Ballistic Delivery of Supplies to Mars: Lithobraking

tahanson43206 · 2021-01-22 10:25:51

For Calliban re topic ....

Gunpowder is a slow burning chemical mixture capable of delivering massive cannon balls from the exit port of a massive cannon. Such cannon were developed to remarkable size in the 18th and 19th centuries.

Imagine one of those 18th century cannon traveling at SpaceNut's (SpaceX's) 7.5 km/s with the breech end headed for Mars, and the port end pointed back along the path of travel. The objective is to cause a cannon ball packed above a supply of gunpowder in the breech end of the cannon to pop out of the tunnel with a velocity that matches the forward (toward Mars) velocity of the package.

Is it possible that a combination of components could yield a cannon ball with relative velocity of zero with respect to the surface of Mars, after the cannon itself impacts with the (prepared) regolith cushion at (using SpaceNut's (SpaceX's)) figure of 7.5 km/s?

If there is an expert in munitions who would be willing (and able) to assist, please write NewMarsMember * gmail.com

The cannon itself would become dispersed in the regolith for later retrieval as atoms of whatever alloy is used to make it, mixed with the regolith.

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SpaceNut · 2021-01-22 17:33:27

The speed of arrival has to do with the earth escape velocity which is as I indicated very high and not slow for entry into mars atmosphere...

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

An alternative expression for the escape velocity particularly useful at the surface on the body is: where r is the distance between the center of the body and the point at which escape velocity is being calculated and g is the gravitational acceleration at that distance (i.e., the surface gravity).

https://www.nasa.gov/audience/foreducat … ocity.html

A spacecraft leaving the surface of Earth, for example, needs to be going about 11 kilometers (7 miles) per second, or over 40,000 kilometers per hour (25,000 miles per hour), to enter orbit.

At which you are going to add more velocity to break free of earths gravity well to go to Mars.

https://nasa.fandom.com/wiki/Escape_velocity

The Tyranny of the Rocket Equation

tahanson43206 · 2021-01-22 18:39:35

For SpaceNut re #27

Is there a relationship between Earth Escape velocity and Mars Escape velocity?

This topic is about delivering a payload to Mars without using a parachute or any other device or system intended to slow the rate of progress toward the surface of Mars.

The rate at which a vehicle leaves Earth would seem to concern Earth.

The rate at which a vehicle approaches Mars is a function of its gravity, and in a recent post the escape velocity from Mars was included.

The rate at which Mars approaches an object coasting up from Earth on a Hohmann orbit has been posted on numerous occasions in this forum, by GW Johnson in particular and by others.

The rate at which a vessel arriving from Earth is traveling at the time of impact is the sum of those two velocities.

In a recent post you gave an estimate (provided by SpaceX) of 7.5 km/second for that velocity.

That number appears to be reasonably stable.

A ballistics engineer will be able to work with that velocity to design a vehicle capable of performing the landing mission as I have described in previous posts.

Thanks for keeping the topic going!

(th)

SpaceNut · 2021-01-22 20:37:51

Next thing up is the mass at entry into the outer atmosphere which is made from the protective shell that must be able to not only take the heat of descent and later the impact of kinetic energy into a loss medium with the critical payload contained with in it. The additional medium in between the payload and the shell is an absorbing and insulating gel or other resistant mass to both conditions.

How Do You Estimate Impact Force? How do you calculate the force of a falling piano?

piano_impact_force_for_different_collision_times_dropped_from_50_feet_png.jpg

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

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

Stainless, Titanium, come to mind for the protective casing but could we mix the layers with kevlar
so what are the strongest high temperature metals....

tahanson43206 · 2021-01-22 21:33:02

For SpaceNut re #29 ....

Thank you for your very nice follow up to the theme of the topic! The link I particularly enjoyed reading was the kinetic one, but the second (bunker buster) was interesting and enlightening as well.

The first was interesting (to me for sure) because it highlighted the career of Dr. Jerry Pournelle, who I got to meet while we were attending a meeting of the L5 Society in San Francisco. He was a very senior member of the leadership, and I was on the bottom rung of the ladder. Bob Heinlein was still alive at the time, although looking his age.

These Wikipedia articles show how much serious work has been done by the US and many non-US nations to develop kinetic weapons.

I was surprised to see that a kinetic weapon was deployed from a drone in 2020. This weapon type obviously remains very much part of the armament of modern nation states.

A concern that comes to mind as I reflect on this history, is that an initiative to develop a kinetic payload delivery system for Mars might be misunderstood, and all sorts of ITAR regulations and over sight would fall on the effort.

Charming!

All that said, thanks ** very ** much for your (to me amazing) search abilities!

***
Something to remember is that the atmosphere of Mars is much less substantial than the atmosphere of Earth.

I note from the Kinetic article that much of the orbital velocity of the kinetic weapon was anticipated to be lost due to resistance by Earth's atmosphere. The amount of resistance imposed by the atmosphere of Mars would be much less.

I noted as well that the designs featured telephone pole shapes so that the cross section of the device was small compared to the overall volume. That feature would help to insure the maximum payload delivery to Mars.

I expect that the survival of the material comprising the kinetic weapon is not of particular interest to Earthly weapons designers, whereas design for the Mars payload delivery application would be ** completely ** influenced by concern to maximize retention of the material in as compact a volume as possible.

The kind of material that would be of great value on Mars would be pure metals of various kinds. At this point (it seems to me) no one (on Earth or otherwise) has much of an idea how practical this idea will turn out to be.

The psychological considerations around developing a system based upon this concept may turn out to be more difficult than the physics, which may turn out to be simple in comparison.

Well, that's how it is with one of Void's ideas ... He opens the door to possibility, and it may turn out to be pandora's gateway as easily as not.

Edit#1: SpaceNut ... I went back and added text to the top post in this topic: http://newmars.com/forums/viewtopic.php … 04#p176004

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tahanson43206 · 2021-01-23 09:53:00

For SpaceNut re support of topic ...

On behalf of Void, who is not hear to speak for himself, I would like to thank you again for your significant support of this topic, in general, but specifically for Post #29. In thinking about your post, and the topic as it is progressing, I had an insight over night that will (hopefully) greatly increase the chances of the topic advancing to serious consideration for Mars Settlement Mission Planning.

To my knowledge (admittedly not comprehensive) no one anywhere (else) has come up with this idea, and it is only due to the presence of Void that ** we ** have it to work with.

So! In earlier posts and other topics, GW Johnson led discussion that led to the insight that if a vehicle coasting up from Earth on a Hohmann trajectory navigates it's flight so as to arrive just as Phobos swings around Mars in receding mode, the net velocity difference is on the order of 2 km/second. It is slightly more but I can remember the nearest whole number, so this post will work with 2 km/sec.

** That ** is an impact velocity that is very likely to be manageable by human military engineers for maximum performance of an arriving projectile (measured by the amount of super-valuable payload that is delivered intact to the destination). That is still a number that cannot be achieved by any organization less than a Nation State (with exceptions I expect to discuss in later posts).

However, the nature of Phobos itself may be nearly ideal for the purpose of delivery of substantial quantities of suitably chosen supplies to Phobos instead of Mars itself.

In other topics, the systems that would be needed for travel to and from Phobos have been thoroughly worked out. I consider that to be a settled matter, but am prepared to have suggestions offered for even better solutions as they become available.

So now we have dramatically reduced the size of the challenge to our (hypothetical) military engineering team ... we want to be able to deliver substantial quantities of valuable supplies to Phobos, in support of massive numbers of settlers on Mars. If my guess is right, that Phobos is a big soft target, perfect for accepting incoming rounds of supplies with grace and (ahem) warmth, then we should be able to find an audience to pursue the proposal with some enthusiasm.

So! Thanks again for your recent substantial boost to the topic!

(th)

SpaceNut · 2021-01-23 18:26:47

Speaking of things that smash into in this case a mountain under the sea with a hull

The much thick strong material shell is mass thats launch from earth that takes away from the paloads we can send in a launch to mars.
The on obit mass is currently 15 mT to get the 2 mT and even with a changed landing tactic its likely not to improve.

tahanson43206 · 2021-01-23 18:46:18

For SpaceNut re #32

Thank you for pointing out the hidden value of this proposal!

The much thick strong material shell is mass thats launch from earth that takes away from the paloads we can send in a launch to mars.

The carrier ** is ** the payload! The high quality materials used for the casing are NOT lost, in any way, shape or form. The atoms are ALL saved right in the regolith, waiting for retrieval by the ground team.

The high value payload is separate from the main deliverable, which is atoms needed for construction of buildings, vehicles, engines, and whatever else needs atoms not available on Mars at all, or which are difficult to obtain.

Thanks again for continuing to advance the topic!

Nothing is wasted in this scenario.

***
Enjoyed the images of the Naples pier and other sea side locations on Earth
***
Appreciated the image of the dented prow of a submarine whose captain either lost his way or had deficient maps of the sea floor in his route.

(th)

kbd512 · 2021-01-23 20:16:38

If the payload can maintain enough aerodynamic lift at Mach 2 to travel in a mostly horizontal direction at the point in time that it would otherwise impact the surface of Mars, then perhaps a relatively simplistic system like an aircraft carrier's arresting gear (on steroids, obviously) can bring the payload to a halt over ten seconds or so.

Is there a way to dive towards the ground to build up enough speed to produce sufficient lift, pull up at the last second, and then be traveling horizontally, so a hydraulic or electromagnetic brake could jerk the payload to a halt over enough time to keep the deceleration forces manageable?

We could use an arresting barrier like the ribbon-like nets we use to catch jets with broken tail hooks on the aircraft carrier and we would add a sensor to trigger a series of electromagnetic guns to rapidly accelerate the arresting net forward at the exact right moment, such that the payload / vehicle doesn't impact the net at Mach 2. If that's too complicated, then we use a series of very thin CNT tapes to progressively decelerate the payload, snapping some of them until we halt the forward motion of the payload.

If we can generate usable aerodynamic lift to land at Mach 2, then we don't need parachutes or retro-rockets or landing gear, which would drastically simplify the design of the reentry vehicle, as well as eliminating the weight associated with those systems. However, we probably need a reinforced airframe to handle the deceleration forces.

tahanson43206 · 2021-01-23 20:39:34

For kbd512 re #34

Thanks for ** another ** (to me surprising) branch from Void's original idea!

Your suggestion reminds me of a chap I met (on the Internet) while searching for the cost of electricity to lift a payload to orbit, if a space elevator were possible.

My recollection is that he had computed some ridiculously low amount, using simple physics and the cost of electricity in his location at the time.

In the course of interacting with him (first name was Jim ... ) I learned he'd "invented" a system that was a variation of the (somewhat famous) launch loop idea that was published in the L5 News back in the day. The idea involved a flight path for a vehicle from Lunar L1 around to the back side (away from Earth) where it would encounter an electromagnet track designed to collect energy from, the vehicle and slow it to a stop. The concept was to store the energy and use it to launch the vehicle from the same track, so that it looped back to L1.

I thought then and still think that was a remarkably prescient idea, which may come to pass some day.

Your idea (in this case) is similar, in that an electromagnetic track would catch the arriving vehicle/cargo pod and collect energy while slowing the vehicle.

In this case, we don't have a concept in mind for launching the vehicle, so the energy collected would be available to the community to use as needed.

One observation I would make is that the vehicle is going to be white hot due to travel through the atmosphere of Mars, thin as it is.

Heat wouldn't necessarily make any difference to the electromagnetic track, since the encounter time at any given magnet would be short, but (I would think) the vehicle/pod would still be white hot after it is slowed. it will need some time to cool, away from combustible objects.

I'll probably remember Jim's last name overnight. It's been almost 10 years since I last "talked" to him.

Edit #1: The gent's last name was/is Cline ... as far as I know he is still with us ...

Here is a collection of snippets from Google:

Elevator Carousel d | Force | Classical Mechanics - Scribd
www.scribd.com › presentation › Elevator-Carousel-d
Carousels vs. Space Elevators James E. D. Cline. Exploring the similarities and differences between the anchored tether earth Space Elevator concept and the ...
Characteristics of Space Escalator Carousels vs Space ...
www.scribd.com › document › Characteristics-of-Space...
Characteristics of Space Escalator Carousels vs Space Elevators - Free download ... Cline, James E. D. “Comments and alternatives, by Jim Cline, regarding the ...
Lunar space elevator - Wikipedia
en.wikipedia.org › wiki › Lunar_space_elevator
In 1972, James Cline submitted a paper to NASA describing a "mooncable" concept similar to a lunar elevator. NASA responded negatively to the idea citing ...
Building Up: The Novelway Prototype Shop, Crisis ... - Bookshop
bookshop.org › books › building-up-the-novelway-pro...
This first of the four science fiction novels by Jim Cline centers around the adventures of building the first Anchored Tether Space Elevator, the first...
Building Up – a book by Jim Cline - Smashwords
www.smashwords.com › books › view
Their corporate bosses have given them a dangerous job intended to fail - the building of the first small Space Elevator - but when they succeed at that task, they ...
Building Up by Jim Cline | NOOK Book (eBook) | Barnes & Noble
www.barnesandnoble.com › Books
Jul 1, 2009 — Their corporate bosses have given them a dangerous job intended to fail - the building of the first small Space Elevator - but when they succeed ...
Rating: 4 · 1 review
James E. D. Cline · Building Up: the Novelway Prototype Shop ...
igames.dk › Books › James E. D. Cline
This first of the four science fiction novels by Jim Cline centers around the adventures of building the first Anchored Tether Space Elevator, the first wheel-type ...
Building Up eBook by Jim Cline - 9781452401126 | Rakuten Kobo ...
www.kobo.com › Kobo Books › eBooks › Nonfiction
... Cline available from Rakuten Kobo. Their corporate bosses have given them a dangerous job intended to fail - the building of the first small Space Elevator...
Building Up: The Novelway Prototype Shop ... - Goodreads
www.goodreads.com › show › 7626003-building-up
This first of the four science fiction novels by Jim Cline centers around the adventures of building the first Anchored Tether Space Elevator, the first wheel-type ...
Thoughts on Space Elevators - Blaise Gassend
gassend.net › spaceelevator
Why the Space Elevator's Center of Mass is not at Geosynchronous altitude ... A page by Jim Cline that got me thinking about reel-to-reel buildup, and a local ...

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SpaceNut · 2021-01-23 21:42:00

Which is the other topic which is moving payload out of the starship so that it can land on an unprepared surface area.

Normally payload is only the cargo and not its canister or shell that delivers it but in this scenario we are wanting to recycle that part as regather at energy expense for its recovery.
Hopefully the shell materials are ones that cost less energy to reuse versus that of just plain gathering it fresh.

tahanson43206 · 2021-01-23 21:54:23

For SpaceNut re #36

Thanks for picking up on the scenario we are working here ...

The materials used in the carrier would be needed for on site projects, so would be immediately retrieved and put to use.

An example from history on Earth (which might have happened for all I know) would have been if sailing ships heading out from England were designed to be disassembled and made into log cabins for the settlers.

(th)

tahanson43206 · 2021-01-24 12:24:23

The idea of Void, to deliver useful materials to Mars for input to manufacturing processes, depends upon the capability of recovering those materials after they have been captured by the destination body.

Megatons of metals and other materials have been delivered to the surface of the Earth over centuries of human experimentation with ballistic transport methods of various kinds.

I looked for, and with Google's help, found an example of recovery of some of those megatons:

https://response.restoration.noaa.gov/a … dlife.html

A similar transformation has occurred at a landfill on the base's Site 36. This landfill, most likely originally part of Chickamuxen Creek and a nearby wetland, was used from 1972 to 1974 and has been inactive since that time. The fill material dumped into the creek was believed to contain metal casings from mines, bombs, and torpedoes—not exactly normal working conditions. Cleanup focused on removing scrap metal and potential munitions items from the surface of the landfill and the shoreline. The multi-agency team hauled away more than 57,000 pounds of metal and other materials from the site, with much of it recycled rather than left under the existing soil cover.

In the case of Phobos, if my guesses about the velocity of impact, and the nature of Phobos as a (possible) rubble pile, are correct, then Phobos would be potential site for delivery of many tons of valuable metals (and potentially other solid materials).

The future settlers of Mars are going to be in need of great quantities of highly refined metals and other materials presently found only on Earth. There would certainly appear to be a substantial business opportunity for an organization looking to fill that niche.

This business will be competing with those who would deliver supplies to the surface after direct flight from Earth. My guess is that the impact delivery business will be more profitable than the direct delivery competitors.

(th)

tahanson43206 · 2021-01-25 07:09:46

The potential of creating a viable business plan for delivery of bulk supplies to Phobos using impact capture is looking increasingly attractive.

A way of quickly retrieving arriving packages is to attach a trailing line to the package. This line might be given a boost away from Phobos just as the package begins to engage with the rubble pile (I'm hoping) is present to (somewhat gently) absorb kinetic energy from the package.

As a reminder, the scenario is to deliver the package to Phobos while it is receding in it's path around Mars. Ideally, no velocity adjustment at all will be required to prepare the package for impact.

Ideally, the line attached to the stern of the delivery package will remain outside the impact location, and available for immediate retrieval by an automated package retrieval rover.

If all goes well, it will turn out that goods such as grain (seeds) and similar bulk commodities can be safely delivered to Phobos using this method.

The companion business is a robust Phobos-Mars transport service, supported by fuel and oxidizer manufacturing facilities on Mars itself.

The outlines of such a capability have been discussed in considerable detail in this forum in past years (See GW Johnson et al).

A major benefit of the proposed package delivery system is the slow but steady increase in momentum of Phobos, which is otherwise due to break apart as it approaches Mars due to gravitational dragging effects.

(th)

Calliban · 2021-01-25 07:20:09

Regarding Phobos as a delivery site: if impact velocity is 7.5kms, as you have suggested, then the energy of the projectile on impact will be 28MJ/kg. If it is made from solid steel, it will take less than 1MJ/kg converted into heat by friction to melt the impactor. And ultimately, all of the energy carried by the projectile will be converted into heat on impact. At 7.5kms, your projectile is likely to dissociate along with a great deal of surface material. This will all be ejected into space due to reflected momentum.

Unless you can slow the projectile down sufficiently to ensure that it does not melt and that surface material retains enough cohesion to arrest the momentum of the projectile, you will lose most of the mass of the projectile and create an orbital debris hazard.

Last edited by Calliban (2021-01-25 07:22:33)

tahanson43206 · 2021-01-25 08:31:10

For Calliban re #40

Thank you for picking up on this topic ... The velocity of 7.5 Kms comes from SpaceX (via SpaceNut) as their expected velocity when entering the atmosphere of Mars. GW Johnson has confirmed (see posts earlier in the forum) that when Phobos is receding from the arriving vehicle, the relative velocity will be reduced by the velocity of Phobos in its path around Mars. In addition, while Phobos has some gravity, the amount is small, so the arriving package will not experience a significant acceleration (as compared to Mars).

The gravity of Mars, meanwhile, is present, and it must be taken into account, but it is off 90 degrees to the side in the activity we are discussing.

All of the velocities are worked out in detail earlier in the forum.

Your point about how the energy will be dissipated seems right to a point .... heat will definitely occur, but ultimately that heat will be distributed to Phobos as a contribution to its momentum, and thus to preserving its place in orbit around Mars.

Your point about disturbance of the surface material is well taken and much appreciated. For that I've been thinking about a retaining fabric of some kind, suitable for the purpose. The ideal situation would be for the arriving package to pass through a target opening in the fabric, suitably highlighted in the EM spectrum with either a small transmitter or a reflective surface for the oncoming package to use for orientation.

The velocity I have in mind for the arriving package is on the order of 2 kms, but I'll have to go back to the earlier posts to be sure.

This forum could certainly use a fixed repository of knowledge.

RobertDyck in particular has to keep repeating his recommendations for the Large Ship because the forum operates in a flow-under-the-bridge mode, and without easy anchors to find data, it takes significant effort (and skills such as SpaceNut shows so often) to find them.

Edit#1: I have tried to build a simple indexing capability for this otherwise amorphous forum ...

The message at the link (to be provided) here is part of a topic:

http://newmars.com/forums/viewtopic.php … 16#p162216

Solving Mars mission docking with Phobos

GW Johnson was kind enough to provide a number of details to round out the topic

(th)

Calliban · 2021-01-25 14:18:25

A quick calculation using the equation provided by Wiki, reveals that at Phobos altitude above Mars, the local Martian escape velocity is ~2.8km/s. Even if the projectile arrives at Mars with zero net velocity, it would have at least this much velocity relative to the orbit of Phobos. However, it is noteworthy that Phobos orbital speed around Mars is ~2.14km/s. If the projectile approaches Phobos on its trailing side, maybe there are scenarios where impact speeds do not greatly exceed 1km/s. It requires precise timing and manoeuvering.

Deimos might be a better bet. It's orbital speed is lower and it is further outside of the Martian gravity well. Maybe we could attach some kind of tether to catch passing projectiles?

Last edited by Calliban (2021-01-25 14:20:07)

Oldfart1939 · 2021-01-25 14:24:16

After giving this proposal considerable thought, I am going on the record as being against impacting high velocity loads on Phobos. This will undoubtedly displace a lot of the regolith and rocks at escape velocities, making a debris cloud around the moon that we certainly DON'T want or need for manned flights. This is the argument made against landing large rockets directly on our moon, that the displaced debris will have damaging effects.

GW Johnson · 2021-01-25 15:09:53

I second Oldfart1939's motion. The escape velocity from Phobos is only 28 m/s. Any impact will create orbital debris about Mars at the distance of Phobos. Pretty much a ring about Mars.

GW

Calliban · 2021-01-25 15:27:31

I don't quite understand the reasoning behind not wanting to use the Martian atmosphere to slow down. I appreciate that a soft landing of massive objects is complicated and fuel intensive on Mars. But a fairly dumb heat shield, let's say a sphere of steel coated in a refractory, should be easy enough to build. Remember, we do not need the complex systems necessary for soft landing. If robust projectiles hit the surface of Mars at 1000mph, that may be good enough if we are delivering bulk materials. But the projectile needs to be moving slowly enough that it remains nominally intact (albeit distorted) after impact.

I would suggest the minimum cost design would be a cannon ball inside a larger steel sphere, which is coated in a high temperature refractory like aluminium or titanium oxide.

SpaceNut · 2021-01-25 16:35:18

The phobos plan included gravity capture, heatshield dives to slow the speed of the ship, ion engines to not be going as fast from earth which can only be used for cargo and fuel for retro propulsion.

Calliban · 2021-01-25 16:43:34

One option for capturing an incoming projectile in low Mars orbit, might be a purpose built receiver that is anchored to Phobos using a restraining arm. Let's say a big spherical tank containing brine, subcooled to the point where vapour pressure is almost zero. A few seconds before impact, a door opens on the front of the tank, allowing the projectile to enter. If it is moving at approximately 5km/s, it will take 0.01 seconds to reach the middle of a 100m wide spherical tank, where it would impact the material inside. The door would be forced closed by hydrogen gas in this time. The projectile would deposit its energy in the water contained within. The tank would need strong walls to absorb the pressure surge and there would probably also need to be a surge tank. There should be no net loss of material. The projectile itself would probably be torn to pieces. But after a few thousand such impacts, we could drain the brine into the surge tank by gently rotating the tank on its arm. We would then collect the fragments.

Last edited by Calliban (2021-01-25 16:47:10)

tahanson43206 · 2021-01-25 18:48:07

Thanks to everyone who participated in advancing this topic!

I have scanned the posts that arrived today, and plan to return to study them carefully.

In the mean time, here is a quote from GW Johnson in the topic about Docking with Phobos:

http://newmars.com/forums/viewtopic.php … 12#p176212

The numbers are 1.9 km/s to land on Phobos from Hohmann, and 4.1 km/s to land on Phobos from the faster 2-year-abort trajectory. That's what Figure 16 shows, in the top right block of data. chrome_debug.log

The value shown is close to the value shown by Calliban in a recent post.

In his lengthy post in the Phobos Docking topic, GW Johnson asserted that there is NO orbit that can deliver a better match for delivery of bulk materials to Phobos than Hohmann. I think it is time (for me at least) to accept that and go with the result.

In scanning the posts today, I noted OldFart1939's observation that a collision (of any magnitude) with Phobos would produce unacceptable levels of debris. The example from the recent visit to an asteroid (by either the Japanese or the US) is instructive ... One of the reports I read about those visits was about the spontaneous ejection of material from the surface caused (here I'm stretching for the memory) (?possibly) solar heating effects.

In any case, the issue immediately at hand is... how can I salvage Void's Ballistic Delivery idea, given the authoritative minimum velocity difference of (about) 2 kms upon arrival at Phobos under the very best possible circumstances?

Everyone please keep in mind that Void's idea was about delivery of bulk supplies and NOT about people.

I think the answer is to use an ion engine (or a relative if there is something different that will work) to smooth out the flight so that a soft landing at Phobos can be achieved.

We are talking about bulk deliveries of:

1) Seeds such as wheat (for use as flour if not for planting)
2) Concrete mix to build structures on Mars immediately after landing
3) Water for supply of all kinds ... human needs, construction, fuel, ...
4) Steel and other metals
5) Wood/plastic/other products for immediate use by settlers in configuring their habitats
6) Fabricated parts for machines, packed in preservative (I'm thinking here of World War II gunk around metal parts)

There should be (and I'm reasonably confident) ** will ** be many Earth based companies who will want to be part of the Mars Package Delivery industry.

I will go back over today's posts to be sure I've absorbed as much as I can, but in any case, thanks to everyone for helping to move this idea of Void forward.

Void's ideas are (by definition) impossible for ordinary persons to come up with, so if most of them don't work in the real world, that's the price we pay for the few gems that show up.

I think this one is one of those gems.

(th)

SpaceNut · 2021-01-25 19:49:00

There are parts of the page of equations which still applies even when starting a near zero speed the motion is the draw of gravity plus the little push to get it on its way. That force is still a mass equation with gravity causing it to go faster towards the eventual end on the mars surface. The force can be determined if you know the angle of attack, mass total going to the surface. Heating lose of materials in the upper atmosphere should be by far less and not requiring a heat shield. What matter is the broad face diameter that the thickening air can push against to slow the materials as much as possible. Since the mass will be mostly intact as it strike the surface its up to how robust the out shell is as to whether we will have spilt wheat all over the surface or a bursting into flame wreckage.

GW Johnson · 2021-01-25 19:51:00

Calliban's idea in his post 47 of the catch tank full of sub-cooled brine requires doors of dimension near 50 m that can be closed during the impact time of something like 10 msec. Failure to achieve this means brine will be splashed out of the tank as both liquid and vapor, at a velocity comparable to the impact velocity, which in his post was 5 km/s, and in my estimate is never less than 1.9 km/s, even from min-energy Hohmann transfer. The escape velocity from Phobos is about 28 m/s = 0.028 km/s, so this debris is ejected into a ring about Mars at the distance of Phobos, and is made up of (hard) ice particles. Which is why I said what I said in post 44 above.

How do you move a door that big that fast through something like a 90 degree angle? Handwaving about "hydrogen" is not an answer. My concern is that the stress applied to a door that size exceeds the stress capability of all known materials from which such a door could be constructed. I have not analyzed this case, but my engineering intuition says this cannot be done.

As for using aerobraking in Mars's atmosphere to slow the package down (Calliban post 45), yes, that is theoretically possible, but in reality you have to take into account the observed fact that the density of Mars's upper atmosphere varies erratically by a factor of 2, changing the drag effect you can get by that same erratic factor of 2. That variability puts hitting your target on Phobos completely out of reach. That atmospheric variability is not my claim, but the claim of the recognized authorities on the subject: Justus and Braun. Perhaps after there is a network of GPS and weather satellites around Mars those density-variation difficulties can be overcome, but such does NOT exist now. Nor are there any real plans to bring it into existence anytime in the foreseeable future.

As for using a ceramic like aluminum oxide as your heat shield for aerobraking, you need a way to dye that material black for an emissivity exceeding 80%, or it will overheat before it can reradiate enough energy. As it naturally is, that material (and most other oxide ceramics) are a brilliant white in color, with emissivity in the infeasible range for effective re-radiative heat shield operation, under 20%. Anybody know how to introduce carbon black into a ceramic melt without said carbon catching fire before you can mix it in? I certainly do not.

Plus, if your ceramic is not low density (and plain aluminum oxide is high density), you will have enormous thermal conduction to your substrate, precisely because high density is synonymous with high thermal conductivity, in every solid (or liquid) material known to man. I know how to blacken the surface of a ceramic composite after I lay it up, but not how to blacken a ceramic melt. If you are talking low-density ceramic composite, you are talking about something resembling space shuttle heat shield tiles. Not cheap or easy to do.

GW

Last edited by GW Johnson (2021-01-25 19:56:06)

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