Martian Spaceport

[lamontagne]

The SpaceX Martian colony will eventually need a spaceport.  This facility may begin, literally, as a hole in the ground, or it may need to be more sophisticated.  Elon Musk has already stated that the two first ships on Mars will not be returning.  However, plans are made to be changed, so even that may not be an absolute.

To design the Spaceport, we need to identify the requirements:
-Material handling
-Propellant storage and transfer
-Risks from malfunctioning spacecraft
-Local resources that can be used to build the spaceport

And to take into account the limitations of the site, including the colony and the adequate distance required for safety.

Can we simply go by the existing facilities on Earth, or are there special considerations for Mars?

Illustrated, for discussion's sake, is a possible early Spaceport.  The design has already been severely criticized for design problems, so it is merely a starting point for the discussion, not a final proposition!  In particular is was about 100m from the base, and generally this was criticized as being much too close.

The absence of a flame trench is also a possible fatal flaw.

The little white machine in the second image is a pad cleaner.  Rather like an ice hockey Zamboni.
The spaceships are moved around by self propelled transporters, like Hopper.

I've also included an image on an earlier design with a flame trench, but I felt it was too complex for the early stage of the colony, but I may have been wrong.

I've removed the colony for the moment because it make the model unwieldy.  Too many polygons.

[lamontagne]

And about local resources, does the existence of carbonates on Mars mean that we can expect to make a poured in place concrete pad, or is that still in question?  I'm going by the Wikipedia page: https://en.wikipedia.org/wiki/Carbonates_on_Mars

[Steve D]

Let me ask again here.

How would a starship blowing up on Mars actually work? On earth there is a large amount of oxygen in the atmosphere which enables all of the fuel to burn. On Mars its a near vacuum with no oxygen. How fast would a starship fully loaded with fuel and oxygen that breaches its tanks burn? How quickly would the fuel and oxygen disperse to where it wouldnt burn any more? If just one tank is breached there wouldnt be any fire or explosion.

How much space would be needed? Unlike on Earth just a fuel leak even if major would not turn into a fire or explosion. Same with just an oxygen leak. you would need both to leak and mix at a high enough partial pressure to allow for a fire.

So what would be a safe distance to the colony?

[lamontagne]

Some resources for the discussion:

Densified oxygen for X-33: https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100035154.pdf
Picture of SLC-40 and scale
Pictures of Vandenberg
Baikonour

[Lampyridae]

I was going to point it out in the Amazing Habitats thread, but the main issue for a colony spaceport (besides the direct main engine blast) is the dust being turned into a sandblast. Mars' low air pressure means the plume also extends pretty far. The MSL Skycrane plume started kicking up dust at 63m, excluding the cosine for the angled motors.
What prevented deeper excavation of the Skycrane craters seemed to be a layer of frost just below the surface.
Fortunately there's some atmosphere to stop the dust turning into a hypervelocity sandblaster.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150002954.pdf

Given that plume length is roughly proportional to nozzle diameter, the 63m dust-stirring height from 20cm Skycrane nozzles would scale up to 315 diameters,  ~500m for the Starship's Raptors, effectively blanketing the immediate vicinity in dust. So the spaceport design would have to account for that.

[Paul451]

Moved from the Envisioning Habs thread:

How would a starship blowing up on Mars actually work? [...] How fast would a starship fully loaded with fuel and oxygen that breaches its tanks burn? [...] If just one tank is breached there wouldnt be any fire or explosion.

DO YOU BLEVE. (Doesn't even need to be a flammable gas.)

And such a rupture of one tank will cause a structural failure of the vehicle, causing the second tank to break open, even if just from falling debris, causing a second BLEVE, which will cause the two propellants to mix in a nice way for a final kablooie.

And if you are preparing multiple SS's (crew and cargo) near the pad for the return trip, with enough fuel stored nearby for all of them, a single failure of either an SS or one of the storage tanks, you'll take out the whole fleet in additional to all the fuelling infrastructure. And the base itself if you are close enough. The cost of an accident is so great, while the cost of adding an extra mile or two of distance between launchpad and base so trivial by comparison, it's crazy to just cross your fingers and hope that nothing goes wrong.

You have to plan for a major failure on Mars. Just as you have to plan your supplies on Mars around a failure on Earth grounding the fleet for long enough to miss at least one full synod.

[Slarty1080]

And about local resources, does the existence of carbonates on Mars mean that we can expect to make a poured in place concrete pad, or is that still in question?  I'm going by the Wikipedia page: https://en.wikipedia.org/wiki/Carbonates_on_Mars

Perhaps, but there are a lot of different structural materials that might be used. Although we find it convenient to use traditional concrete on Earth, there may be other solutions more appropriate for Mars. Chemistry provides a range of possibilities. Sulphur can be used to make strong cement (no water required) or regolith could simply be compressed into bricks.

[Slarty1080]

I was going to point it out in the Amazing Habitats thread, but the main issue for a colony spaceport (besides the direct main engine blast) is the dust being turned into a sandblast. Mars' low air pressure means the plume also extends pretty far. The MSL Skycrane plume started kicking up dust at 63m, excluding the cosine for the angled motors.
What prevented deeper excavation of the Skycrane craters seemed to be a layer of frost just below the surface.
Fortunately there's some atmosphere to stop the dust turning into a hypervelocity sandblaster.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150002954.pdf

Given that plume length is roughly proportional to nozzle diameter, the 63m dust-stirring height from 20cm Skycrane nozzles would scale up to 315 diameters,  ~500m for the Starship's Raptors, effectively blanketing the immediate vicinity in dust. So the spaceport design would have to account for that.

Apart from the crash risk there is also the blown debris risk and the exhaust stream blast risk. Even on a prepared pad there will be dust and probably small amounts of erosion debris as well which will need to be mitigated. Things like vast solar arrays with their high surface area and low mass would be very vulnerable to blast and dust and would need to be sited well clear. A waft of wind and a little dust around the habitat is undesirable but it could be even more problematic for the solar array.

[lamontagne]

Putting out a few numbers:
Cost of Mars propellant per ship
Cost of a 5km road sized to transport a Starship
Cost of a 100m diameter pad.

[lamontagne]

And about local resources, does the existence of carbonates on Mars mean that we can expect to make a poured in place concrete pad, or is that still in question?  I'm going by the Wikipedia page: https://en.wikipedia.org/wiki/Carbonates_on_Mars

Perhaps, but there are a lot of different structural materials that might be used. Although we find it convenient to use traditional concrete on Earth, there may be other solutions more appropriate for Mars. Chemistry provides a range of possibilities. Sulphur can be used to make strong cement (no water required) or regolith could simply be compressed into bricks.

I was wondering that since there seems to be large amounts of water on Mars, and that the colony will need a lot of water anyway to operate a propellant plant and it's overall operations, is sulfur concrete still interesting?
Although I love the idea of compressed regolith bricks and blocks, I do wonder about their suitability for a landing pad.  I would have though some form of poured in place concrete would be better.

[lamontagne]

I was going to point it out in the Amazing Habitats thread, but the main issue for a colony spaceport (besides the direct main engine blast) is the dust being turned into a sandblast. Mars' low air pressure means the plume also extends pretty far. The MSL Skycrane plume started kicking up dust at 63m, excluding the cosine for the angled motors.
What prevented deeper excavation of the Skycrane craters seemed to be a layer of frost just below the surface.
Fortunately there's some atmosphere to stop the dust turning into a hypervelocity sandblaster.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150002954.pdf

Given that plume length is roughly proportional to nozzle diameter, the 63m dust-stirring height from 20cm Skycrane nozzles would scale up to 315 diameters,  ~500m for the Starship's Raptors, effectively blanketing the immediate vicinity in dust. So the spaceport design would have to account for that.

Could a pad cleaning system mitigate this sufficiently by removing most of the dust?   I agree that for the first few landings without prepared pads this would be a great risk, and that the ships will probably land a certain distance from one another because of this.  But can we clean a pad enough to make this problem disappear?  Or does pad erosion due to the exhaust plume create the same problem?

[lamontagne]

Moved from the Envisioning Habs thread:

How would a starship blowing up on Mars actually work? [...] How fast would a starship fully loaded with fuel and oxygen that breaches its tanks burn? [...] If just one tank is breached there wouldnt be any fire or explosion.

DO YOU BLEVE. (Doesn't even need to be a flammable gas.)

And such a rupture of one tank will cause a structural failure of the vehicle, causing the second tank to break open, even if just from falling debris, causing a second BLEVE, which will cause the two propellants to mix in a nice way for a final kablooie.

And if you are preparing multiple SS's (crew and cargo) near the pad for the return trip, with enough fuel stored nearby for all of them, a single failure of either an SS or one of the storage tanks, you'll take out the whole fleet in additional to all the fuelling infrastructure. And the base itself if you are close enough. The cost of an accident is so great, while the cost of adding an extra mile or two of distance between launchpad and base so trivial by comparison, it's crazy to just cross your fingers and hope that nothing goes wrong.

You have to plan for a major failure on Mars. Just as you have to plan your supplies on Mars around a failure on Earth grounding the fleet for long enough to miss at least one full synod.

This type of failure could happen at all times, I guess.  Not just at take off but at any time if the 'life' of a tank.  A Faulty valve, meteorite strike, weld failure, propellant transfer problems could all happen.

Might this be a reason to favor the construction of tanks made from in situ materials and sitting them away from one another, rather than using the Starships as propellant tanks?  Perhaps the first few ships will serve as tanks because there will be no alternative, but separate propellant tanks might be a priority?

[lamontagne]

Any opinions about the need of a flame trench on Mars?  A very strong pad is also pretty costly, so perhaps a minimum flame trench might actually save money?

And is there any gain in combining take off and landing operations onto a single pad or are these so different that the spaceport will have these functions separate?

One of the apparent gains of in-situ fabricated tanks is that ships can land, refuel and take of quickly, perhaps fast enough to return to Earth in the same synod?   It's always been an issue for me that the ships cannot realistically expect to fly 100 times if they are stuck on Mars for years at at time, while on Earth they can flight for other missions while waiting for the next synod?

[KSHavre]

I have been watching this conversation in a few threads, and see several ideas that make sense depending on the evolution of the Mars Base. I think I already saw #1 in an NSF post.

1. For the permanent Spaceport, ISTM that utilizing topography as much as possible gets you the most bang for your resources. IMHO looking for a Mars Base location above a bluff that faces away from the Base (Mars Orbiter Laser Altimeter data?) puts your Spaceport closer to the Base. Bonus points for finding one close enough in height to have the Cargo Door accessible from the top of the bluff! If not, bore a tunnel at the right height so that a drop-down bridge/door allows for driving cargo right out of the SS. That gives you warehouse and operations rooms bored into the bluff. Flame trenches could be dug out away from the pads to direct the startup energy away from the pads.

2. The "net' protection idea from the Amazing Habitats thread is very interesting. The old metal guard rails on heavy posts along roads did not work very well, and are being replaced by lots of smaller posts and cables; load is dissipated as the cables stretch. Use Kevlar type material for the netting?

2.a. For earlier pads, hang nets between a couple of {EDIT: kelvonzero's (not lamontagne's) idea for a couple sacrificed SS's as a barrier}
2.b. For more permanent pads along the bluff, hang a nets out between (3-4?) pads to protect other SS's along the land/launch pads.

[lamontagne]

Has Elon Musk explicitly stated that the first Starships will remain on Mars, or might they fly back when the fuel is available, one or a few synods later?

[rsdavis9]

I'm thinking we are seeing the prototype for a launch pad right now here on earth.
Large many wheeled vehicles to transport over ground.
Milk stool flame deflector with water?/co2?/other as coolant.
Crane to stack on milk stool.
We will know soon when they fire the SS at boca chica.
Either they fire from open ground or they make a milk stool.
In KSC we have already seen the plans for crane and milk stool.
We have seen the many wheeled vehicles at boca chica.

[DistantTemple]

I'm thinking we are seeing the prototype for a launch pad right now here on earth.
Large many wheeled vehicles to transport over ground.
Milk stool flame deflector with water?/co2?/other as coolant.
Crane to stack on milk stool.
We will know soon when they fire the SS at boca chica.
Either they fire from open ground or they make a milk stool.
In KSC we have already seen the plans for crane and milk stool.
We have seen the many wheeled vehicles at boca chica.

On Earth they are constrained by being in the US, existing locations, population, and often needing to be near the sea!
But on Mars there will be different choices. Close to Water/ice, and low latitudes, etc as frequently discussed... NASA discussions etc etc... But GOOD TOPOGRAPHY for landing SS in a valley, escarpments to dig into etc... (and therefor interesting geology... and likely a wider range of minerals etc for possible future extraction. If we had any idea of SX ideas for landing it would be soooo helpful.

[lamontagne]

I'm thinking we are seeing the prototype for a launch pad right now here on earth.
Large many wheeled vehicles to transport over ground.
Milk stool flame deflector with water?/co2?/other as coolant.
Crane to stack on milk stool.
We will know soon when they fire the SS at boca chica.
Either they fire from open ground or they make a milk stool.
In KSC we have already seen the plans for crane and milk stool.
We have seen the many wheeled vehicles at boca chica.

All I can say it that when I proposed using Boca Chica as an example I got told, pretty forcefully, that it was not a good example.  Looking forwards to the milk stool!  Will it have hold down elements, I wonder?

[DistantTemple]

I'm thinking we are seeing the prototype for a launch pad right now here on earth.
Large many wheeled vehicles to transport over ground.
Milk stool flame deflector with water?/co2?/other as coolant.
Crane to stack on milk stool.
We will know soon when they fire the SS at boca chica.
Either they fire from open ground or they make a milk stool.
In KSC we have already seen the plans for crane and milk stool.
We have seen the many wheeled vehicles at boca chica.

All I can say it that when I proposed using Boca Chica as an example I got told, pretty forcefully, that it was not a good example.  Looking forwards to the milk stool!  Will it have hold down elements, I wonder?

Its totally Elon. First principals,And clearly the cheapest.
ISTM that SS is much cheaper than expected. I think there will be more than 2 x SS in 2022, and more than planned in 2024.
That means more room/mass to bring heavy steel pieces, and heavy transporter etc.

[Hominans Kosmos]

Moved from the Envisioning Habs thread:

How would a starship blowing up on Mars actually work? [...] How fast would a starship fully loaded with fuel and oxygen that breaches its tanks burn? [...] If just one tank is breached there wouldnt be any fire or explosion.

DO YOU BLEVE. (Doesn't even need to be a flammable gas.)

And such a rupture of one tank will cause a structural failure of the vehicle, causing the second tank to break open, even if just from falling debris, causing a second BLEVE, which will cause the two propellants to mix in a nice way for a final kablooie.

And if you are preparing multiple SS's (crew and cargo) near the pad for the return trip, with enough fuel stored nearby for all of them, a single failure of either an SS or one of the storage tanks, you'll take out the whole fleet in additional to all the fuelling infrastructure. And the base itself if you are close enough. The cost of an accident is so great, while the cost of adding an extra mile or two of distance between launchpad and base so trivial by comparison, it's crazy to just cross your fingers and hope that nothing goes wrong.

You have to plan for a major failure on Mars. Just as you have to plan your supplies on Mars around a failure on Earth grounding the fleet for long enough to miss at least one full synod.

This type of failure could happen at all times, I guess.  Not just at take off but at any time if the 'life' of a tank.  A Faulty valve, meteorite strike, weld failure, propellant transfer problems could all happen.

Might this be a reason to favor the construction of tanks made from in situ materials and sitting them away from one another, rather than using the Starships as propellant tanks?  Perhaps the first few ships will serve as tanks because there will be no alternative, but separate propellant tanks might be a priority?

No, it could not happen. It can only ever happen as a consequence of highly unlikely circumstances. Never can it happen near to normal operating conditions such as launch. Propellant is always kept below boiling point, not above, during launch it's closer to freezing point. It would require both the temperature control, and pressure control (redundant overpressure relief valves giving access to evaporative cooling!) to fail at the same time. This is never going to happen.

A boiling liquid expanding vapor explosion (BLEVE, /ˈblɛviː/ BLEV-ee) is an explosion caused by the rupture of a vessel containing a pressurized liquid that has reached temperatures above its boiling point