Musk's plans for Mars

louis · 2016-10-25 15:33:57

SpaceNut wrote:

So with the Red Dragon we could preload any site we would wish on Mars in 10 landers or less and lighten the crewed lander back to a realistic mass for its trip to the surface. So what is in the itemized list of what that 20 tonnes would be?

Here is a list I prepared a while ago for a six person mission (all figures based on some sort of research - not complete guesstimates, but can't provide more back up).

Air locks 2000Kgs
Gas pipes and cylinders 700kgs
Food 1000Kgs
Water 700kgs
Personal hygiene (soap, towels, wipes, shavers, sanitary towels etc) 260Kgs
Water recycling units 500 Kgs
Electrolysis facility 200kgs
Sabatier reaction facility 200kgs
Clothes 180kgs
Space suits 2400kgs
Solar Energy (PV) 3000 kgs
Cabling, electric connections 800kgs
Digger 1000kgs
Three rover trikes 300kgs
Home Habitat 1500kgs
HH Gym equipment 200kgs
Fittings for HH bathroom 300kgs
HH sleep area equipment 350kgs
HH kitchen equipment 350Kgs
Farm Habitat 1000 kgs
Hydroponic equipment 4,200 kgs
Farm tools 200kgs
WorkHab 800 kgs
Solar-electric smelting oven 100kgs
Scaled down machines 600kgs
Tools 50kgs
Storage Hab 400kgs
Medical supplies 250kgs
Mining equipment 300kgs
Electric motors 400 kgs
Batteries 500kgs
Laptops and computer equipment 100kgs
Waste disposal/containers 100kgs
Pyrolysis Unit/vent 200kgs
Communications 300kgs
Miscellaneous 500 kgs
TOTAL 27,430kgs

I think I would now favour a small pressurised rover (which can also serve as a digger) over the rover trikes, which might add 2 tonnes to the overall mission tonnage.

So the concept would be to pre-land most of these supplies to the favoured drop zone in a series of separate missions during a 10 year period in the run up to the landing and then land the humans in the smallest possible "life support" unit. There may be a good argument for making the Rover in effect the human lander payload. Then, rather than having to effect an EVA to get the Home Hab, they could simply drive the Rover into the Home Hab air lock garage and then disembark into a pressurised environment. The idea is of course that the Home Hab would be an automated self inflatable.

Tom Kalbfus · 2016-10-25 15:49:59

Also there is a good argument no to rush everything the colonists will need to live on Mars along with the colonists. Cargo for instance doesn't need to be rushed quickly to Mars so long as it gets there before the colonists so they can use it. What if you wanted to use an ion drive to deliver a massive payload of supplies to Mars, taking several years to get there ahead of the colonists? The slower you go, the more cargo you can bring!

kbd512 · 2016-10-26 14:20:34

Louis and Tom,

There are substantial payload mass fraction advantages using the "slow-boat to Mars" method of cargo delivery, but anything perishable benefits from reduced transit times. Humans, food, and sophisticated computer equipment all qualify as perishable. The faster you can get them out of deep space and onto the surface of Mars, the better. Humans also consume food and water, which requires storage and reprocessing or replenishment. If you can get to Mars in 30 days and come back in 30 days, you need 1/6 as much food and water.

I'm not fixated on getting every piece of hardware needed to land on Mars stuffed into or attached to one vehicle, which is what NASA and MSNW are still fixated on, nor am I fixated on absolute propulsion efficiency. I am fixated on the staggering cost of using super heavy-lift launch vehicles dictated by all-chemical propulsion. It's not feasible with current NASA budgets.

If we can avoid the requirement for SLS class rockets for Mars exploration missions then the entire mission becomes much more affordable, therefore much more likely to occur. NASA won't receive any more funding than it already does. That's a fact everyone needs to accept. It's not a priority for most Americans, our legislature, or our President (even though he says he wants to see humans land on Mars within his lifetime).

GW,

I understand that nobody has a crystal ball and we can't say with 100% certainty that FDR or EMDRIVE will work the way we want it to. However, there is also a very high probability that development of an all-chemical propulsion mission architecture will cost so much that we can't afford to use it. That means one flags-and-footprints mission or no missions at all, which is what we're currently capable of after many years of developing SLS and Orion.

My take on this is that NASA needs to put its money where its mouth is and develop the technologies that enable them to do human space exploration within existing and projected budgets. That means better propulsion technology. Although I may disagree with the man's ideology, I believe President Obama was completely justified when he called on NASA to develop better space propulsion technologies.

louis · 2016-10-26 15:34:32

No, food can last a long, long time. For dried food it can be up to 25-30 years. For tinned food it can be up to 5 years. For frozen, it can be over a year. I imagine vitamin and mineral pills will similarly last a very long time as will some bottled drinks. Water of course should be good for well over a year if properly packaged.

I would simply go with Space X costings for getting stuff to LEO. The Falcon 9 should be able to get over 20 tonnes to orbit (over 8 tonnes to GTO). I think that's enough with orbital assembly to put together a Mars mission over a ten year period. That's another advantage of the mulitiple pre-landings approach: you are not straining to do everything in one year.

kbd512 wrote:

Louis and Tom,
There are substantial payload mass fraction advantages using the "slow-boat to Mars" method of cargo delivery, but anything perishable benefits from reduced transit times. Humans, food, and sophisticated computer equipment all qualify as perishable. The faster you can get them out of deep space and onto the surface of Mars, the better. Humans also consume food and water, which requires storage and reprocessing or replenishment. If you can get to Mars in 30 days and come back in 30 days, you need 1/6 as much food and water.
I'm not fixated on getting every piece of hardware needed to land on Mars stuffed into or attached to one vehicle, which is what NASA and MSNW are still fixated on, nor am I fixated on absolute propulsion efficiency. I am fixated on the staggering cost of using super heavy-lift launch vehicles dictated by all-chemical propulsion. It's not feasible with current NASA budgets.
If we can avoid the requirement for SLS class rockets for Mars exploration missions then the entire mission becomes much more affordable, therefore much more likely to occur. NASA won't receive any more funding than it already does. That's a fact everyone needs to accept. It's not a priority for most Americans, our legislature, or our President (even though he says he wants to see humans land on Mars within his lifetime).
GW,
I understand that nobody has a crystal ball and we can't say with 100% certainty that FDR or EMDRIVE will work the way we want it to. However, there is also a very high probability that development of an all-chemical propulsion mission architecture will cost so much that we can't afford to use it. That means one flags-and-footprints mission or no missions at all, which is what we're currently capable of after many years of developing SLS and Orion.
My take on this is that NASA needs to put its money where its mouth is and develop the technologies that enable them to do human space exploration within existing and projected budgets. That means better propulsion technology. Although I may disagree with the man's ideology, I believe President Obama was completely justified when he called on NASA to develop better space propulsion technologies.

kbd512 · 2016-10-26 16:58:00

louis wrote:

No, food can last a long, long time. For dried food it can be up to 25-30 years. For tinned food it can be up to 5 years. For frozen, it can be over a year. I imagine vitamin and mineral pills will similarly last a very long time as will some bottled drinks. Water of course should be good for well over a year if properly packaged.
I would simply go with Space X costings for getting stuff to LEO. The Falcon 9 should be able to get over 20 tonnes to orbit (over 8 tonnes to GTO). I think that's enough with orbital assembly to put together a Mars mission over a ten year period. That's another advantage of the mulitiple pre-landings approach: you are not straining to do everything in one year.

Louis,

Have you ever eaten five year old MRE's? You won't die, or at least I'm still alive, but it's not particularly appetizing. Food poisoning is not something that comes to mind when I think of having a good time, either. I can't imagine that experience would be any better in space. If you keep the food cold, which should not be particularly difficult in deep space or on Mars, it lasts a lot longer.

Falcon 9 is $62M per launch for 23t to LEO. Falcon Heavy is $100M per launch for 53t to LEO. I'd rather increase the payload by 230% for a 60% cost increase, but that's just me.

We're in agreement about the multiple launch methodology for exploration.

SpaceNut · 2016-10-26 17:04:57

Something else to think of when going to mars fast is the recycling of air, water and waste recovery would not need to be any higher than what we already have for efficiency.

As for the food yes dehydrated will last the duration and then some for surface cargo or for the outgoing or returning legs of any mars mission. Leave the cans and frozen home as its not needed. Plus dehydrate takes up less space and is lots lighter in terms of mass.

louis · 2016-10-26 17:24:26

Well I am envisaging an approx 2 year tour, so no need for food to last any longer than that. Dried potato, dried peas, dried egg and so on are not the greatest food in the world but people can live on them well enough. However I think food provision would take several forms and the dried food may end up being more a fail-safe reserve.

I think even on Mission 1 we should be aiming to grow a range of salad foods on Mars - lettuce, tomatoes, peppers, bean sprouts and so on. Maybe they would supply around 10% of the diet. Apples brought from Earth will last for several months if properly preserved. Then you can have pickled foods, hams and so on.

I wasn't aware they don't have refrigerators on the ISS...is there a particular reason for that? I can't think of one...

kbd512 wrote:

louis wrote:
No, food can last a long, long time. For dried food it can be up to 25-30 years. For tinned food it can be up to 5 years. For frozen, it can be over a year. I imagine vitamin and mineral pills will similarly last a very long time as will some bottled drinks. Water of course should be good for well over a year if properly packaged.
I would simply go with Space X costings for getting stuff to LEO. The Falcon 9 should be able to get over 20 tonnes to orbit (over 8 tonnes to GTO). I think that's enough with orbital assembly to put together a Mars mission over a ten year period. That's another advantage of the mulitiple pre-landings approach: you are not straining to do everything in one year.
Louis,
Have you ever eaten five year old MRE's? You won't die, or at least I'm still alive, but it's not particularly appetizing. Food poisoning is not something that comes to mind when I think of having a good time, either. I can't imagine that experience would be any better in space. If you keep the food cold, which should not be particularly difficult in deep space or on Mars, it lasts a lot longer.
Falcon 9 is $62M per launch for 23t to LEO. Falcon Heavy is $100M per launch for 53t to LEO. I'd rather increase the payload by 230% for a 60% cost increase, but that's just me.
We're in agreement about the multiple launch methodology for exploration.

RobS · 2016-10-26 20:16:22

Here's a plan for a reusable Mars lander: http://www.thespacereview.com/article/3085/1

Like the ITS, it would enter the Martian atmosphere at a 50 degree angle and would land vertically. It would mass 20 tonnes empty, could land 20 tonnes of cargo, could be refueled with 100 tonnes of LOX/methane, could return to orbit and leave 5 tonnes of propellant there for orbital or TEI uses, then return to the surface with another 20 tonnes of cargo.

The report also calls for a "base-first" strategy rather than a "super-sortie" approach. The latter sends a crew out who land, explore, and leave, like Apollo but for a much longer time. The former starts with lots of cargo landings, then humans follow. For the "base first" approach, a reusable lander is an important element.

SpaceNut · 2016-10-26 21:09:34

The capsule is using the side of the shape as a lifting body to slow the vehicle on entry which means the thermal protection is on the side. The length and width of the capsule means that we are having a heatshield that is larger than just an end only heat shield. This allows for a larger cargo mass to get to the surface.

The plan needs to also care for the crews health for the duration of the mission and here is what we are learning from the ISS... http://www.cnn.com/2016/10/26/health/as … index.html

A six-month stay on the International Space Station can be a pain in the back for astronauts. While they may gain up to 2 inches in height temporarily, that effect is accompanied by a weakening of the muscles supporting the spine, according to a new study. In the first year after their mission, astronauts have a 4.3 times higher risk of a herniated disc.

So what can we do if we do not have artificial gravity...

Yoga in space?
Because nobody likes back pain and muscle loss, Chang suggested countermeasures that should be added to the already two- to three-hour workout astronauts have on the space station each day. Though their exercise machines focus on a range of issues including cardiovascular and skeletal health, the team believes that space travelers also need to include a core-strenghtening program focused on the spine.

louis · 2016-10-27 06:00:51

Isn't that sort of landing pretty much what the Space Shuttle used to do before levelling out?

Whilst this sort of project may be feasible, development is going to take a long time. The Red Dragon could be used now to establish a base on Mars. It can carry a one tonne payload to Mars. Let's send 20-30 over ten years. We may also need to separately land an inflatable Bigelow style home hab and a Mars Rover. However, the Mars Rover might be sent in separate parts to be assembled on Mars. If we started now, with Space X's plans for the Red Dragon to fly to Mars orbit in 2018 we could be there by 2028 with a permanent base. The Red Dragon could be adapted to be an ascent craft as well.

RobS wrote:

Here's a plan for a reusable Mars lander: http://www.thespacereview.com/article/3085/1
Like the ITS, it would enter the Martian atmosphere at a 50 degree angle and would land vertically. It would mass 20 tonnes empty, could land 20 tonnes of cargo, could be refueled with 100 tonnes of LOX/methane, could return to orbit and leave 5 tonnes of propellant there for orbital or TEI uses, then return to the surface with another 20 tonnes of cargo.
The report also calls for a "base-first" strategy rather than a "super-sortie" approach. The latter sends a crew out who land, explore, and leave, like Apollo but for a much longer time. The former starts with lots of cargo landings, then humans follow. For the "base first" approach, a reusable lander is an important element.

kbd512 · 2016-10-27 10:17:53

louis wrote:

Isn't that sort of landing pretty much what the Space Shuttle used to do before levelling out?
Whilst this sort of project may be feasible, development is going to take a long time. The Red Dragon could be used now to establish a base on Mars. It can carry a one tonne payload to Mars. Let's send 20-30 over ten years. We may also need to separately land an inflatable Bigelow style home hab and a Mars Rover. However, the Mars Rover might be sent in separate parts to be assembled on Mars. If we started now, with Space X's plans for the Red Dragon to fly to Mars orbit in 2018 we could be there by 2028 with a permanent base. The Red Dragon could be adapted to be an ascent craft as well.

Louis,

The Space Shuttle lands on runways nearly three miles long. Max landing weight was approximately 90t. I thought it was 120t, but I was wrong. ITS will weigh about as much as a fully loaded AN-225 when it lands on Mars, although on Mars it would only weigh 228t with completely empty propellant tanks.

What happens if we put that much weight on sand? Will ITS just sink into the sand? Since ITS only has three landing legs, what happens if one of the landing legs lands on a rock and the other two legs land on sand? If ITS has already contacted the Martian surface successfully, but subsequently sinks into the sand after it lands, will it tip over if the ground isn't very flat or the regolith is less compacted under one leg than another? Does any of that seem a bit more dangerous than necessary?

Maybe the ITS landing gear needs guns loaded with stakes to anchor the craft to the ground on Mars.

I think Mr. Musk's ITS engineering team has their work cut out for them.

RobertDyck · 2016-10-27 12:48:10

kbd512 wrote:

Max landing weight was approximately 90t. I thought it was 120t, but I was wrong.

A couple web pages that NASA still has up...
Shuttle reference manual
Space Shuttle Basics
The "Basics" page has a yellow strip along the left side titled "Shuttle Statistics". That says Shuttle weight at end of mission was 104,326 kilograms (230,000 pounds). That's 104.326 metric tonnes.

Wikipedia: Space Shuttle
Specifications claim maximum landing weight was 100,000 kg, and Payload to Landing (Return Payload) 14,400 kg. However, I trust NASA's website more than Wikipedia.

kbd512 · 2016-10-27 14:50:29

RobertDyck wrote:

kbd512 wrote:
Max landing weight was approximately 90t. I thought it was 120t, but I was wrong.
A couple web pages that NASA still has up...
Shuttle reference manual
Space Shuttle Basics
The "Basics" page has a yellow strip along the left side titled "Shuttle Statistics". That says Shuttle weight at end of mission was 104,326 kilograms (230,000 pounds). That's 104.326 metric tonnes.
Wikipedia: Space Shuttle
Specifications claim maximum landing weight was 100,000 kg, and Payload to Landing (Return Payload) 14,400 kg. However, I trust NASA's website more than Wikipedia.

Rob,

No two Space Shuttles were exactly alike, but I believe the figure I quoted was for Columbia. The 14t increased MLW for Atlantis and Endeavor doesn't change the substance of the point I was trying to make. Mr. Musk wants to land something with a MLW that's more than double the MLW of any orbiter, on Mars, in the sand. There are no landing pads there. I would think it would be fairly obvious why we use runways or landing pads and launch pads here on Earth.

Maybe he has that all figured out. However, making the assumption that he does would be a mistake. The Spaceship has an estimated cost of $200M, but will probably be closer to $400M by the time the government finishes testing and tweaking it to perfection. I say that because Mr. Musk doesn't have the money to pay for it. That means NASA would have to pay for it, which is another way of saying that the taxpayers have to pay for it.

Uncle Sam will not allow someone to land a half billion dollar piece of aerospace hardware that he paid for on the surface of another planet without having a pretty high degree of certainty that it won't tip over and explode. You as well as anyone else here know how costly government bureaucracy can be, even when it doesn't need to be so costly. I'm pretty sure GW can also attest to that fact. Since we haven't set foot on the planet yet, there's no imperative to land 450t of cargo there.

I have an unpopular prediction to make. Nobody is going to ride in ITS. It'll be an autonomous system for delivering heavy cargo to LEO that's bound for Mars. All it will deliver is inflatable habitats with advanced propulsion systems or cargo with electric propulsion to LEO.

100 people that weigh 200 pounds each is only 20,000 pounds. The colonists will be packed like sardines into something that Falcon Heavy can deliver to orbit. If all aspects of the staged / pre-deployed hardware are in order, they'll ascend to orbit, dock with an oversized inflatable habitat that stays in space, and make the trip to Mars in a purpose-built habitat designed for in-space travel only. There's no need for them to wait for their ship to be fueled for a trip to Mars. You have to feed them when they're in space. Feeding 100 people circling the Earth for a month or two is an unnecessary expense that won't help improve their health or sanity, either.

If there's a problem with the rocket delivering the sardine can to orbit, then there's at least a chance of aborting and parachuting back to Earth. ITS has no such capability and it probably never will. Like GW said, it's a massive container ship. All container ships have relatively small crews.

Once the colonists arrive in Mars orbit, they'll board a reusable propulsively landed capsule that has the capability to abort to orbit, if necessary, for the trip to the surface. Any cargo required would've been pre-deployed and ready for use before they ever left Earth. Chemical rockets are so extraordinarily expensive to operate that the only reason to use them is the lack of a better propulsion system.

That's the only way I see Mr. Musk's plan working in his favor. That 1900t propellant requirement to reuse the spaceship after it lands on Mars, simply landing 230t on Mars, and multiple refueling events on both ends don't work in his favor, with respect to the economics of doing this.

louis · 2016-10-27 18:58:26

One thing I would say is it's a brave person who second guesses Elon Musk. I expect he's already worked out how to ensure a safe landing area for the ITS - will probably involve pre-scoping by a Red Dragon crew or similar.

kbd512 wrote:

louis wrote:
Isn't that sort of landing pretty much what the Space Shuttle used to do before levelling out?
Whilst this sort of project may be feasible, development is going to take a long time. The Red Dragon could be used now to establish a base on Mars. It can carry a one tonne payload to Mars. Let's send 20-30 over ten years. We may also need to separately land an inflatable Bigelow style home hab and a Mars Rover. However, the Mars Rover might be sent in separate parts to be assembled on Mars. If we started now, with Space X's plans for the Red Dragon to fly to Mars orbit in 2018 we could be there by 2028 with a permanent base. The Red Dragon could be adapted to be an ascent craft as well.
Louis,
The Space Shuttle lands on runways nearly three miles long. Max landing weight was approximately 90t. I thought it was 120t, but I was wrong. ITS will weigh about as much as a fully loaded AN-225 when it lands on Mars, although on Mars it would only weigh 228t with completely empty propellant tanks.
What happens if we put that much weight on sand? Will ITS just sink into the sand? Since ITS only has three landing legs, what happens if one of the landing legs lands on a rock and the other two legs land on sand? If ITS has already contacted the Martian surface successfully, but subsequently sinks into the sand after it lands, will it tip over if the ground isn't very flat or the regolith is less compacted under one leg than another? Does any of that seem a bit more dangerous than necessary?
Maybe the ITS landing gear needs guns loaded with stakes to anchor the craft to the ground on Mars.
I think Mr. Musk's ITS engineering team has their work cut out for them.

RobS · 2016-10-27 19:14:58

The Martian surface is packed gravel, basically, and in many places it is bedrock. Dunes shouldn't be hard to avoid. The engineers can look at the depth the one-tonne Viking landers' landing legs sank into the regolith to estimate its strength. After the first one lands safely, I suspect landing pads will be cleared and tested, also.

GW Johnson · 2016-10-27 19:38:04

I ran a soil bearing calculation over in the Mars Colonist thread. I used overconservative bearing criteria, and way too much weight. Looks like the pads needed are about the size illustrated in Musk's presentation. I think the Spacex guys must already have looked at this.

GW

kbd512 · 2016-10-27 22:47:46

louis wrote:

One thing I would say is it's a brave person who second guesses Elon Musk. I expect he's already worked out how to ensure a safe landing area for the ITS - will probably involve pre-scoping by a Red Dragon crew or similar.

I'm not second guessing Mr. Musk, Louis. I'm thinking about exactly what his ITS design proves he's thinking about. Structural mass is the enemy. ITS is 150t of dead weight that has to be orbited from the surface of the Earth, fueled with five additional flights of ITS tankers, TMI'd, captured, landed, refueled again, orbited again, TEI'd, captured again, and landed again. There's a reason that's never been done before. It's exceptionally time consuming, complicated, and most importantly for paying passengers... expensive.

Name a piece of 450t equipment that needs to be landed on Mars to start a colony. Mr. Musk's plan requires immediate advanced technological civilization tasks like utility grade power production, utility grade propellant production, and utility grade ice mining. The 1t payload of Red Dragon is too small for human exploration and the 450t payload is far more than required for human exploration. We need at least one human exploration mission to characterize the qualities and quantity of water in an area like the Hellas Basin and we also need to determine the exact composition of the landing area for ITS. I think a failure to do that would be an invitation to catastrophe.

The propellant tanks of the rocket are the most realistic storage facility for 1900t worth of propellants. Since we already know quite a bit about LOX, let's take a look at what NASA came up with for storage and transfer of densified LCH4 for Altair:

A Densified Liquid Methane Delivery System for the Altair Ascent Stage

Here's what we need to know to solution this problem since we're intent on storing such substantial quantities of LOX / LCH4 propellants on Mars instead of using smaller landers and more efficient in-space propulsion:

* tank surface area of the LOX and LCH4 tanks

* specific propellant tank composite material and thickness

* specific propellant tank insulation material and thickness

* Surface temperatures in the landing area

* cryocooler heat rejection requirements for operation in space and on the surface of Mars

* cryocooler power requirements

Phoenix Mars Lander Mission: Thermal and CFD Modeling of the Meteorological Instrument based on Flight Data

CO2 Insulation for Thermal Control of the Mars Science Laboratory

Orbital hard cryogen storage testbed proposal (LH2, not LCH4, but it's something):

CRYOTE (Cryogenic Orbital Testbed) Concept

Ground truth from the Opportunity Rover for Mars thermal inertia data

Here's a tool for us to use to characterize the Martian thermal environment:

MARSTHERM

More thermal environment characterization tools:

Mars Odyssey Mission THEMIS

kbd512 · 2016-10-27 23:06:55

GW Johnson wrote:

I ran a soil bearing calculation over in the Mars Colonist thread. I used overconservative bearing criteria, and way too much weight. Looks like the pads needed are about the size illustrated in Musk's presentation. I think the Spacex guys must already have looked at this.
GW

GW,

How level does the landing area have to be?

If the lander lands on ground solid enough to support the weight of the ship and one of the pads sets down on an iron meteorite or rock, what are the colonist's prospects for an upright and non-explosive finale to EDL?

Is there any feasible way for ITS to slowly rotate a little bit just after touchdown to clear obstructions from underneath the pads, sort of like taking your foot and clearing a patch of dirt, or would that likely cause the tipping event that we need to avoid?

GW Johnson · 2016-10-28 08:44:19

The right answer to your "how level?" question is I don't know. What I do know says the line of action of the weight vector has to fall within the polygon outlined by the centers of the landing pads. As you tip at increasing angles, that line of action can approach the boundary. Once it falls outside, you tip over.

That's an easier-to-incur problem with a triangle polygon that with a quadrilateral or higher, which is why 3-wheel cars have always deservedly been thought unstable. However, cars have lateral acceleration forces that these vertical landing rockets just don't have. Those lateral accelerations times car mass are horizontal vector components that "tip" the effective weight vector.

The height in 3-D to the cg influences this as well, since on a longer baseline, it only takes a smaller tipping angle to have the line of action hit the polygon boundary. My sense of the criteria derives from the Apollo LM designs, which is nose-to-tail dimension roughly equal to pad-to-pad dimension, done with 4 legs. That'll handle some pretty rough ground, but as Apollo 11 showed, not boulders of a dimension exceeding ~5-10% of the lander dimension.

There's some stroke to the legs, even on Musk's ITS, according to his animations. That'll handle some uneveness, but is limited in response time. That's a worry if one pad hits a boulder: it'll likely suddenly crack and crush, causing a sudden gear leg extension transient that the shock absorbers cannot handle. So, we're looking for rocks-or-not on potential landing sites, at the scale of a meter or so.

My guess is that's one of the objectives of a Red Dragon pathfinder mission to a potential site. Looking for how big and how widely distributed the rocks really are. That stuff under a meter size doesn't seem to be within the resolution of photography from orbit. It could be, we have spy satellites better than that, but that's not what we sent to Mars.

The answer to your "push the rocks out of the way?" question is also "I don't know, but....". In this case the "but" is knowing ahead of time the site is clean down to an acceptable scale. It sure would be a complication to the hovering flight control. Really small stuff is likely to be blown out of the way by the jet blast. But blowing dust and sand away potentially uncovers buried boulders (although we didn't really see that on the moon). So, I just don't know.

Myself, I'd rather land a thing that large on a graded-and-paved pad. But the same risks apply to smaller landers, and at smaller boulder sizes. It's rock:lander proportion of dimensions that governs risks, I'd think. So all the concepts suffer from this risk, including all the habs and equipment to be landed in things like Mars Direct.

GW

Last edited by GW Johnson (2016-10-28 08:48:52)

RobS · 2016-10-28 09:07:24

If they land something robotic and smaller first, they have two options: (1) clear an area with some sort of small rover; (2) use a radio beacon to guide the landing. It is quite clear from the Falcon 9 first stage landings that Space x can put something down very precisely. The first few landings on Mars will help them refine that ability. If Space X launches a small satellite swarm into Mars orbit (remember they are planning to launch a big one into Earth orbit) then GPS may be available to refine the landing as well.

As for surface resolution, GW, you are right that a meter or a bit less is the best they currently have. But there's a new software routine available now that allows them to take multiple photos of an area--I think at the same time or under the same lighting conditions--and combine them to improve the resolution. I think I read they think they may be able to achieve 10 centimeters resolution eventually. I don't remember where I read this, but it was back when they found the Beagle lander six months or so ago, so maybe someone can come across it again. That would be quite a breakthrough.

If I may reminisce a moment, I was a 22-year old graduate student at Jet Propulsion Laboratory working on the Viking mission in the summer of 1976. The images coming back from the orbiter suggested that certain areas were smooth; but of course their best resolution was some tens of meters, I think, so that wasn't very precise. Meanwhile, radar data coming back from Arecibo suggested that those "smooth" areas had a high surface roughness--lots of rocks--and other areas that the orbital imagery suggested were fairly rough were actually smooth! This was a huge dilemma. The Viking team had a series of potential landing ellipses, but Mariner 9 orbital data wasn't very good, so they had planned to wait until Viking went into orbit to finalize the landing site. The conflicting data postponed the landing from July 4, 1976, to July 20. They finally settled on a compromise landing site that was not too rough according to either set of data. But if Viking 1 had come down just a few meters away, it would have hit "Big Joe" and tipped over. I don't remember how big "Big Joe" was; I think about three feet high and wide. And Viking 1 had no ability to steer itself.

louis · 2016-10-28 18:08:18

Surely with advanced computer technology we could land a (smallish - 1 tonne, say) bulldozer rover that can itself clear an area of rocks and/or determine if some boulders are too large to be cleared. It could then automatically clear a landing area...and having done so, it might then "paint" (or deposit small stones) to mark the landing zone...so landing craft can zero in on it (a visual marker to add to radio beacons).

louis · 2016-10-28 18:15:44

kbd, I'm not really a fan of Musk's "big is beautiful" approach. I was simply thinking he will have addressed the landing area issue for such a big craft.

Personally I think we could do Mars exploration based on a Red Dragon plus approach (the plus being pre-landing some bigger loads e.g. the home habitat). I don't think the 1 tonne is too small for that purpose.

My view is that Mars is a cornucopia of resources and that the key to successful colonisation is (a) utilisation of those resources and (b) gradual build-up of the colony on the basis of ISRU (rather than Musk's "Big Bang" approach).

Of course if Musk can prove me wrong I will be more than happy!

kbd512 wrote:

louis wrote:
One thing I would say is it's a brave person who second guesses Elon Musk. I expect he's already worked out how to ensure a safe landing area for the ITS - will probably involve pre-scoping by a Red Dragon crew or similar.
I'm not second guessing Mr. Musk, Louis. I'm thinking about exactly what his ITS design proves he's thinking about. Structural mass is the enemy. ITS is 150t of dead weight that has to be orbited from the surface of the Earth, fueled with five additional flights of ITS tankers, TMI'd, captured, landed, refueled again, orbited again, TEI'd, captured again, and landed again. There's a reason that's never been done before. It's exceptionally time consuming, complicated, and most importantly for paying passengers... expensive.
Name a piece of 450t equipment that needs to be landed on Mars to start a colony. Mr. Musk's plan requires immediate advanced technological civilization tasks like utility grade power production, utility grade propellant production, and utility grade ice mining. The 1t payload of Red Dragon is too small for human exploration and the 450t payload is far more than required for human exploration. We need at least one human exploration mission to characterize the qualities and quantity of water in an area like the Hellas Basin and we also need to determine the exact composition of the landing area for ITS. I think a failure to do that would be an invitation to catastrophe.
The propellant tanks of the rocket are the most realistic storage facility for 1900t worth of propellants. Since we already know quite a bit about LOX, let's take a look at what NASA came up with for storage and transfer of densified LCH4 for Altair:
A Densified Liquid Methane Delivery System for the Altair Ascent Stage
Here's what we need to know to solution this problem since we're intent on storing such substantial quantities of LOX / LCH4 propellants on Mars instead of using smaller landers and more efficient in-space propulsion:
* tank surface area of the LOX and LCH4 tanks
* specific propellant tank composite material and thickness
* specific propellant tank insulation material and thickness
* Surface temperatures in the landing area
* cryocooler heat rejection requirements for operation in space and on the surface of Mars
* cryocooler power requirements
Phoenix Mars Lander Mission: Thermal and CFD Modeling of the Meteorological Instrument based on Flight Data
CO2 Insulation for Thermal Control of the Mars Science Laboratory
Orbital hard cryogen storage testbed proposal (LH2, not LCH4, but it's something):
CRYOTE (Cryogenic Orbital Testbed) Concept
Ground truth from the Opportunity Rover for Mars thermal inertia data
Here's a tool for us to use to characterize the Martian thermal environment:
MARSTHERM
More thermal environment characterization tools:
Mars Odyssey Mission THEMIS

kbd512 · 2016-10-29 11:49:13

louis wrote:

kbd, I'm not really a fan of Musk's "big is beautiful" approach. I was simply thinking he will have addressed the landing area issue for such a big craft.
Personally I think we could do Mars exploration based on a Red Dragon plus approach (the plus being pre-landing some bigger loads e.g. the home habitat). I don't think the 1 tonne is too small for that purpose.
My view is that Mars is a cornucopia of resources and that the key to successful colonisation is (a) utilisation of those resources and (b) gradual build-up of the colony on the basis of ISRU (rather than Musk's "Big Bang" approach).
Of course if Musk can prove me wrong I will be more than happy!

Unfortunately, Mr. Musk is just a launch services provider. He's highly intelligent, highly successful and resourceful, and people listen when he speaks, but he can't conjure up technologies that don't exist with his limited budget.

It's a wonderful dream and I much prefer his vision of the future to the reality created by our politicians, but the mechanics of successfully transporting 100 people to Mars just once, let alone 10,000 times, is an unyielding obstacle. The economics of that task will force us to use more efficient propulsion systems. I seriously doubt that manufacturing 1,900t of propellants on Mars is simpler or easier to accomplish than developing a more efficient in-space propulsion method.

Red Dragon is another tool in our tool box for robotic exploration, but human exploration requires much greater delivered tonnage. Thus far, we've avoided the problem of delivering more tonnage to the surface of Mars. It's long past time to develop landers capable of delivering multiple tons of payload.

NASA hasn't tested a propellant plant demonstrator on Mars, either. After a technology has been successfully demonstrated, someone has to scale up that technology to reliably provide 1900t worth of propellant from ice and CO2. There has been very little development of this technology.

Tom Kalbfus · 2016-10-29 12:05:25

kbd512 wrote:

louis wrote:
Isn't that sort of landing pretty much what the Space Shuttle used to do before levelling out?
Whilst this sort of project may be feasible, development is going to take a long time. The Red Dragon could be used now to establish a base on Mars. It can carry a one tonne payload to Mars. Let's send 20-30 over ten years. We may also need to separately land an inflatable Bigelow style home hab and a Mars Rover. However, the Mars Rover might be sent in separate parts to be assembled on Mars. If we started now, with Space X's plans for the Red Dragon to fly to Mars orbit in 2018 we could be there by 2028 with a permanent base. The Red Dragon could be adapted to be an ascent craft as well.
Louis,
The Space Shuttle lands on runways nearly three miles long. Max landing weight was approximately 90t. I thought it was 120t, but I was wrong. ITS will weigh about as much as a fully loaded AN-225 when it lands on Mars, although on Mars it would only weigh 228t with completely empty propellant tanks.
What happens if we put that much weight on sand? Will ITS just sink into the sand? Since ITS only has three landing legs, what happens if one of the landing legs lands on a rock and the other two legs land on sand? If ITS has already contacted the Martian surface successfully, but subsequently sinks into the sand after it lands, will it tip over if the ground isn't very flat or the regolith is less compacted under one leg than another? Does any of that seem a bit more dangerous than necessary?
Maybe the ITS landing gear needs guns loaded with stakes to anchor the craft to the ground on Mars.
I think Mr. Musk's ITS engineering team has their work cut out for them.

Mars isn't all sand dunes, it has bedrock too.

GW Johnson · 2016-10-29 16:01:15

"Red Dragon is another tool in our tool box for robotic exploration, but human exploration requires much greater delivered tonnage. Thus far, we've avoided the problem of delivering more tonnage to the surface of Mars. It's long past time to develop landers capable of delivering multiple tons of payload."

If retro-propulsive Red Dragon works, then things of any mass will work. It's chutes that are mass-loading and Mach number limited. It's just a matter of scale and Isp to find out how much cargo can be landed retro-propulsively.

My lander for the 1950's mission update is around 60-65 tons at ignition, and delivers just over 3 tons to the surface of Mars, while still able to fly back to Mars orbit, completely unrefuelled. It is a MMH-NTO system.

Don't be fooled by all the hype about 100-people-to-Mars and million-population colonies. That's not what Musk is up to! He's merely creating a transportation system that can serve from the first missions to the establishment of said colony. Which is way far more than ANYBODY else can claim.

The first missions may well be unmanned. The first several missions will be very small crews and around a hundred tons of cargo, equipment, and supplies. Think 4-6 people in crews that rotate home every mission the first several years.

Can no one else tell reality from fantasy here?

GW

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