Author Topic: A Mars Launchpad for MCT  (Read 43996 times)

Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #40 on: 05/19/2015 04:00 PM »
shill does it again.

A leap forward to resolving a conundrum, setting up the problem, and offering a detailed solution. I guess we can fold up the tent and continue the caravan to the next topic!  :D

(However, I may have a few questions about details.)
« Last Edit: 05/19/2015 05:11 PM by Ionmars »
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Offline guckyfan

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Re: A Mars Launchpad for MCT
« Reply #41 on: 05/19/2015 04:37 PM »

1) You suggested that the first MCTs will not return to Earth, but will deliver large loads of supplies and equipment for exploration and colonization. Makes logical sense, but it seems to contradict the principal of reusability. Perhaps they will return to Earth when a better launch pad has been developed on Mars?

I always assumed that the first one or two MCT might not return. They will be needed for a while on Mars. There is also lacking infrastructure to launch them. They might be able to launch 2 or 4 years later but I am not sure I would trust them after that time exposed to martian conditions and without proper maintenance. Better use their tanks and cargo holds on Mars. I don't see that as a violation of the reuse principle.

2) Non-returning MCTs really don't address the main problem, i.e. that the exhaust plumes will kick up debris that will likely damage the engines. If we accept that this will occur, would it not make more sense that the first supply trips will utilize smaller vehicles with canted engines that avoid this problem? (Not as tidy a solution because the amount of cargo delivered on each trip would be less.)

Smaller vehicles need to be developed and tested first too. IMO much cheaper to use full size from the beginning. Maybe not load them with 100% capacity. Give room for error. If the engine bells get damaged 1m above ground it would not jeopardize the landing, only relaunch. I also always assumed that a Red Dragon or two would be used to survey and select the landing site and maybe remove some boulders. But that would not be full up preparation of the landing site.

Offline D_Dom

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Re: A Mars Launchpad for MCT
« Reply #42 on: 05/19/2015 04:41 PM »
I have a problem accepting that exhaust plumes will kick up debris that will damage the engines without better understanding the variables involved.

 One is the weight of the vehicle, non-returning MCTs could address that by design.

 Another is material strength of landing zone itself, from the 2009 NASA report cited upthread;
"This has been demonstrated in large-scale engine tests in sand and clay (Alexander, et al, 1966) 25, small-scale experiments (Metzger, 2007) 26, numerical simulations (Liever, et al, 2007) 27, and soil dynamics analysis (see section 5.10.2.3), so there is no question that this will occur. It did not occur in the Apollo and Viking missions because the thrust was lower and/or because the lunar regolith had higher shear strength and less permeability than martian soil."
I propose that we will have a much better understanding of martian soil providing an ability to select appropriate landing zones.
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #43 on: 05/19/2015 04:45 PM »
...
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I always assumed that the first one or two MCT might not return. They will be needed for a while on Mars. There is also lacking infrastructure to launch them. They might be able to launch 2 or 4 years later but I am not sure I would trust them after that time exposed to martian conditions and without proper maintenance. Better use their tanks and cargo holds on Mars. I don't see that as a violation of the reuse principle.
...
...
Smaller vehicles need to be developed and tested first too. IMO much cheaper to use full size from the beginning. Maybe not load them with 100% capacity. Give room for error. If the engine bells get damaged 1m above ground it would not jeopardize the landing, only relaunch. I also always assumed that a Red Dragon or two would be used to survey and select the landing site and maybe remove some boulders. But that would not be full up preparation of the landing site.
I think you on the right track. Makes sense.
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #44 on: 05/19/2015 04:52 PM »
I have a problem accepting that exhaust plumes will kick up debris that will damage the engines without better understanding the variables involved.

 One is the weight of the vehicle, non-returning MCTs could address that by design.

 Another is material strength of landing zone itself, from the 2009 NASA report cited upthread;
"This has been demonstrated in large-scale engine tests in sand and clay (Alexander, et al, 1966) 25, small-scale experiments (Metzger, 2007) 26, numerical simulations (Liever, et al, 2007) 27, and soil dynamics analysis (see section 5.10.2.3), so there is no question that this will occur. It did not occur in the Apollo and Viking missions because the thrust was lower and/or because the lunar regolith had higher shear strength and less permeability than martian soil."
I propose that we will have a much better understanding of martian soil providing an ability to select appropriate landing zones.
I course you are right that we need more data on Mars' soils before committing to a landing site. For this thread I would propose the conservative approach, that we accept these findings until the better data proves otherwise.
« Last Edit: 05/19/2015 05:10 PM by Ionmars »
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Offline sghill

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Re: A Mars Launchpad for MCT
« Reply #45 on: 05/19/2015 07:00 PM »
Three additional thoughts that I didn't add to my previous post because I didn't want to distract.

1) The problem goes away with nice long landing gear struts. :)
2) The problem goes away if you land on a hard lava field. (terrain smoothness may be an issue though).
3) My proposed non-returning MCT's may only be there to support the initial manned landings, and then eventually they will return- or even have the capability to function as lifeboats.  I think not though.  All of the hints we've had about SpaceX's Mars exploration architecture indicates that some of the things astronauts will need to return home will already be waiting for them.  That means some initial launches of unmanned "factory" or "utility" MCTs.  Plus they can be stuffed full of spare parts (plus they can scavenge the crafts' other components for more spares). 

Several early unmanned colony preparation/factory ships will add huge safety margins to the first manned flights to and from any planetary body by creating redundancy of critical systems and reducing the need to carry lots of supplies on crewed missions.  So much so, that I think it's the critical path.


1) You suggested that the first MCTs will not return to Earth, but will deliver large loads of supplies and equipment for exploration and colonization. Makes logical sense, but it seems to contradict the principal of reusability. Perhaps they will return to Earth when a better launch pad has been developed on Mars?

I always assumed that the first one or two MCT might not return. They will be needed for a while on Mars. There is also lacking infrastructure to launch them. They might be able to launch 2 or 4 years later but I am not sure I would trust them after that time exposed to martian conditions and without proper maintenance. Better use their tanks and cargo holds on Mars. I don't see that as a violation of the reuse principle.

YES! THIS!!!
« Last Edit: 05/19/2015 08:04 PM by sghill »
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #46 on: 05/20/2015 07:55 PM »
sghill, you have already given us the solution. We will prepare the ground for MCT using those robotic vehicles and equipment. Just use Dragon 2 or similar vehicle to land the equipment.
« Last Edit: 05/21/2015 09:49 PM by Ionmars »
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Offline Paul451

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Re: A Mars Launchpad for MCT
« Reply #47 on: 05/26/2015 06:35 PM »
Random thought: If you're sending a few non-returning MCTs, could they be landing pads for the later relaunchables?

Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #48 on: 06/01/2015 11:46 AM »
Random thought: If you're sending a few non-returning MCTs, could they be landing pads for the later relaunchables?
Do you mean bringing to Mars the materials and equipment for a launch pad? Interesting. Could you spell out your idea a little further?
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Online spacenut

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Re: A Mars Launchpad for MCT
« Reply #49 on: 06/01/2015 01:46 PM »
I've mentioned this before, do like they did in WWII in the Pacific.  Have a small grader land and smooth out a spot.  Then with the first lander, have lightweight steel plate that can be locked together and spread out over the graded area.  They did this for runways on islands in the Pacific during WWII.  They didn't have time to mix and wait for concrete to harden.  The mats were lightweight by use of a lot of holes in the steel.  This should work fine, or some lightweight aluminum panels, but steel has a higher melting point.  If they can land on a small barge, they can land on say a 50m x 50m pad, or pads. 

Another simple solution is to have the engines mounted on the sides in pods, like the Dragon 2, but with vertical sides.  They would be high enough to stir up mostly dust.  I think debris is overblown for damage though.  Pick the right landing areas. 

Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #50 on: 06/01/2015 02:33 PM »
I've mentioned this before, do like they did in WWII in the Pacific.  Have a small grader land and smooth out a spot.  Then with the first lander, have lightweight steel plate that can be locked together and spread out over the graded area.  They did this for runways on islands in the Pacific during WWII.  They didn't have time to mix and wait for concrete to harden.  The mats were lightweight by use of a lot of holes in the steel.  This should work fine, or some lightweight aluminum panels, but steel has a higher melting point.  If they can land on a small barge, they can land on say a 50m x 50m pad, or pads. 

Another simple solution is to have the engines mounted on the sides in pods, like the Dragon 2, but with vertical sides.  They would be high enough to stir up mostly dust.  I think debris is overblown for damage though.  Pick the right landing areas.
Yeah I agree that something like the WWII landing pads could work.

I think the canted engines on a Dragon 2 will be necessary for landing on a unprepared site. The NASA studies cited earlier said that any large (>30 t) vehicle with engines underneath would definitely have debris blasted vertically into the engine compartment. (I took that to mean the spaces between engines.) Apparently a plume directed downward reflects back up when hitting a surface and burning a crater into that surface. The canted engines on D2 avoids this by directing the flames outward.

So I'm thinking D2 to employ the landing  pad that the larger MCT can land on later.
« Last Edit: 06/01/2015 02:39 PM by Ionmars »
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Offline sghill

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Re: A Mars Launchpad for MCT
« Reply #51 on: 06/01/2015 02:53 PM »
So I'm thinking D2 to employ the landing  pad that the larger MCT can land on later.

I'm giving this one the thumbs down even though I don't want to. :)

For the sake of the thought experiment, I'll give benefit of the doubt and say that some sort of sheeting can be used to cover the ground in order to make a pad.  Let's further assume that this material is light enough and thin enough to roll up into a D2 (never mind how we'll get it out and deployed) for shipment to Mars while also being strong enough to withstand the blast from multiple Raptor engines.

1) The rocks still need to get smoothed out before the sheeting can be unfurled.  An earth mover is still required for a pad.
2) There has to be some device or methods to unfurl the sheeting that also fit within the D2.  Even if an inflatable ring pulls the edges tight, it just doesn't pass the giggle test of feasibility.
3) The sheeting has to be anchored to the ground at multiple points to avoid being blown away when the engines start or when an MCT lands.  Think of what happened to those flags on the Moon when the landers lifted off.
4) The MCT has to make a pin point landing (as in zero inches off of its intended target spot) directly on top of a pad that was small enough to be stowed and then deployed within a D2.  If it misses, the pad is useless.

And this all assumes that a material that can handle the first assumptions can be found.  Let's all yell "graphene solves everything" and call it a day... :)

As soon as you get to point #1 above, you might as well use the vitrification method because it's simpler.
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #52 on: 06/01/2015 03:13 PM »
Earlier in this thread we discussed how to exploit a small crater as a landing and launch (L/L) site.  I've drawn a crude sketch below to show how this could work. The sketch incorporates these principles:

(1) The crater is small, only 0.5 to 2 km diameter. Its purpose is to contain flying FOD during L/L activity.

(2) The bottom of the crater is employed for L/L.

(3) The crater rim is used to shield fuel tanks and equipment from flying FOD during L/L.

(4) The equipment area and landing site are located as close together as feasible within the limits of safety. In the example this is 150 m. The purpose is to limit the length of pipeline required to bring fuel from the tanks behind the rim to fuel-loadung equipment at the L/L site.

(5) If dirt-moving equipment is available, the tank area can be improved as shown in the sketch. Flatten the area behind the rim and use excavated material to build a small berm on top of the crater rim. Some of the material could be fill to widen the tank equipment area.

(6) The slope of the crater sidewall is modest (1:3) to allow mobile equipment to easily navigate between the L/L site and the crater rim.

The motivation of this arrangement is to exploit a natural feature that can reduce the amount of construction work required to set up an initial L/L site. Note that a man-made berm to protect equipment could be as high as this crater rim for the same purpose. (A big project with few resources.)

« Last Edit: 06/01/2015 03:15 PM by Ionmars »
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Offline KelvinZero

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Re: A Mars Launchpad for MCT
« Reply #53 on: 06/01/2015 03:22 PM »
Stumbled on this.. Didn't see it mentioned previously.
http://www.nasa.gov/content/landing-pads-being-designed-for-extraterrestrial-missions

It noted that you only need the very high quality material dead center, and the best material is the same as used on heat shields.

It also mentioned "basalt regolith mixed with polymer binders". You might be able to create polymer binders with just water and atmosphere ISRU.
« Last Edit: 06/01/2015 03:30 PM by KelvinZero »

Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #54 on: 06/01/2015 03:30 PM »
So I'm thinking D2 to employ the landing  pad that the larger MCT can land on later.
I'm giving this one the thumbs down even though I don't want to. :)
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...
As soon as you get to point #1 above, you might as well use the vitrification method because it's simpler.

OK, point well taken. Your low-mass vitrification method will be preferred over hauling a landing pad from Earth. You are hauling only the equipment and not the mass of the pad itself.
I believe you are referring to the technique you presented in Reply #39 on this thread.
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #55 on: 06/01/2015 03:41 PM »
Stumbled on this.. Didn't see it mentioned previously.
http://www.nasa.gov/content/landing-pads-being-designed-for-extraterrestrial-missions

It noted that you only need the very high quality material dead center, and the best material is the same as used on heat shields.

It also mentioned "basalt regolith mixed with polymer binders". You might be able to create polymer binders with just water and atmosphere ISRU.
Thank you for this reference. It provides additional verification for what we said earlier on this thread; to wit:

"Our best estimates indicate that descent engines of the Apollo landers were ejecting up to one-and-a-half tons of rocks and soil," said Dr. Phil Metzger, a research physicist in Kennedy's Granular Mechanics and Regolith Operations Laboratory. "It will be even more challenging when we land humans on Mars. The rocket exhaust will dig a deep hole under the lander and fluidize the soil. We don't know any way to make this safe without landing pads."
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #56 on: 06/01/2015 03:58 PM »
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OK, point well taken. Your low-mass vitrification method will be preferred over hauling a landing pad from Earth. You are hauling only the equipment and not the mass of the pad itself.
I believe you are referring to the technique you presented in Reply #39 on this thread.

To implement the vitrification method that you recommended, there is some engineering research to be carried out (if it has not been done already.
 
First we need to know more about the ground materials at the particular site to be vitrified. (duh)

Second, we need to know the depth of vitrified material that is necessary to prevent the exhaust plume of a landing MCT from melting through it.

Third, these two elements together will determine the size and depth of electrodes to be employed, and
 
Fourth, the megawatts of power required to drive the process.
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Offline Ionmars

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Re: A Mars Launchpad for MCT
« Reply #57 on: 06/01/2015 04:20 PM »
After posting the Reply #58 above, it occurred to me that ground material that has been melted/vitrified by electrodes could be melted again by the exhaust plume(s) of an MCT. After all, it is the same material even if it has been melted once. So I'm thinking that a crater would still form and debris still be propelled vertically.

So we may be back to importing some landing pad material that is better than Mars surface and better than common steel used in WWII landing pads. Maybe a sheet that fits over a vitrified area?

Does anyone know the material(s) used for the autonomous spaceport drone ship (ASDS)?
« Last Edit: 06/01/2015 04:21 PM by Ionmars »
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Offline Paul451

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Re: A Mars Launchpad for MCT
« Reply #58 on: 06/01/2015 06:59 PM »
Second, we need to know the depth of vitrified material that is necessary to prevent the exhaust plume of a landing MCT from melting through it.

Not just melt it, mechanically blast it into chunks. Hence depth alone may not be enough to prevent the surface layer from breaking up (although a lack of depth certainly won't help.)

The strength of the melted deck can be calculated once we know more about the composition of the first few feet of martian soil at the launch/landing site. IMHO, it doesn't matter though.  The only difference is how long the vitrification skid takes at each spot.  The longer has to linger, the deeper and stronger the glassified soil gets.

The article KelvinZero linked to suggests that basalt isn't strong enough. That excludes simple vitrified regolith.

but anything brought from Earth to Mars will cost billions of dollars.

If it does, then you ain't goin' to Mars.

Dead masses like aluminum plating simply won't be on a shipping manifest when there is plenty of dead mass (air, water, rocks, and minerals) are already on Mars. [...] Therefore, the critical path falls on equipment that utilizes available energy and time to prepare a pad with the dead mass already on Mars.

However, a landing pad is a single specialist item. Unlike fuel/air/water, it's not something a settlement is going to be making by the hundreds every year (well, maybe with "Musk's million"...), therefore the imported equipment used to manufacture an ISRU pad is likely to be pretty close to the mass of a pre-manufactured pad. Combined with the complexity, energy cost, time, parts, plant repair robots (no pad means no humans) of vitrification... importing a known quantity for such an important element may win out over any remaining mass benefits of ISRU.

That said, the simple solution may just be side-mounted angled-thrust engines on the MCT; a broad landing area (tanks empty, engines throttled down, low thrust/low blast impact), with a separate launch pad being a small area of compacted rock at the centre and crude blast trenches under each engine to direct its blast away. Simply site your other facilities out of the line of those blast trenches. Bring in one robo-crawler-jack-thing for each leg of the MCT, carry it from the broad landing pad to the refuelling station, then from the refuelling station to the smaller launch pad, carefully aligned with the flame diversion trenches, then scoot out of the way. In between launches they are the chassis for your heavy earthwork equipment.

Bam! Done. Thread over. Go home.
« Last Edit: 06/01/2015 10:18 PM by Paul451 »

Offline Paul451

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Re: A Mars Launchpad for MCT
« Reply #59 on: 06/01/2015 07:06 PM »
On the other hand...

Random thought: If you're sending a few non-returning MCTs, could they be landing pads for the later relaunchables?
Do you mean bringing to Mars the materials and equipment for a launch pad?

Nope. I mean the top of the expendable MCTs are the landing pad for relaunchable MCTs.

It's a very small target, but you control the surface, you are further above the ground, you can pre-install a flame-diverter, you can pre-install nice hard points to attach your crane(s), swingaway gantries and refuelling connectors, and it gives some protection for fuel lines running from the refuelling system (which is presumably yet another expendable MCT.)

It's not a particularly serious thought, just popped into my head reading three comments together quickly: one talking about laying out steel/aluminium plates on the ground, the second talking about the need to raise the engines away from ground-level, and the third assuming-out-loud that the first few MCTs will be non-returning... So... if you've got all that hardware just sitting there... and you need something to land on...

This is another time I wish I had any artistic ability to sketch something up. But basically this:


(wings? wheels? wtf? I know, but it's the closest I could find to what's escaped from the L2 render project.)

combined with this:


and this:



and this:

Quote
"the one substance for landing pads that shows the most promise is the material used on spacecraft heat shields."

...plus a lot of handwaving and cheek puffing...

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