about weight. You're pretty much proving my point about which concept would weigh less. We have Dragon and we will have Dragon Rider. Both of those capsules are far more reasonable in terms of weight than any Orion derivative ever will be. Dragon, a capsule without systems required for human use, weighs 4.2t. Dragon Rider won't be lighter.

RobertDyck wrote:

And a single person capsule will never be used for Mars. Landing at some random location, thousands of km from base with no life support, results in the astronaut being just as dead. Any backup is required actually keep astronauts alive. The only conceivable use for a single person entry vehicle is from LEO. MOOSE was designed as a means to bail-out from orbit. It's a backup in case a spacecraft fails, such as heat shield tiles of Columbia. One reason mission control didn't order an astronaut to go outside and inspect before returning, was there was nothing they could do. Mission control commander hoped he could risk atmospheric entry, inspect the orbiter once on the ground. Video spotted something come off the orbiter during launch, and personnel found pieces of reinforced carbon-carbon on the ground. I could describe a rescue with a second Shuttle orbiter, but he chose not to. He gambled, but 7 astronauts on the orbiter are the ones who lost. If a Shuttle orbiter had a bail-out system, then perhaps they would take the care to actually look. Today Shuttle isn't operating, but we have astronauts on ISS. It would be a safety system. But again, that's the only purpose for a single person vehicle.

Why won't a single person capsule be used at Mars? Multiple backups are always nice to have, but if a pressure suit fails then the result is generally a dead astronaut. Should we require astronauts to use two suits, just to be sure we won't have a failure, or accept that space flight carries risks with it? What risks do single person capsules incur that multi-person capsules don't? You wanted to compare apples to apples, so let's do that. If a multi-person capsule that's carrying 30 days of supplies for four people lands significantly off-target, are the astronauts going to make it back to the habitat module? Probably not without a rover. I've already stated why we can't have a gold plated solution to every problem. Whether single or multi-person, the capsules are being used to accomplish the exact same thing.

RobertDyck wrote:

Try finding ways to return astronauts to Earth alive, rather than elaborate ways to kill them.

That is precisely what I am doing, Rob. If you land off target on Mars, then unless you have a fully fueled ascent vehicle, you're probably going to die. The problem with the fully fueled ascent vehicle is mass. Even if EDL with any weight class vehicle was no problem whatsoever, launch costs still drive what we can and can't afford to launch.

RobertDyck · 2015-03-22 12:23:00

Dry mass of Dragon is what you listed. With full propellant tanks, it's 8.0 metric tonnes. Compare that to Orion: 28.0t with full propellant tanks, fairing around the service module, and Launch Abort System.

In the discussion thread Light weight nuclear reactor, updating Mars Direct, I described using Dragon as the ERV capsule. Orion is way too heavy. So we're actually in agreement. The only difference is your solution to Orion is to design something new from scratch. My solution is Dragon.

Grammar? None of us are English majors. I'm just not sure I understand what you wrote.

Multiple backups are generally good. But you have to look at how your backup will work. How would a single person capsule be used? Abort to the surface would leave an astronaut thousand of km away; possibly the other side of Mars. No habitat, no ascent vehicle. How long can you live in a suit?

GW Johnson · 2015-03-22 13:38:13

Single or multiple person, bailout from LEO is entirely different from any sort of abort bailout at Mars. A capsule suitable for LEO would be too heavy for Mars, and any Mars bailout capsule is going to need more post-landing life support than anything you might use here.

Here, all you have to do is not-crash, then get the hatch open. You'll need a raft on the water. Land or water, you need a bit of drinking water and some sort of radio beacon so somebody can come get you before you starve. That's hours to at most a day or two today.

On Mars, there is a serious post-landing life support issue to deal with, and a stranded-astronaut retrieval issue to deal with. And the entry and landing systems requirements are entirely different on Mars. Further, if your mission is so minimalist in its design that no rescue bird is available, then there is no point to bailout capability, either ascent or descent. What would be the point? Dead is dead.

On the assumption that rescue vehicles really are available, then your bailout capsule will need several days' worth of water, oxygen, and food per person, perhaps even a couple of weeks' worth. It's got to have propellants for the propulsive part of landing. It'll need a minimal heat shield, but not as much as we need here. For one-shot use, the lateral outer shell can be bare metal. If it's only one-man and under about a ton, you might use a chute. Anything bigger would be better off at Mars going straight to retro-propulsion upon end-of-hypersonics. That is why the proposed Dragon variants for landing on Mars don't use chutes - the manned version doesn't even use chutes here, except as a backup. At Mars, Dragon would only need of a lighter, thinner heat shield, and nothing laterally, really.

Here's the kicker: rescue vehicles. That basic capability does not fit most minimum-mass mission designs, and it never will. Doesn't matter whether you base it from LMO or on the surface, you still have to send it there. But, if you have rescue vehicles, you are morally bound to provide that bailout capability! Technical issues get overridden by that obligation.

That being said, here's my question: why not make whatever you use for a bailout capsule do double duty? Why send dedicated bailout mass to Mars if it serves no other function?

Whatever these lander vehicles are (concepts vary from mission design to mission design), I'd use some variant of manned Dragon as the vehicle's crew/control cabin. Everybody rides there for the trip (down or up). If there's an accident requiring bailout, use the retropropulsive Dragon for the abort bailout landing. Otherwise, make that mass serve other needs, too.

GW

SpaceNut · 2015-03-22 13:45:57

The current landing ability sure would be nice if its scaleable to get such as the Dragon as designed to Mars surface but its multiple decades away.
So until we can lets look at down scaling the designs to what we know works and apply it to a sortie mission.

kbd512 · 2015-03-22 13:46:05

RobertDyck wrote:

Dry mass of Dragon is what you listed. With full propellant tanks, it's 8.0 metric tonnes. Compare that to Orion: 28.0t with full propellant tanks, fairing around the service module, and Launch Abort System.

The capsules I proposed won't weigh more than 1t. In your opinion, would 4t for backup capsules of extremely simple design be worth their weight on a mission? Dragon Rider is nowhere near completion of development for a Mars landing, so would it be fair to say that we're going to spend quite a bit of money irrespective of whether or not we design a one person capsule from scratch or develop Dragon Rider to the point where it can reliably land on Mars?

RobertDyck wrote:

In the discussion thread Light weight nuclear reactor, updating Mars Direct, I described using Dragon as the ERV capsule. Orion is way too heavy. So we're actually in agreement. The only difference is your solution to Orion is to design something new from scratch. My solution is Dragon.

As previously noted, Dragon Rider would require at least one unmanned test on Mars. How many one person capsules can we reasonably afford to test on Mars in comparison to four or six person capsules?

RobertDyck wrote:

Grammar? None of us are English majors. I'm just not sure I understand what you wrote.

RobertDyck wrote:

Poor sentence structure.

RobertDyck wrote:

Multiple backups are generally good. But you have to look at how your backup will work. How would a single person capsule be used? Abort to the surface would leave an astronaut thousand of km away; possibly the other side of Mars. No habitat, no ascent vehicle. How long can you live in a suit?

A single person capsule will be used the same way a multi-person capsule will be used. In either case, the capsule has to land with precision near the habitat module on Mars. We can afford more testing of single person capsules to ensure that the capsules land exactly where intended.

If you're nowhere near your habitat module and you don't have a fully fueled ascent vehicle, then you're dead. The number of corpses per capsule is irrelevant. I've already gone over that at some length. Some things you just have to accomplish, period, or you don't come home. Loading a multi-person capsule with weeks of supplies and a rover will only ensure that it becomes exactly what Orion is- too damn heavy to easily land or send to Mars in the first place.

We seem to have conceptual disagreement about what a lander is supposed to be. To my way of thinking, a lander is supposed to get you to the surface of Mars, not serve as a lifeboat or a habitat module or attempt to account for all possible contingency scenarios. If you want to come home, you properly test things ahead of time and train your astronauts appropriately. That's somewhat easier to do when the hardware is smaller and lighter.

In six years in the Navy, I never walked around any of the ships I served on with a life preserver unless I was on the flight deck and we were conducting flight ops. I learned how to swim in the ocean and how to jump off moving platforms long before I ever joined the Navy, something that's proven far more useful than running around with a life preserver on anytime I'm near the water. In rare instances a few people fell overboard or were blown overboard and far fewer still drowned. Many, many others, including myself, lived. The point is, everything in life is a risk and most actions to counter risk involve trades. Are the trade-offs for using heavy multi-person capsules that may take a decade or more to properly test worth the expense and opportunities lost?

SpaceNut · 2015-03-22 15:59:37

GW Johnson, kbd512, RobertDyck; the point is well taken that if we miss the landing with anything but a simple short walk to the supplies and habitat that any crew attempting to land on Mars is dead very shortly indeed regardless of the ship we land in or if we land them all in the same lander.

So we have hit on a demonstrator mission that is a must before men go to Mars, in pin "point landing" with different launches and deorbits to the same location.

We have also hit on the mars landing importance of preloaded consumables at the landing site awaiting the crew which could be done in conjunction with the demonstrator mission as if not sucessful we would still know where to find a supply cache on a manned mission that lands in the ballpark of the demonstrators landing site location. It should be Water, dry food, fuel and oxygen for the what if senerio.

kbd512 · 2015-03-22 16:26:51

Maybe a better potential solution to the landing precision issue is to litter general landing areas with supplies so that even if you're 50 to 100 klicks off target you still have air, water, and fuel (if we land dirt bikes or rovers). Each supply cache would have a beacon, as would the habitat modules and rovers. If you can't land within 100 km of the habitat, Mother Nature permanently revokes your pilot's license. As previously stated, some things you just have to do correctly.

SpaceNut · 2015-03-22 20:25:11

Thats sort of why I wanted to get some data from the ISS for cargo resupplies as that could be used to decide how much to bundle into each lander but its seems that the data is a bit skewed as there is lots missing....

RobertDyck · 2015-03-22 21:45:20

Scatter the entire planet? Let me recommend some reading. Two editions, pick one:

The Case for Mars: The Plan to Settle the Red Planet and Why We Must - 2011

The Case for Mars: The Plan to Settle the Red Planet and Why We Must - 1997

Cargo landers can be useful, but to deliver cargo to your one base location. Mars is a big planet. I live in western Canada. We know what wilderness is like here. I live in Winnipeg; I consider it a big city. Including bedroom communities, the greater Winnipeg area has 700,000 people. But it's a big city surrounded by miles and miles of nothing but miles and miles. The second largest city in the province is Brandon, population 36,000 and 3 hour drive away. To the south Fargo, North Dakota, has a population of 100,000 and 4 hour drive away. Regina is the largest city in the province of Saskatchewan, the next province west. Regina has a population of 190,000 and a little over 4 hours drive away. The closest large city is Minneapolis, MN, population similar to Winnipeg, a little over 7 hour drive plus about an hour for the border crossing. The closest large city within Canada is Calgary, about a million people and 14 hour drive away. You can drive for hours without seeing any town. South has farms, but there are no farm houses. Farmers live in towns and commute to their fields. Farmland is allocated in quarter sections; a section is a mile by a mile. Large farms consist of multiple sections. But just a half hour drive north or east of Winnipeg, there aren't even farms; just highway and trees and lakes. A friend used to take me to his cottage on Beresford Lake. You don't want your vehicle to break down there. Gravel road, no electricity, no internet or WiFi, no cell phone service, no telephone. His cottage has a solar panel, wood stove for heat, draws lake water for washing, and large jugs of drinking water. He takes a boat to a hand pump well on the other side of the lake. If a vehicle breaks down there, you better be able to fix it yourself. The tiny town of Bisset is about 50km drive by gravel road. North of Bisset is land without even a dirt road. English Brook is northwest of Bisset, but from English Brook to Norway House is over 300km without a road of any kind. And this is Earth. Mars doesn't even have air to breathe. You expect close access to supplies on Mars?

Last edited by RobertDyck (2015-03-24 11:31:48)

kbd512 · 2015-03-22 23:22:17

Rob,

I expect that we can land within 50 km of a landing beacon and closer than 10 km in all probability, a figure that's generally accepted by JPL as what we're currently capable of. If we can't land within 10km of a target, then we probably shouldn't send humans to Mars. Curiosity landed 2.4 km from its intended target and Opportunity landed 2.32 km from its intended target. That's pretty good, but still not good enough. I have no idea how close Pathfinder landed to its intended target. Our accuracy target is 1 km or less, with .5 km being the goal. That's JPL's idea of a precision landing.

With surface radio beacons and perhaps a GPS constellation (something Mr. Musk wanted, if that ever proves feasible), I think we can lick the landing precision problem. We also need a high precision surface map, like that provided by MGS, for terrain avoidance. I'm aware of what MGS and MRO provided, but I want confirmation using a second source or multiple sources. If we have a GPS constellation at Mars, laser altimeters on those satellites should also continually map the surface. It's simpler and easier to use high precision maps and have systems that indicate precisely where you are, relative to a point on the surface or other satellites, rather than trying to incorporate a reliable terrain avoidance radar system into the landing avionics. Terrain avoidance radar would not be doable for a micro capsule with the mass constraints I have set for it, but it would be doable for a larger multi-person lander like Red Dragon.

I do not wish to abandon the use of multi-person landers stocked with supplies and perhaps a rover as the preferred method for landing humans on Mars.

SpaceNut · 2015-03-23 18:12:58

That said packaging in some sort of low tech transporting a suited crewmember would be a must unless we can garantee landing within 500m from the rest of the crews supplies and habitat as the limiting factor is the suits capability to support life.

I posted a thought about making a vehicle engine run by fuel injection of hydrogel fuels into a ICE engine, what do you think reply in the other topic please.

Forgot to post the topic....
Manned Rover ...something... for the engine...

kbd512 · 2015-03-23 23:40:09

SpaceNut wrote:

That said packaging in some sort of low tech transporting a suited crewmember would be a must unless we can garantee landing within 500m from the rest of the crews supplies and habitat as the limiting factor is the suits capability to support life.
I posted a thought about making a vehicle engine run by fuel injection of hydrogel fuels into a ICE engine, what do you think reply in the other topic please.

My take on small powered vehicles like dirt bikes or rovers is that while they could prove quite useful for contingency purposes, they add lots of mass. Sending the first astronaut down in a micro capsule to retrieve the mobile habitat gives the rest of the astronauts a much better chance at being rescued should one or some of the capsules miss the intended target. If you're the first one on Mars, you're taking a calculated risk. Everything could work perfectly, or your friends may bury you there. In short, I favor a phased landing approach that doesn't run the risk of killing the entire crew in one go.

Perhaps it'd be better to simply send two extra oxygen bottles and a small pedal powered bike with the astronauts rather than a chemically powered vehicle. Everyone here seems to have the same complexity cravings that NASA has. Keep it small and simple.

SpaceNut · 2015-03-24 18:50:17

I do not want to get this topic any further off as we have the past topic to dicuss this in with a greater level of reasonable detail.

Bikes on Mars? - Don't laugh!
Bikes
MotorBikes

I will post one one of them...

kbd512 · 2015-03-24 20:17:48

The Montanara Volta weighs just 9 kg and uses an electric motor to assist the rider.

https://www.electricbike.com/lightest-bike/

In contrast, some of the lightest gas powered bikes weigh more than 59 kg.

http://www.fxbikes.com

Is the gas powered bike worth the extra 50 kg? It's certainly much faster than the pedal powered bike, until it runs out of fuel. Should astronauts travel around on Mars at 30+ km/h wearing thin pressure suits? Probably not smart.

For comparison purposes, a high performance electric bike like the BRD RedShift weighs 114 kg.

If you can't go to the habitat module on Mars by foot or pedaling, then perhaps the habitat should be mobile and come to you.

kbd512 · 2015-03-24 20:19:34

SpaceNut wrote:

I do not want to get this topic any further off as we have the past topic to dicuss this in with a greater level of reasonable detail.
Bikes on Mars? - Don't laugh!
Bikes
MotorBikes
I will post one one of them...

I think small powered vehicles are a total waste of mass, time, and effort. The habitat module should be mobile and come to you after you land.

GW Johnson · 2015-03-26 15:40:54

All this discussion about bikes and other surface transportation is driven by the estimate I saw earlier of a 10 km error in landing accuracy. That's a landing accuracy for a probe flying "blind" toward intended geographic coordinates. That's what we've demonstrated so far. It is completely unacceptable for sending men to Mars, unless only one single vehicle lands at every single site you visit.

But consider also this: once the very first craft lands within 10 km of where we intend it to be, it can deploy a radar transponder to guide down subsequent vehicles. Subsequent craft to that site can home-in on that transponder, if you don't "squeeze the turnip for too much blood" in terms of propellant. This is nothing but missile intercept technology, and the typical miss distances in that arena range from 1 to 10 meters. Meters! Screw the kilometers! We need METERS here for this multiple-vehicle Mars landing stuff!

The signal-detection ranges for landing on Mars are longer, so the transponder needs to be very powerful. So what? Put the delta vee capability into all the craft you want to land, and thus be able to land them close together! There is NO other way to do that job.

Face up to that ugly little fact of life, and these discussions will prove a lot more fruitful. And don't kid yourself, these discussions on this site are seen by folks at NASA and the others.

That brings up "too close": you don't necessarily have to collide with a previous craft to have a disaster. All you need is "close enough" for rocket blast and thrown debris to cause damage. All that really means is the transponder is on a big landing field away from earlier vehicles, and you'd better have some spares. Powerful transponders will be sort of heavy, guys! Because of the batteries and power supply, if nothing else.

Once down, a whole fleet will have to have some sort of separation distance between each of the vehicles to avoid rocket-blast and thrown-debris damages. So how far is "safe"? WHO THE HELL KNOWS? I haven't seen anything from anyone addressing THAT issue!

Once you figure that out, the next question is: how are you going to transfer "whatever" between them?

If it's propellant, we need to be talking about laying pipes or hoses out along the ground AFTER everything is landed. If it's cargo, we need some sort of loader vehicle to move things. Yep, you really will need some sort of ground vehicles. Period. The more you intend to accomplish while there, the more, and more different types of, ground vehicles we will need.

Once you have vehicles AND propellant production going at some site, then (and ONLY then) do you have a rescue capability in place for errant vehicles and astronauts. UNLESS you choose to base from orbit, of course, AND you have the vehicles and propellant up there.

That needs to be considered from the outset, in the overall mission design. Murphy's Law says bad things WILL happen, and if you don't plan ahead for that, you WILL KILL people.

And when you are thinking your way through these issues, don't forget that no matter what, there is nothing so expensive as a dead crew. It pays long-term NOT to kill people. Another ugly little fact-of-life.

Which is in fact why I have never, and WILL NEVER, believe in "minimum-mass" scenarios for sending men and women to Mars.

If you're gonna go, you must "do it right". "Right" is measured by a crew that returns not just alive, but acceptably healthy. I'm sorry, but that's just an ugly little fact of life at this time in history. Deal with it.

GW

kbd512 · 2015-03-27 00:09:27

GW,

Nobody here wants to get anyone killed. Some other ugly little facts have to be faced, though. There isn't a good solution for every potential problem. In the same way that missing the runway normally results in death and destruction here on Earth, such is the case on Mars. You land where you're supposed to or your odds of survival are slim to none. We've launched over 100 Space Shuttle missions and never lost a single orbiter to pilot error. You get one and only one chance to get it right, which is why older men and women with thousands of hours of flight time in multiple airframes are the only ones permitted to fly it. To channel Chris Costa a little, if you're a professional pilot then you practice landing until you can't get it wrong.

Minimum mass missions don't necessarily make the missions more dangerous to the crew if you're intelligent about what you send to Mars. Even something as simple as the pressure vessel for landing clearly illustrates the problem with all the solutions I've seen from NASA. Nearly every concept attempts to use some novel technology or combination of novel technologies that demonstrate how clever their engineers are as opposed to designing something simple that works or adapting existing technologies for their purposes. Obviously it makes the problem more interesting, but is the goal behind the development work to make the solution intriguing to the engineers and scientists or to use simple and workable solutions that function in the real world where cost and complexity are real problems?

In simplest form, a lander (for humans) is a maneuverable pressure vessel with a thermal protection system. There's no requirement for landing everyone in the same capsule. That's just defense contractors who want big spending programs to collect as much money as possible from the tax payers. I don't care about the spending programs if there's unlimited funding available and we don't care how long the solution takes to develop and test. In the real world, there's no such thing as unlimited funding, so let's pretend for a moment that we have work within the constraints of a rather small budget for the undertaking that NASA says it wants to attempt.

We can make the human EDL solution for Mars as heavy and complicated as is pleasing to us, no doubt producing a whole range of other problems that require solutions of their own, or we can accept that smaller and simpler can and will function just as well as heavier and more complicated in actual operations.

louis · 2015-03-27 04:55:35

I don't see why you are opposed to an Apollo style lander...

It will obviously require some adaptation for the Mars atmosphere but I don't doubt we can get the first colonists to Mars safely using such a lander.

The key is to pre-land all the life support equipment in the landing zone for the long stay - including a hab - which will be available to the crew on landing. We probably need to provide 3-4 days' life support on board the lander.

I am beginning to think it might also make sense to send down an ascent vehicle separately. The fuel can be manufactured in situ.

kbd512 wrote:

GW,
Nobody here wants to get anyone killed. Some other ugly little facts have to be faced, though. There isn't a good solution for every potential problem. In the same way that missing the runway normally results in death and destruction here on Earth, such is the case on Mars. You land where you're supposed to or your odds of survival are slim to none. We've launched over 100 Space Shuttle missions and never lost a single orbiter to pilot error. You get one and only one chance to get it right, which is why older men and women with thousands of hours of flight time in multiple airframes are the only ones permitted to fly it. To channel Chris Costa a little, if you're a professional pilot then you practice landing until you can't get it wrong.
Minimum mass missions don't necessarily make the missions more dangerous to the crew if you're intelligent about what you send to Mars. Even something as simple as the pressure vessel for landing clearly illustrates the problem with all the solutions I've seen from NASA. Nearly every concept attempts to use some novel technology or combination of novel technologies that demonstrate how clever their engineers are as opposed to designing something simple that works or adapting existing technologies for their purposes. Obviously it makes the problem more interesting, but is the goal behind the development work to make the solution intriguing to the engineers and scientists or to use simple and workable solutions that function in the real world where cost and complexity are real problems?
In simplest form, a lander (for humans) is a maneuverable pressure vessel with a thermal protection system. There's no requirement for landing everyone in the same capsule. That's just defense contractors who want big spending programs to collect as much money as possible from the tax payers. I don't care about the spending programs if there's unlimited funding available and we don't care how long the solution takes to develop and test. In the real world, there's no such thing as unlimited funding, so let's pretend for a moment that we have work within the constraints of a rather small budget for the undertaking that NASA says it wants to attempt.
We can make the human EDL solution for Mars as heavy and complicated as is pleasing to us, no doubt producing a whole range of other problems that require solutions of their own, or we can accept that smaller and simpler can and will function just as well as heavier and more complicated in actual operations.

Terraformer · 2015-03-27 05:09:49

Hmmm. If we're using ISPP - which we probably will be - then we're going to have quite a powerful power source by the (pre-landed) hab anyway, so power for a transponder won't be an issue...

RobertDyck · 2015-03-27 06:04:56

Terraformer wrote:

Hmmm. If we're using ISPP - which we probably will be - then we're going to have quite a powerful power source by the (pre-landed) hab anyway, so power for a transponder won't be an issue...

Wha' he said.

And I'm emphasize that point with detail. Mars Direct called for the SP-100 nuclear reactor. That was under development at the time, so the newest, latest, state-of-the-art. It was designed to generate 100kW electric, so Robert Zubrin and his partner assumed the mass could be reduced a bit by reducing power to 85kW. However, when nuclear engineers completed development in 1992, they found a reduced power version would mass exactly the same. So no mass saving. If it's the same mass anyway, why bother spending money modifying the design? Just send the standard design, so the full 100kW. That gives you a little more power. Since then the SAFE-400 reactor was developed; same purpose and also generates 100kW electric. But SAFE-400 was completed in 2007, and has lower mass. Again, don't modify the design, just use the standard one as-is. That gives us plenty of power.

But as Terraformer said, that will leave us with a lot of power. Any reactor has enough nuclear fuel for multiple years. That's necessary for critical mass to get the reactor to work. But ISPP will be finished in a number of months, and will be finished before astronauts leave Earth. So again, plenty of power.

RobertDyck · 2015-03-27 06:56:44

kbd512 wrote:

There's no requirement for landing everyone in the same capsule. That's just defense contractors who want big spending programs to collect as much money as possible from the tax payers.

You keep repeating the same error. Yes, I agree that defence (Canadian spelling) contractors want big spending. Yes, we need to keep cost down. Congress said "No!" to the 90-Day Report because it cost too much. The problem is you keep assuming that splitting a single, shared spacecraft into multiple single-person landers would actually reduce mass. I've explained why it won't.

Let me put it another way. Physics is real life. This isn't some Hollywood movie or TV show. The TV show "Stargate SG-1" showed aliens with technology that looked like ancient Egypt. It's based on the initial premise of the show. A couple episodes showed an escape pod that looked like an Egyptian sarcophagus. Some episodes showed a horizontal sarcophagus as some sort of medical device, other episodes showed a vertical sarcophagus in a Tel'Tak ship as an escape pod. Well, in real life a sarcophagus is a coffin. Just a box to hold a dead body. It isn't an escape pod. In real life an escape pod cannot be a form-fitting coffin-shape. In real life an entry vehicle must deal with high speed atmospheric entry.

Studies by NASA in the 1950s showed a blunt body works much better than a sharp, streamlined vehicle. A blunt body means a round heat shield, and an aeroshell behind it. Wind tunnel studies showed air flow behind the heat shield in a specific pattern. The reason a Mercury spacecraft has the shape it does, is that fits within the wake behind the heat shield. A cone of specific size, with specific angle to the side walls. At a specific distance behind the heat shield, the wake stops collapsing inward, forming a fairly straight cylinder of turbulent air. The nose bit of Mercury, fits within that. Mercury used that to store its parachute, flotation bags, and life raft. And above that was the antenna fairing. But you don't need to use that space. A spacecraft that docks to something, such as ISS, would have a rounded-off, domed top with a docking hatch rather than that nose piece.

NASA shadowgraph:

Notice one of the features of a cone capsule is that the bow shock does not actually touch the heat shield. That reduces heating.

This means a single person spacecraft isn't going to be much smaller than Mercury. You can make electronics smaller, but not much else.

I had already read that Mercury used a titanium alloy; but it turns out Mercury used René 41. Perhaps one of the secrets they wanted to keep from Russia. That alloy is a nickel-chrome alloy using the exact same metals as Inconel 617. The modern alloy has slightly different proportions, 20-24% chrome while René used 18-20% chrome, but pretty much the same. Mercury was an amazing piece of technology. You won't get much smaller.

Notice the size of Mercury vs astronaut body. The only way for a spacecraft to get smaller is MOOSE. That is foam and plastic bag instead of metal capsule. Heat shield is almost the same size, because the astronaut body is the same size. MOOSE is a little smaller because the heat shield doesn't have to support the weight of a metal capsule, or any form of pressure vessel. But you already called MOOSE a Red Bull stunt. If you don't want that, then you're back to Mercury. Modern propellants have a little higher Isp, so a little lower weight than the peroxide oxidizer of Mercury. Electronics are lighter. Life support is the same. I challenge you to find a modern spacesuit as light as a Mercury suit, other than the Russian Sokol. Parachutes have lighter weight material. Do you seriously suggest deleting the reserve chute? That doesn't leave much weight reduction.

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