Ballistic Delivery of Supplies to Mars: Lithobraking

tahanson43206 · 2021-01-18 22:56:57

This topic was inspired by one the many ideas of Void ...

SearchTerm:FAQ Ballistic Delivery of Supplies to Mars
SearchTerm:Ballistic Delivery of Supplies to Mars
SearchTerm:Lithobraking Term used by Isaac Arthur and introduced to NewMars by Void

The time to place supplies on Mars using ballistic techniques is after initial exploration, but before large scale population influx.

The issue raised by SpaceNut, upon reading Void's idea, is the loss of material when two solid objects collide at multiple kilometers per second.

The resulting pockmarks are visible on the Moon, at a number of locations on the Earth, and throughout the Solar System.

***
On Earth, scientists and engineers have been studying the penetration of matter by objects for many Earth years.

There is an entire field of science devoted to the subject, and in the post after this one, I will show an example of a study, along with a selected list of references.

The proposition of this topic (derived from Void's original idea) is that there may be a way to deliver supplies of raw materials to the surface of Mars using ballistic techniques without loss of material.

To be clear ... a ballistic material delivery system would NOT involve slowing the package of supplies before it impacts with the surface of Mars.

Instead, the package would be so designed that there would be very little material ejected from the site due to the collision, and NONE of the planned payload would be lost.

Solving this problem will require significant expertise and reasonably powerful computing tools.

it should ** not ** be beyond the state-of-the-art of ballistics science in 2021 on Earth.

Edit#1: 2021/01/22 It was brought to my attention that kinetic weapons are not just historical footnotes. Apparently they are still very much part of the armament capability of the United States and other nations. Because of the history and current status of kinetic weapons, there is a risk that study of the use of a kinetic payload delivery system for Mars will awaken unwelcome concern by some who are responsible for safeguarding the wellbeing of the citizens of their respective nations

I'd like to make clear that the proposed idea is intended for delivery of useful material to Mars for construction of equipment and shelter on that planet. It is recognized that the use of this method of delivering supplies must be regulated from the start, and even more strictly regulated after human visitors have taken up residence on the planet.

(th)

FAQ Frequently Asked Questions:

tahanson43206 · 2021-01-18 22:58:58

Here is an example of Ballistics Science research ... the specific study investigates the feasibility of using Artificial Neural Networks to reduce computing time when solving problems in ballistics.

I would expect such techniques to be useful in finding solutions to the challenge of ballistic delivery of raw materials (or refined materials) to Mars.

https://www.sciencedirect.com/science/a … 4715000021

Determination of penetration depth at high velocity impact using finite element method and artificial neural network tools
Author links open overlay panelNamıkKılıÇaBülentEkicibSelimHartomacıoğluc

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tahanson43206 · 2021-01-18 23:05:57

In a related line of thought ....

It may prove advantageous to deliver ballistic payloads to Mars into a previously excavated opening into the regolith.

The proposition to be explored is that if impact occurs at a sufficient depth below the surface, the energy released by the arriving payload mass will be absorbed by the regolith without release of material to the atmosphere.

A proof of concept is the use of buried nuclear weapons sites for testing during the Cold War on Earth. When nuclear weapons were buried a sufficient distance beneath the surface, the energy released by the devices was absorbed by the surrounding material, so that no material (or very little) escaped to the open air above.

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tahanson43206 · 2021-01-19 13:20:32

This text is from [Dayton Engineer]. [Dayton Engineer] probably will not become a member of the forum, but from time to time he allows me to ask him questions about topics under discussion in the forum.

In this case, I asked about Void's idea about impact delivery of durable supplies to the surface of Mars. I interpret the excerpt below as mild encouragement:

On the impact delivery techniques, I think there is some merit to the idea because the atmosphere of Mars is so tenuous. Aero braking can be used to reduce the energy of objects going into orbit around Mars, and also to reduce energy as the orbit is lowered and finally dunked into the atmosphere. The final deceleration to a soft landing may be limited by the thin atmosphere, so developing hard landing techniques will probably be a good thing.
Devices can be designed to take tremendous acceleration; the proximity fuses developed during Works War II is a good example. These electronic fuses used vacuum tubes, complete with their delicate filaments, but efforts ended up with small tubes that could take the 20,000 g’s or so felt as shells accelerated up artillery barrels.
The only problem with tightening things up for hard impact is the weight increase necessitated to survive the sharp deceleration. This comes back to bite when trying to inject these items into orbit around the earth and accelerate them towards Mars. Low mass is important on the departure and arrival ends to save propellant.
Bulk materials like solid ores might be the best thing to deliver by impact, as they won’t be as delicate as manufactured items.

(th)

tahanson43206 · 2021-01-19 13:31:05

The post above (#4) contains a hint of a possible way to look, regarding hard landings of supplies on Mars.

What I'm looking for, and hope will arrive in the form of a message at NewMarsMember # gmail.com, is a solution involving fluid dynamics modeling of the regolith of Mars, such that a properly pre-shaped receptacle on the surface (a depression) would permit an arriving mass to disperse its kinetic energy into the surrounding regolith, without damaging the payload, and without delivering material to the atmosphere above the site.

An excavated receptacle in the regolith would (presumably) have the desired capability, just as a properly excavated cavity below the desert in the Western US allowed for testing of nuclear weapons during the Cold War.

The energy cost of shipments of raw materials from Earth and from asteroids, comets and various moons would be greatly reduced if Mars itself could handle the details of deceleration.

The landing site would then become a mining location, much as the mine in Sudbury, Canada is a continuing source of high quality Nickel.

https://en.wikipedia.org/wiki/Creighton_Mine

Creighton Mine
From Wikipedia, the free encyclopedia
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This article is about the mine. For the ghost town, see Creighton Mine, Ontario.
Creighton MineCreighton Mine.JPG
Location
Creighton Mine is located in Ontario
Creighton Mine
Creighton Mine
Location of the mine within Ontario
Location Greater Sudbury
Province Ontario
Country Canada
Coordinates 46°27′50″N 81°10′29″WCoordinates: 46°27′50″N 81°10′29″W
Production
Products Nickel
Type Underground, originally open pit
History
Opened 1901
Owner
Company Vale Limited
Website vale.com
Creighton Mine is an underground nickel mine, owned and operated by Vale (formerly known as INCO) in the city of Greater Sudbury, Ontario, Canada. It is currently the deepest nickel mine in Canada.[1]

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Calliban · 2021-01-19 14:38:48

If the incoming projectile can be guided to a specific impact site to an accuracy of 1km, then I would propose an ice covered lake as an impact site.

If accuracy is to within 10m, then a deep pit filled with cold CO2 gas. As the projectile enters the pit it will transfer its kinetic energy into the gas, which will escape around the sides of the incoming projectile.

SpaceNut · 2021-01-19 18:10:53

All Mars entries start ballistic at an attack angle tanget landing site. The inward slide is shape / slowed be the surface area of the heat shield even though Nasa would then dump weight to change the pitch before the heat shield is chucked and the parachute would be deployed.
Designing with no parachute mass does change the slide rate a little but in the end the gravity will con tinue to accelerate the unit towards a high speed impact with an intact heat shield much like the appollo space crafts into a liquid wold slow it but then it would sing in the absence of an inflatable ring simular to HIAD.
Pin point landing is not happening due to atmospher anytime soon.

Not surprised to find Chemical Mars Lander Designs “Rough-Out”

That calls out Rough Correlation of Entry Ballistic Coefficient vs. Size for “Typical” Mars Landers

Velocity Requirements for Mars

https://en.wikipedia.org/wiki/Mars_landing

https://en.wikipedia.org/wiki/Ballistic_coefficient

https://en.wikipedia.org/wiki/Drag_coefficient

tahanson43206 · 2021-01-19 22:03:54

For Calliban (#6) and SpaceNut (#7) ...

It is good to see each of you taking up this new topic, which (I'd like to remind readers) is a product of the creative thinking of Void.

Calliban, thank you for your observations about the efficacy of properly designed landing "zones" for ballistic cargo carriers.

My brief/limited exposure to writings about military payload delivery gives me confidence that solutions for dealing with any kind of material are well studied and actually in practical use (if military applications may be characterized as "practical").

The huge bomb that was dropped in Afghanistan to deal with tunnels several years ago is a perfect example. That was precision guided munition dropped from a heavy lift aircraft.

***
For SpaceNut ... this topic is about delivery of cargo in the same manner as an artillery shell is delivered to a target. There is no parachute involved. There is no heat shield involved (although intercontinental ballistic missiles apparently do have heat shields).

The intent is to deliver a properly designed metal clad projectile full of valuable commodities into the regolith in such a way that no (or very little) debris reaches the surface. As Calliban has pointed out, a properly prepared entry point into the regolith can insure that inertial/kinetic energy of the projectile is dissipated into the surrounding regolith so that it does not create an impact crater or other evidence of the arrival.

It might help to think about nuclear weapons testing below the surface of the desert in the United States, and below the mountains in North Korea more recently. The idea is to dig a shaft into the crust of the planet to a depth sufficient to absorb the energy of the explosion so that nothing reaches the surface.

In the case of tests conducted in the desert of Western US, it was reported that the surface of the desert lifted at the time of the blast, and then settled back down, with a small amount of dust floating in the air afterward.

Something similar is what I am thinking about here, thanks to the creative thinking of Void, in another topic.

For SpaceNut regarding accuracy ... modern nuclear weapons are extremely precise. The inaccuracy you might be thinking of is the province of parachute landing attempts, which are subject to the vagaries of atmosphere. Modern nuclear weapons are not likely to be off target by more than a few meters.

(th)

SpaceNut · 2021-01-20 18:44:07

The File:Five301906govtBullets.png Ballistics are no where near the entry or dive speeds that Mars would and will see and since its coming in hot its going to get very hot and the craft does not spiral for gyro effect...

The wiki page gave the formulas for the drag on entry until impact no chutes or rockets which follows the Ballistic path towards the planet curving downward with the pull of gravity.

The only reason the air slows the ship is due to surface area.

to increase the surface area the hyper-cone is thought to give great aid in that arena.
planetary-space_small-launch-vehicle-1-e1477503142224.jpg

Accuracy of landing can be narrowed but it requires surface beacons

Trying to dissipate in regolith that is rock hard is a no go, ice covered lake would need to be covered to keep it there unit needed.

The orbital kinetic energy comes from the mass of the object, speed of it and the gravity of the planet.
ap-physics-c-gravitation-21-728.jpg?cb=1333540571

So all that is changing in the equation is atmospheric drag which is the thin atmospher....

tahanson43206 · 2021-01-20 19:25:10

For SpaceNut re #9

The kinetic energy equation in your post may prove helpful.

It seems that trying to use parachutes of nose cones is cluttering up this topic.

This topic is NOT about slowing the incoming payload prior to impact.

It is ALL about designing the shape of the regolith ahead of arrival of the payload so that the payload is absorbed into the regolith in such a way that the kinetic energy of the arriving package is dispersed to the material of the regolith so that NONE of the material of the regolith is lifted up into the atmosphere.

In order to understand the nature of the proposal, it would be useful to consult resources on ballistics, and specifically on design of projectiles intended to enter protected spaces through resistant material.

As Calliban has shown, there are options available to insure a payload arriving from off planet is "clean", and not disruptive, as a default arriving asteroid would be. The Moon, the Earth and Mars itself show what a default result of an arriving asteroid looks like.

This topic is about applying ballistics science to insure an arriving payload is absorbed into the receiving body in such a way that the kinetic energy is absorbed horizontally and vertically downward, and not back toward the surface.

Think of the difference between the entry into a body of water of an Olympic diver, and a cannonball specialist.

A default arrival of an asteroid looks like the cannonball diver, and there is regolith scattered widely, and there is a crater left behind.

A well design ballistic round leaves very little disturbance in the wall of a tank (for example) and continues on into the interior of the tank to complete its mission, whatever that may be.

(th)

SpaceNut · 2021-01-20 20:16:57

Regolith left open to the mars air will be filled with co2 moisture, water and will become hard as a rock with duration causing the depth to get even harder between uses....The higher the velocity and mass the higher the potential impact energy will be...

tahanson43206 · 2021-01-20 20:54:25

For SpaceNut re #11

Thanks for making the transition away from parachute delivery of supplies to Mars.

Your description of the receiving mass is interesting (to me for sure) as you are beginning to think about what a munitions scientist/engineer has to deal with.

In this case, we want to apply what has been learned to create "bunker buster" bombs for a much less ominous purpose ...

I know ** just enough ** about this subject to know that there are experts who have devoted their lifetimes to the study of how various kinds of projectiles interact with various materials.

What is intriguing (to me at least) is that in Void's creative thinking, he has overcome the blind spot that the rest of us have toward the subject of delivery of useful material to Mars.

I will ask [Dayton Engineer] for the name of an individual or an organization which might be willing to consider the challenge of designing payload delivery systems for the Mars expedition.

He has already indicated he's likely to be busy, so I'm not sure I'll get an answer, but I'll give it a try.

(th)

SpaceNut · 2021-01-20 21:03:56

Remember that if it goes deep into the landing site we will not be able to recover it due to energy requirement, safety of cave ins and more even if its still intact with weapons grade electronics which is doubtful to be supplied....
The bunker busters are meant to burrow deep with out anything to remain after it is miles deep...

tahanson43206 · 2021-01-20 21:11:20

Quoting Calliban's #4:

Calliban wrote:

If the incoming projectile can be guided to a specific impact site to an accuracy of 1km, then I would propose an ice covered lake as an impact site.
If accuracy is to within 10m, then a deep pit filled with cold CO2 gas. As the projectile enters the pit it will transfer its kinetic energy into the gas, which will escape around the sides of the incoming projectile.

I like your idea of a deep pit, but would invite your consideration of something a bit deeper ...

I'm thinking of a vertical (*) tunnel excavation, designed to admit the arriving payload so that it is well below the surface of the regolith before it begins deceleration. For this to work I am assuming pinpoint accuracy, which I understand to be well within the capability of modern military munitions.

Because you are the only working engineer in the group ( a retired engineer who is still "working" would be fine as well) I'm hoping you may have a friend who knows someone in the munitions business, and who would be willing to think about this problem as a business opportunity.

There are lots of useful materials that could be delivered to Mars using this technique.

It might even turn out that mining the delivered mass while it is still warm would be worth considering. If it is allowed to cool it will weld itself into a ball that will be more difficult to remove than might be possible otherwise.

(*) the angle of the tunnel might well be other than vertical. It might turn out that the optimum angle for a capture tunnel would be well off vertical.

Payloads coming in from Earth will (if on one of GW Johnson's Hohmann orbits) would be ahead of Mars and "waiting/coasting" for Mars to catch up.

Mars is rotating underneath. The path of the payload could be set to any of a range of angles.

The small mass of the atmosphere could be used to fine tune the trajectory of the capsule.

A tunnel used for a delivery could (presumably) be used again, after the first payload has been removed.

The Insight Marsquake detector would have plenty of data to send home.

(th)

SpaceNut · 2021-01-20 21:33:50

Any void it finds along the path will mean it can bridge it and become cross tunnel stuck.

At 6 - 8 miles still above the surface a 5m aero shell structure has brought the incoming from its 12,000 mph down to just under 1,000 with not all that long before what we would send will find the surface....

I will see if I can find the dissipation for the remain time and impact speed If I can find the equation which is the LD portion of the entry to mars just continued all the way to the surface.

Calliban · 2021-01-21 06:43:20

Approximation of impact depth for a blunt projectile in a medium with limited cohesion.
https://en.m.wikipedia.org/wiki/Impact_depth

Basically, it depends upon the relative density of material and the length of projectile. You can use this to estimate g-forces in deceleration, if you know the impact velocity.

Let us assume a projectile density of 5000kg/m3; regolith density of 2000kg/m3 and projectile length 1m. Penetrative depth will be 2.5m. Assuming initial velocity of 1000mph (450m/s) (from Spacenut), average deceleration on impact would be 40,500m/s2 (4100g) for 0.01 seconds. Maybe someone could look into what payloads can and cannot tolerate that. According to wiki, mechanical wrist watches can and even some electronics can.
https://en.m.wikipedia.org/wiki/G-force

One idea for reducing projectile velocity less rapidly: an ejector tube. We build a tube a few hundred metres high and aim the projectile for it. A second before impact, we release liquid CO2 into the tube, which boils explosively, producing a stream of cold pressurised gas expanding out of the tube at 200m/s. The projectile will experience extreme aerodynamic drag as it approaches the tube, slowing its terminal speed dramatically. In fact, depending upon the angle of dispersion on the plume in the think Martian atmosphere, deceleration could begin some distance above the tube. If speed is reduced from 450m/s to zero over a distance of 1km, average deceleration would be 10.3g for a period of 4.4 seconds. OK for humans, although the timing would need to be precise.

Something similar might be used to slow landers on Luna, using sulphur dioxide or oxygen. We could perhaps use a small amount of gas to blow lunar fines into the path of an incoming projectile. The projectile would carry a drag chute that would transfer momentum to the fines.

Last edited by Calliban (2021-01-21 07:33:20)

tahanson43206 · 2021-01-21 07:27:41

For Calliban and SpaceNut ... thank you for helping to build this topic.

I am hoping it will be valuable to Mars settlement planners. As a reminder, this topic is a development of an idea posted by Void in another topic.

***
To (try to) clarify ... the proposal is NOT to use the atmosphere as a way of slowing the projectile. It would (instead) have potential value as an agent to fine tune the trajectory of the package as it heads toward a previously prepared destination.

A potential previously prepared destination is a tunnel excavated at the needed angle to match the optimum trajectory for the arriving package.

The actual velocity would be a combination of the velocity of Mars as it approaches the package from behind, as the package coasts up on a Hohmann orbit, and the acceleration imposed by Mars' gravity. GW Johnson has given exact numbers for those velocities elsewhere in this forum on multiple occasions, as well as in his blog (ExRocketman).

I am now working from the information provided by Calliban in #16 ... We (humans) have data on the nature of the surface of the regolith of Mars, thanks to the multiple probes that have been exploring there.

While (it seems to me) we can't be certain, the density of the material under the regolith surface ** may ** be similar.

If we assume a prepared receptacle dug into the regolith of (arbitrary number: 10 meters) then the equation given by Calliban should reveal the depth below the bottom of the tunnel to which the payload will carry itself.

The energy arriving with the payload will be distributed in the regolith around the point of impact. A properly designed receptacle will insure that no ejecta reaches the surface. It can be anticipated that the surface will rise momentarily as shown by underground nuclear explosions in the Western US.

The tunnel itself may remain open or it may fill up ... at this point I think that only modeling using fluid dynamics software can provide a clear picture. The various military science organizations around the world may well have repositories of research (a) and (b) actual experience to allow for prediction.

There are NO costs associated with attempts to slow the package at is approaches Mars.

There ARE some expenditures of mass and energy to fine tune the trajectory of the package as it approaches Mars. A properly designed mission will have minimal requirement for such fine tuning.

The fine tuning of the trajectory during flight through the atmosphere to achieve 1 meter accuracy would involve modest airfoil actuation, and the electronics on board to control them, using position data delivered to the vehicle from ground support radar.

The only costs that I can see are on the ground, where the arriving payload will bury itself in the regolith below the tunnel entrance. If the tunnel remains open after the package arrival, then payload retrieval would be easier. Otherwise the tunnel would have to be re-excavated. However, the material that would fill the tunnel (assuming that occurs) would NOT (*) be compacted above the location of the payload.

(*) The above is a guess of course.

For SpaceNut ... thanks for the arrival velocity figures. If you can find GW Johnson's exact figures, it would be helpful. What I am looking for are:

1) The velocity of Mars with respect to the payload coasting up from Earth on a Hohmann trajectory
2) The acceleration of Mars that will cause the payload to reach its ultimate velocity at the time of impact

With that velocity, and the equation provided by Calliban, it should/may be possible to compute the depth of the tunnel needed for management of delivery packages of various masses and lengths.

The results of the study should be invariant. The mass of Mars is likely to remain constant for a few hundred years.

It should be possible to build a strong business case in favor of this method of delivering supplies to Mars in anticipation of the needs of arriving settlers.

(th)

Calliban · 2021-01-21 08:04:30

Tahanson, I think much depends on what the impact velocity would be. If it is 500m/s, then we could probably engineer projectiles and dumb payloads that will survive a rapid deceleration in regolith. If it is 5km/s, then it is far more doubtful. A prepared landing site or tunnel won't be free either.

From what little I understand of achieving a Mars landing, it is relatively expensive to achieve a soft landing because the Martian atmosphere is thin and gravity is substantial. Above a certain payload size, it becomes impossible to achieve a soft landing using parachute alone. The systems employed for Opportunity were quite complex. But I would suggest that between a purely ballistic impact from an artillery shell and soft landing, there is a spectrum of solutions that would make use of atmospheric drag to varying degrees, depending on what we need to land. Atmospheric drag will inevitably reduce the speed of any entering projectile. So the question becomes, what is the optimal design solution for the payload we want to deliver? It could be a bulked up (inflatable?) heat shield, that reduces the areal density of the payload, or maybe a drag chute that reduces impact velocity to an acceptable level. Or maybe at the base building stage, we can prepare an impact site on the ground - a covered pit or crater full of something with low density. Ultimately, the cheapest way of meeting the design requirement is the option that wins.

tahanson43206 · 2021-01-21 08:17:01

For Calliban re #18

Thank you for your review of the range of options for payload delivery to Mars.

SearchTerm:Payload deliver to Mars Options Calliban http://newmars.com/forums/viewtopic.php … 86#p176086
SearchTerm:Options for delivery of payloads to Mars, from soft landing to full impact

You are right of course. I am trying to advance this contribution by Void to give it as much room to blossom as the Universe will allow.

In a few days, the exact numbers previously provided by GW Johnson (and others before him) will become available in this topic.

At that time, it will be possible for experts in munitions used for military purposes to evaluate the potential of full impact delivery of materials to Mars, or potentially other interesting locations, such as the Moon.

None of the atoms used to make regolith penetrators will be lost! ** Every ** atom will be recoverable. If depleted Uranium (as just one example) is found to be the optimum outer coating for a package, then all those atoms will be available, for whatever use they may have.

I'm assuming the word "depleted" means the Uranium is no longer suitable for use in a reactor, but since it obviously is useful for military ballistics, it may have uses on Mars.

Regarding costs of mining ... I expect the costs of mining delivered supplies will be comparable to costs for mining of insitu materials. The difference would be the miner knows ** exactly ** what atoms are available to be retrieved, while a miner of unknown material is making a calculated bet with every cast of the net.

Edit#1: This is primarily for Calliban, but anyone with knowledge of munitions, physics of chemical explosions, and any other related field of study is welcome to help out .... In thinking about Calliban's post, and the topic in general, I realized that there is an option that opens up once we've freed ourselves to seriously consider a ballistic delivery scenario.

A military device of the type we are thinking about often (if not usually) contains a secondary explosive that is intended to be delivered into the interior of a protected space, such as a tank, a bunker, a ship or most anything someone would want to protect.

In the case of a Mars Ballistic Package Delivery service, that munition could have a (to me at least) surprising application ...

A payload that is needed on the surface could be ejected back to the surface, as the lead edge of the carrier begins to engage with the regolith.

I am imagining a spring (probably a gas) that is sitting between the head of the carrier, and the high value payload to be delivered to the surface.

Upon engaging with the regolith, the forces of deceleration would be enlisted by the spring to eject the payload back up the receiving tunnel, so that it lands gently at the rim of the opening, where a radio transmitter would announce its safe arrival.

The valuable materials contained in the carrier could be retrieved by traditional mining operations later.

What I'm thinking about here is the kind of valuable payload NASA would be happy to have safely delivered to Mars for their use in scientific exploration.

Such a payload might be (as just one example) a replacement nuclear thermal package for an exploration vehicle

Depending upon the ability of electronics to withstand the G forces we are considering in this topic, the payload might even be a replacement computer or perhaps a solid state memory device to supplement one that was filled up by the exploring device.

(th)

SpaceNut · 2021-01-21 18:33:10

Dragons return from orbit starts in a ballistic fashion requiring even with a slower entry a heat shield.

The values are distance and mass dependent from the point of leaving earth and the thrust of the engines to get it on its ways to mars.

https://www.spacex.com/vehicles/starship/

Starship will enter Mars’ atmosphere at 7.5 kilometers per second and decelerate aerodynamically. The vehicle’s heat shield is designed to withstand multiple entries, but given that the vehicle is coming into Mars' atmosphere so hot, we still expect to see some ablation of the heat shield (similar to wear and tear on a brake pad).

https://en.wikipedia.org/wiki/Atmospheric_reentry

of course the Red dragon would have been a first attempt for a retro propulsion
https://en.wikipedia.org/wiki/Red_Drago … cecraft%29
http://images.spaceref.com/fiso/2016/09 … -21-16.pdf

https://www.reddit.com/r/spacex/comment … mes_study/

tahanson43206 · 2021-01-21 19:47:19

For SpaceNut re #20

Thanks for links about Starship and various soft landing techniques.

This topic is reserved for discussion of hard landings.

In post #19, I introduced a concept that becomes a possibility once we've allowed ourselves to leave parachutes and heat shields behind in our thinking.

If you'd like to help, you can find references to ballistics research, showing projectiles passing through various materials and leaving very little waste behind.

What Calliban has suggested is a deep depression into which the arriving package would descend, so that at impact it is already below the level of the terrain. I am building on the suggestion by following up with a concept of a tunnel dug at an angle to match the angle of flight of the arriving payload.

In that scenario, the payload would enter the tunnel at whatever speed we determine from GW Johnson's previous computations, is the sum of the velocity of Mars as it comes up behind the delivery package which is coasting up from Earth below, and the gravitational attraction of Mars itself.

That sum will be the velocity of the package as it enters the regolith receptacle on its way to the bottom, where the tip of the projectile will begin to interact with the regolith.

The idea introduced in Post #19 is to include a chemical "launch" subsystem in the vehicle designed to accelerate the payload back along the line of flight, so that it pops out of the tunnel at the level of the terrain with zero (or near zero) relative velocity.

The balance of the mass of the package would continue to interact with the regolith until all the kinetic energy delivered by the carrier is distributed in the regolith.

(th)

SpaceNut · 2021-01-21 20:51:32

The heat shield for starship is for the heat to be absorbed and then in the engine plume on earth returns from orbit after the heat shield does its job to control heating which you will not get with this design and due to the heat of speed from entry all the way down to that 10 mile high location the ship will melt/burning off until where the speed has finally begun to drop from entry speeds so that the metal is cooling in the thicker atmosphere.
This is physics of atmospheric entry.....

tahanson43206 · 2021-01-22 06:22:47

For SpaceNut re #22 and topic in general

Thanks for continuing to support this new topic, especially in its early stages when it is just getting started

This topic is NOT about heat shields, although the example of ballistic missiles on Earth suggests some heat shield may be necessary to achieve the objective.

An asteroid approaching Earth, Mars, the Moon or any other body does not depend upon a heat shield to deliver the bulk of its mass to the surface.

I notice in composing the statement above I have overlooked a category of smaller object that can be observed to consume itself in the atmosphere due to collisions with molecules (in the case of Earth) of air. Meteors may or may not reach the surface of the Earth, depending upon the size of the meteor, the material of which the meteor is "made", and the combination of velocity and duration of the passage.

Perhaps I can help you make the needed transition to be able to accept this topic, by imagining we are interested in delivering meteors all the way to the surface of Mars.

The question to be answered (in the case of meteors) is: What size of meteor can survive passage through the atmosphere of Mars?

A meteor is an object that is not "designed" to travel through the atmosphere of any body, so it does not have a shape that is optimized for success.

A ballistic missile warhead ** is ** designed to not only survive but to arrive at it's destination fully intact and fully operational.

This topic may include discussion of a heat shield at some point, but at THIS point, the question set that needs to be filled in includes such items as:

1) What velocity is to be planned for? The flights of the various NASA (and other) probes may be helpful as guides.

Your example of 7.5 km/second may be in the ballpark, although that is a projection of the velocity SpaceX planners are anticipating.

2) What shape is optimum for successful delivery of the desired amount of mass to the surface

3) What material is best able to handle the collisions with Carbon Dioxide molecules on the way in?

4) What trajectory is optimum for this application?

To the best of my knowledge, these are questions never posed before, because (again, to the best of my knowledge) no one prior to Void has asked if a ballistic delivery is possible, let alone economically practical.

At this point, I am taking the position of an optimist, that Void's idea is practical (until proven otherwise) and that it represents an investment opportunity for one of Quark's friends with deep pockets and a tolerance for elevated risk.

There is only one way to know for certain, and that is to deliver a projectile to the surface of Mars to see how much survives.

It may be possible to run software emulations that will provide insights into optimum shapes and materials for the projectile to maximize survival after passage through the atmosphere of Mars at various speeds and for various durations.

It may be possible to run software emulations of impact of such a projectile with the regolith of Mars, using various shapes of receptacle cavities. The goal in that case is to find solutions that result in little or no debris delivery back to the surface.

***
Fracking ...
***

Perhaps the arriving projectile can have a secondary value ... The arriving projectile will have a kinetic energy due to its mass and its velocity that will be absorbed by the regolith and distributed for some distance into the material around the "landing" site. This thermal energy may have a beneficial effect from the standpoint of humans looking for desirable materials to become available, such as steam or other gases that might become available.

However, I remain interested in the possibility a payload riding in the trunk of the primary object can be given a rearward push at the moment of impact such that the payload is delivered safely and gently back to the surface for retrieval by the waiting recovery team.

There is a long established field of human science dedicated to answering questions like these. For hundreds of years, humans have been studying the science of ballistics, and the science has reached very advanced stages at this point.

(th)

Calliban · 2021-01-22 09:37:49

The escape velocity of Mars is 5km/s. So any incoming projectile will hit the atmosphere with at least that speed. That is about 5-7 times the speed of an assault rifle bullet, with 25-50 times the amount of kinetic energy per unit mass. It equates to a kinetic energy of 12.5MJ/kg. The specific heat of steel is about 0.4KJ/kg.K and it melts at 1600C. So if even a tenth of the incident kinetic energy heats the projectile due to friction on impact, it will melt it, and it will end up being mixed with other material at the impact site, some of which will be ejected.

Without detailed modelling, I would suggest that the specific energy of a solid steel projectile cannot be much greater than 1MJ/kg on impact with the surface if you want it to remain reasonably intact. And that is for a solid steel projectile. It equates to an impact speed of 1.4kms. So if you want to deliver bulk amorphous materials with high melting point, 1.4kms is about your limit. For other goods like electronics, solid components, food, industrial chemicals, etc, even a 500m/s impact velocity will expose the impactor to forces of 5000g in soft soil. So I think 500m/s impact speed is a sensible limit for hardy components.

Either way, you need to slow the projectile down quite a bit if you want it to survive in any form when it impacts the surface. It needs to lose at least 99% of its incoming energy prior to impact for hardy goods and at least 90% for bulk amorphous materials, like iron, copper, etc, unless you want them dispersed and scattered in lumps of molten rock. The cheapest way of doing that is using atmospheric drag, which means a heat shield. It doesn't necessarily have to be complicated. We may be talking about something as simple as a steel sphere covered is some sort of sintered ceramic.

tahanson43206 · 2021-01-22 10:13:36

For Calliban re #24

Thank you for giving Void's idea a lifeline! I'd like to see it succeed in some form, if it is possible.

Void has contributed many (if not many many) creative ideas to this forum over a number of years, and some (like this one) seem (to me at least) to have potential to become entire industries.

SearchTerm:Impact numbers per Calliban http://newmars.com/forums/viewtopic.php … 16#p176116

Related: Arrival velocity of Starship (estimated) per SpaceNut: http://newmars.com/forums/viewtopic.php … 01#p176101

It is possible you (as a working engineer) have the knowledge and experience needed to develop this concept as far as it can go. What seems equally likely is that you are fully engaged with career, family and numerous other pro bono activities beyond this forum.

Can you think of anyone, or an agency or organization, that might be interested in making the necessary investments to determine if this idea is feasible (a) and potentially profitable (b).

It is entirely possible that major Nations who are engaged in Mars exploration would be willing to purchase a supply of atoms from a vendor, if those atoms are delivered to Mars at a location specified by the customer, and in a condition acceptable to the customer.

Regarding survival of electronics under momentary G loads ... My understanding is that electronics has been able to survive up to 20,000 G's in artillery shells for many (six or more) decades. It should be possible (speaking from a place of conjecture) to design a delivery system so the payload package is cushioned so the force experienced by the payload is within the tolerance specified by the customer.

In an earlier post, you provided a hint about where to look for solutions.... the equation you provided included a length term for the projectile impacting the receiving material. A projectile designed to be long and thin should be able to cushion the shock of "landing" as it collapses according to plan at a rate that allows the payload to survive. The atoms of the carrier are expected to be dispersed in the regolith cushion, from which they can be mined later.

In earlier posts, I have suggested that it might be worth investigating to see if a reverse launch capability might be built into the projectile package so that the payload is not only cushioned, but actually accelerated backward at a velocity sufficient to allow it to travel back up the intake tube/tunnel and arrive at the surface unscathed.

If there is someone knowledgeable about munitions and interested in exploring this topic, you are welcome to write NewMarsMember * gmail.com.

Please clarify you are writing about ** this ** topic, and not applying for membership in the forum (unless you are (of course)). (th)

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