Ballistic Delivery of Supplies to Mars: Lithobraking

Void · 2023-10-05 09:34:01

I may suggest that landing on sand is a reasonable idea, but you might land on Korolev Crater, which of course is not the Equator.

If some of the materials are to evaporate on impact then that can be water ice, perhaps. And if you have an inflatable heat shield, then perhaps that can also be a cushion and sacrifice materials.

And it may be true that visually debris from the impact will be rather visible, if not under the ice, and perhaps also indeed a tracker might help, and metal detectors on the ground, and perhaps sonar.

You also do have the seasonal dry ice caps to do a similar thing perhaps. South Hellas might be good for that, I think, at the greatest extent of Dry Ice, and as you have almost double the average air pressure there. Well, I think that the southern winter deposits CO2 in the south half of the Hellas Depression, but I cannot find images or maps for that. The thicker air should make your chances better for a surviving payload, and also, I believe that there are sand dunes in the depression as well. They may be soft or icy, I think.

Dunes: https://www.jpl.nasa.gov/images/pia2570 … -in-hellas

As for landing on CO2 ice caps, the spider process may make them more shock absorbing in the spring, I think.
Spiders from Mars: DB: https://www.livescience.com/spiders-on- … y-ice.html

Punky partially sublimated Dry Ice with VOIDS in them perhaps.

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

If your loads are actually carried to Martian orbit by electric propulsion, then also your timing can be better facilitated, and your entry speed can be slower. But that partially removes the notion of ballistic, but should we care? I think interplanetary entry speed if given a value of 6.5 is relative to 4.0 from orbit, but that is just my very fuzzy math. 6.5 to 4.0 ratio?

Done.

Last edited by Void (2023-10-05 10:09:06)

GW Johnson · 2023-10-05 10:29:08

Allow me to clarify what I posted in post 298 above.

One of the options was to stay under a ballistic coefficient of 100 kg/sq.m. That was to come out of hypersonics high enough (20 + km altitude) to enable deployment of a ringsail chute, which gets you down to at, or just barely under, Mach 1 at impact.

If you hit at Mach 3-ish without the chute, you will create a crater, and the cargo will be shattered to tiny bits and widely scattered, NO MATTER WHAT SORT OF CONTAINER IT MIGHT BE IN! The container will be destroyed, too! And THAT outcome is what is being ignored in this discussion.

But if you use the chute and strike at only Mach 1 or just-subsonic (about 220 m/s on Mars), there will still be a recognizable wreck, and if your container is stout enough, it will survive, and the cargo inside will not be scattered. That is comparable to most aircraft crashes here on Earth (under or well under about 330 m/s), and the wreckage scene will resemble one of those. If your cargo is packaged securely like a flight data recorder, it can be recovered more-or-less intact.

If you go heavier than about 100-200 kg/sq.m ballistic, you will come out of hypersonics at local Mach 3 (about 0.7 km/s) at a much lower altitude (1-10 km), seconds from impact. Your only option is massive rocket braking to get the speed down under Mach 1 at impact. That scenario is little different from massive rocket braking for a soft landing, so it is less attractive than the Mach 1 chute crash scenario.

As for the chute scenario at low ballistic coefficient, the difference between it and a soft landing is massive rocket braking. Terminal velocity for chutes on Mars in that thin atmosphere are transonic, quite unlike what happens on Earth. What you are familiar with here simply does not apply there.

So, if you delete the last-second rocket braking, you have the Mach 1 chute crash. If you add the rocket braking, you get a soft landing. The rest of the entry sequence looks just like all the lander probes sent to Mars so far: they all use chutes.

If you fail to use the chute, you strike at 3 times higher speed, roughly 10 times the kinetic energy. No materials withstand energies that large! Your cargo AND its container get pulverized and scattered widely! The same happens here at similar energies. That experience applies everywhere, and is independent of the atmospheric density.

As to the question of entering from orbit or off the interplanetary trajectory, it makes no real difference! The initial entry speed is dissipated by entry hypersonic drag, either way. The higher entry speed merely requires tighter control over the shallow entry angle required, limited only by the risk of "bouncing off the atmosphere".

What governs survivability is the speed and altitude at the end of hypersonics: the local Mach 3 point, just after the peak deceleration and peak heating points (no, they are not the same!). That end-of-hypersonics speed is still too fast for anything to survive the crash intact, so you still have to slow down by another factor of 3! There is NO WAY around that requirement! Which is also not being faced in this discussion.

You have to be high enough at the Mach 3 point to do that; the practical solution being a ringsail chute, as demonstrated for some decades now with landers on Mars. And THAT (the need to be high enough for a chute to deploy AND decelerate you) is what limits your ballistic coefficient to under 100 kg/sq.m on Mars. That is quite unlike what happens in Earth entries: Mach 3 point altitudes are above 40 km here.

Otherwise, if you don't use the chute crash approach with its ballistic coefficient limit, you are faced with adding massive rocket braking. And if you do that, you might as well go for the soft landing.

If you don't believe me, go consult somebody who deals in kinetic energy weapons. Or somebody experienced with investigating military aircraft crashes. Either will tell you the difference between damages for 220-330 m/s versus 700 to 1000 m/s is quite dramatic. Beyond a certain applied energy, all atoms/molecules fly apart from each other. There are no magic materials that resist such abuse.

GW

Last edited by GW Johnson (2023-10-05 10:54:46)

GW Johnson · 2023-10-05 10:59:27

There is also the form of the heat shield. The need for a backshell depends upon whether your containerized cargo can withstand getting its surface red hot or not. If it can, all you need is a windward heat shield, and your containerized cargo can ride exposed atop it. If it cannot, then you must have a backshell to protect the containerized cargo from wake zone aeroheating by incandescent plasma.

Exposed, the energy balance is aeroheating input balanced by hot-surface re-radiation as the output. The hot surface temperatures to make that feasible are in the 1000-2000 F range.

Either way, the ringsail chute package has to be protected from the heating.

GW

Last edited by GW Johnson (2023-10-05 11:00:31)

kbd512 · 2023-10-05 11:12:38

GW,

If 2,000F is the max temp, that means a reasonably thin and light ceramic fabric (Nextel - 2,372F max continuous service temp) and aerogel foam sandwich core backshell should do the trick.

Void · 2023-10-05 11:33:21

Please keep in mind I have strong respect for each of you in this topic. I am sort of here to learn.

Terminal Velocity claimed for Starship on Mars: https://space.stackexchange.com/questio … x-starship Quote:

The terminal velocity of Starship on Mars is approximately 4.8 times faster than on Earth1. The only mention of terminal velocity on Mars for Starship was on a blog post, which stated 66-68 m/s for SN8, implying ± 320 m/s on Mars2. The SpaceX Mars landing simulation has a ~40 s landing burn initiating at ~Mach 2.3 = ~550 m/s (about 1.7 g Earth) for a total velocity change of ~700 m/s3.

I am still trying to reacquire the numbers for that.

So anyway, I thought the speed was not too outrageous. But the amount of empty volume in the device needs to be at least as much as a Starship landing on Mars, I presume. And then it might be more. So, then if you have a material that is valuable in itself for the shell, such as an alloy or plastic, it might not be totally unthinkable. At least for now for me.

Done

I don't like the 320 m/s as it has +/- in front of it. If is a useful number, then:

An online converter said Mach 0.93294461

But I am way out of my area of competency, if I even have one. But that is for Starship, and I presume that is with a full cargo load.

As I have said if you have a shell that is of a useful material, then maybe you can make those numbers better.

If you need to slap me up about this then go ahead, I will accept that I did put my head into the lions mouth myself.

If you can make the shell large enough and the shell is of a valuable material, then you might also have a payload of items that Calliban mentioned such as Oatmeal, Powdered Milk, or special metal alloys.

I also mention that in the cold of the Martian spring, not only will the air pressure be high at the bottom of the Hellas Depression, but the air should be more dense than in summer.

So, terminal velocity would be affected by that as well.

If we assume that the aeroshell will pop and crumple, then we might hope to dissipate some energy that way on impact.

Keep in mind that I am only trying to define what is true, I am not going to support what is discovered to be unobtainable.

Done

Last edited by Void (2023-10-05 11:52:54)

GW Johnson · 2023-10-05 12:29:15

Kbd512:

The 1000-2000 F temperature is the range at which something with a high thermal emissivity can re-radiate significant energy per unit time from a hot surface. This was used as the re-radiating black (or very dark) aft metal surfaces of the Mercury and Gemini capsules.

They could not do that on Apollo, the near-escape entry coming back from the moon added huge plasma radiation heating to the already-huge convective heating. It was too much for an otherwise-insulated metal to equilibriate, re-radiating at survivable temperature. So Apollo's backside was coated with ablative, just a thinner layer than the big blunt, thick windward-side heat shield. One problem with counting on re-radiation at ever-higher entry speeds is that the plasma sheath becomes opaque to infrared as its optical glow becomes opaque. Re-radiation cooling is no longer feasible at such speeds. The emitted radiation cannot penetrate the plasma sheath. It just comes right back at you.

At Earth, the sheath radiation usually starts to dominate over convection at about 10 km/s speeds, and presumably elsewhere, as well. Apollo's return from the moon was at 10.9 km/s, escape is about 11.2 km/s, and fast returns from Mars fall in the 12-17 km/s range. Return from low Earth orbit is only about 8 km/s.

The effective driving temperatures for convective heat transfer to the surface of the vehicle can be crudely estimated as deg K = speed in m/s. At 8 km/s, that’s 8000 K. Etc. Very crude estimate, but in the ballpark. Entry engineers have been using that approximation since about 1953. You definitely want to equilibriate well below temperatures like that!

There's some re-radiation cooling coming from the charring surface of an ablative, which is often nearer the fully-charred temperature of the material than any sort of re-radiation-moderated heat flow equilibrium point. But the main aeroheat input goes into the energy required to char the material, and while some heat conducts inward through it, the majority is carried downstream by the char gases and eroded particles as the surface recedes. Solid rocket and ramjet ablative liners also work that same way.

Actually, I agree that the Nextel fabric plus some low-density insulation would serve well as a backshell for Mars entry. Even direct off a fast interplanetary trajectory, speeds are under 8 km/s at Mars, unlike at Earth. Entry from low Mars orbit is only about 3.6 km/s. Even Mars escape is only 5 km/s.

The ceramic surface will get hot enough to re-radiate significantly, and the low density of the insulating layer underneath acts to sharply reduce thermal conduction inward. If the aeroheating applied is high enough (as on the windward side), the surface usually needs to have a high thermal emissivity to survive heating up to a re-radiation balance temperature. With lower wake-zone heating, even the low-emissivity white surface typical of ceramics is adequate to achieve a survivable balance. That’s why the windward surfaces were black, and the leeward surfaces were white, on the space shuttle. They needed the white backside for on-orbit solar temperature control, and that same white surface could survive entry from orbit. Same applies to X-37B.

Void:

The terminal velocity for Starship was reported to be just under 70 m/s, when falling broadside low in the atmosphere where the air is dense. Up high (around 30-40 km) earlier in the Earth-entry sequence they want to fly, the air is very thin, and the broadside terminal velocity is transonic to low supersonic. They are doing the "belly-flop broadside descent" after the hypersonics are over, to slow down to very low speeds as the ground gets close, and thereby reduce the rocket power to land.

None of that applies at Mars, because they cannot use the "belly-flop trajectory" there at all! They come out of hypersonics at or below 5 km altitude, moving about 0.7 km/s (local Mach 3), and roughly oriented 45 degrees down. They plan to pull-up aerodynamically to about 10 km, reducing speed to about local Mach 1 or just above, or about 0.2-0.25 km/s. From that local pull-up apogee, they quickly pitch to tail-first, and power to a landing. Personally, I think they will need the rocket power earlier, assisting high-supersonic lift to actually make the pull-up maneuver successfully. The warmer the day, and the higher the elevation, the larger the probability that the pull-up requires thrust to help it.

GW

kbd512 · 2023-10-05 12:50:01

Void,

I assume the basis of the underlying question is, "How much is my fuel bill and how much cargo can I realistically carry?"

I think the answer to that is determined before we arrive at the reentry interface for Mars.

The reentry velocity, and especially the pressure variability of the Martian atmosphere combined with variable reentry velocity, is why you get such a wide Vmin / Vmax range for terminal velocity, plus the degree of optimization of the aerobraking maneuver (coefficient of lift generated by your heat shield / "surf board" for hypersonic-to-supersonic surfing). Where you land above or below MSL must also be factored in. I think you already noted most of this. It's a large uncertainty range because the factors involved dictate significant differences in retro-propulsion engine burn times.

I question sending a valuable Starship all the way to Mars. I think it's nuts, but I'm not Elon Musk. Use Starship to put the payload in a halo orbit around Earth, Starship returns to Earth for immediate reuse, and one last push using storable chemical propellants in a "cruise stage" completes the TMI maneuver. JPL's "Sky Crane" method works quite well and happens to be pretty close to the minimum mass option, with the lowest being propulsion built into the lander. We would skip parachutes entirely, use aerobraking only, and then go straight to retro-propulsive landings. GW and I went back and forth on this for a long time, but eventually I came around to the idea that a parachute was not practical for a very large payload.

Void · 2023-10-05 18:15:41

I am willing to agree, however for fun, it sometimes is compulsive to see where the limits are, and why.

I might wonder to modify, your plan to use electric to finish the path to Mars, and with that possibly at times the use of Ballistic Capture.

An entry from Mars orbit would be less challenging.

In the system, I would also opt for CO & O2 Mars ships, for both suborbital and orbital access if possible. In that case those could go up and get relatively "Dumb" loads and bring them down.

As for Suborbital CO & O2, not every base on Mars will have everything so those could move stuff about, and in some cases drop things from an altitude perhaps. As Mars has a atmosphere there is a terminal velocity of that sort. So, for fun I imagine a sphere of thin Stainless steel.
If the weight to air drag were favorable maybe it would work. I expect it to pop and crumple though.

But of course, it is unlikely that a base would need such a delivery, but it is a thought puzzle of sorts. If you could not do that then it seems unlikely that you could do something harder. But in the case I am referencing the ship would not need a heat shield (I hope), and the ship might circle entirely around Mars dropping it's load on the way and then land back at it's base or an alternate suitable base.

As I see it Nuclear Reactors could cook up the CO and O2, without the need for heavy equipment to secure an ore, (Water Ice), and these could be almost anywhere. And yes if needed for you drop you might use some of the methods that you and GW discussed rather than simply dropping a "Dumb Load" and hoping for the best.

I am guessing that water for bases might not be too much of a problem as recycling is at least 98% (ISS), and the soils seem to have water that can be extracted for a price. And imports with Callibans "Covered Wagons" might not be out of the question.

For water wells would be the best, I think but the Ice Slabs are an option that has been discussed.

Ballistic Capture gives us a chance to figure out what the minimum requirements are for some material deliveries, and then if that isn't good enough then you have to add additional features and methods.

Done

Last edited by Void (2023-10-05 18:28:47)

SpaceNut · 2023-10-05 19:05:21

The entry equation is not just the angle but the starting velocity - air braking (which is related to the diameter of the heat shield} + with the line of tangent time for impact.....

One earth a large iron core is about all that and a few rocky stone types are all that remain from there ballistic impact to un prepare surface.

kbd512 · 2023-10-06 04:39:30

Void,

I think the real question is whether or not you would have a payload mass fraction advantage from using electric propulsion to stop in LMO first. I advocated for stopping in LMO (3.6km/s or Mach 10.6) when the payload includes a crew because a lower reentry velocity confers advantages specifically applicable to humans. They pull fewer gees upon reentry. That remains a real concern. Aerobraking from LMO velocity buys more time to bleed speed using less extreme gee forces to do it. Creating a situation where your crew passes out during a critical phase of flight is, at least to my way of thinking, highly undesirable. If we have the tech to capture into LMO for crewed missions, precluding that possibility by roughly halving reentry velocity, then we should use it.

For cargo missions, I think you need at least 5,000s and probably more like 10,000s, before there's enough of a mass advantage over a slightly better heat shield, which is mostly fabric based. My advocating for electric propulsion for cargo was mostly about getting to Mars using a much lower propellant mass fraction. The retro-propulsion mass fraction is quite low. The ability to propulsively capture into LMO could be desirable because there's at least the possibility of repositioning the cargo for the reentry maneuver if trajectory calculations are slightly off, but JPL has thoroughly proven their ability to precisely hit the desired landing target without it. Each successive robotic mission has been more precise than the last.

For cargo missions, I think direct entry remains our best option. If we have suitable propulsion hardware for removing more reentry velocity while using significantly less mass than a more robust heat shield, then we should at least consider it. All cargo is likely to remain well within gee limits, but if we can demonstrate clearly definable mass and cost advantages to using propulsive-all-the-way flight control, then it's worth the added complexity.

As far as surface transport is concerned, I think nuclear powered rovers are our best option. I advocated for using a nuclear powered M113 facsimile rovers because they can provide radiation protection and global range. If nuclear-electric is too expensive, then CO-fueled SOXE fuel cells or sCO2 gas turbines can still provide substantial range.

As far as returning to Earth from the surface of Mars, I agree that CO / O2 (around 300s Isp in a vacuum) offers a significant complexity advantage, despite its pedestrian Isp. I differ from Dr Zubrin on the practicality of his NIMF concept. I think the reactor should remain on the surface of Mars, with the Earth Return Vehicle powered by conventional pump-fed chemical rocket engines. If we have nuclear-electric rovers, and nuclear reactors for primary power, then the rovers can lug the CO / O2 propellant tanks around on the surface. Here on Earth, we use motor vehicles to transport fuels overland. Aircraft-delivered fuel is only used when no other more practical option exists. The novelty of having the fuel refinery aboard the aircraft is offset by the operational challenges associated with actually using it.

Carbon Monoxide can also be used for:
1. fuel source for SOXE (solid oxide electrolysis) fuel cells to supply emergency backup electrical power
2. fuel source for sCO2 gas turbine engines for heavy equipment
3. Cutting torches or heat sources (flame temps: O2 / CO - 5,336°F; O2 / Acetylene at 5,600°F)
4. Steel-making

Why both SOXE and sCO2 gas turbines?

Both get very hot in operation, so no real advantages there, either way.

The fuel cell is about 80% efficient, but 3kW/kg and 3kW/L. A 3-stage sCO2 gas turbine can be around 60% efficient, but 10kW/kg to 20kW/kg. A 250kW sCO2 gas turbine wheel is the same size as a quarter, or the size of a soda can after you include the turbine housing / casing. A fuel cell is much larger, about 83L in volume for the cell itself, or about the same size two beer kegs with pump accessories. Both operate at similar temperatures. Fuel cells are more suitable for backup power where weight and volume is a lot less important than fuel efficiency, whereas the other is more practical for vehicle applications where weight and volume matter greatly.

I also think obtaining water is going to be a lot harder than most people imagine it will be, so most of it will be devoted to human consumption.

Void · 2023-10-06 06:14:04

Well, we have convergence on CO & O2 to a large degree.

But where I differ on the idea of direct to Mars, is that Starships are put out of service during the duration of flight to Mars, and back to Earth, when they could be doing so much useful work in that time. Electric passage from Earth to Mars helps solve that for many parts of Cargo. Most mass travel is going to be Earth>Mars. Having a ship that jumps up and down Mars Surface <> Mars Orbit, reduces the rocket equation pyramid height. Electric being efficient, also would not have to carry the landing propellants, or the tanks to hold those propellants. To me CO & O2 for the Mars Surface <> Mars Orbit makes sense, as CO2 is more universally available on the surface in bulk than is water. Water seems like it will be local and lumpy in its abundance.

Trying to get closer to the core of this topic, I have mentioned elsewhere methods to eject payload in the near landing process to ease the load on a landing ship. We have at least 4 situations where payload might leave the ship prior to landing. First being most faithful to this topic, Earth > Mars, then Mars orbit > Entry with heatshield and atmospheric braking from orbit, then Mars Orbit > Ship assisted atmospheric entry with a drop prior to landing, then sub-orbital > drop from the ship prior to landing.

I don't see any reason not to contemplate each of these, but not necessarily practice them all with the same emphasis. The easiest might be to have a sub-orbital ship, with cargo drop as dangle or just drop moments before landing. And of course that is only suitable for some types of cargo.

I agree that wheeled vehicles may well have their value as the main method of moving heavy cargo, but as on Earth there could be exceptions where some materials might be moved by "Air".

Raw materials will likely be scattered across Mars and also be seasonal, so wheeled and air transport, (Sub-Orbital), are probably going to be useful.

But if it can be arranged to push a load to Mars and slam it on the ground, and have some material delivered in a usable form, then by all means make that work.

I liked Callibans materials from post #299 quite a lot:

Calliban
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From: Northern England, UK
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GW Johnson wrote:
Those physics pretty much leave you with two, and only two, options for crashing cargo onto Mars with any practical hope of recovery. (1) reduce the ballistic coefficient below about 100 kg/sq.m, which limits your entry mass (cargo plus heat shield) to a mere fraction of a ton. (2) add some retropropulsion to it, to reduce its speed below Mach 1 before you hit. That can be quite difficult to do with the heat shield in the way, with only a single handful of seconds to impact if you fail.
GW
The value of the lithobraking idea rests upon its ability to deliver low value commodity products (things like industrial metals, oatmeal, powdered milk, etc) without the need for any active propulsion, guidance or landing systems, except for a dumb heat shield. We send a ship on a free return trajectory and release the cargo a few days before closest approach. The ship would return to Earth, the cargo would hit the Martian atmosphere. I think a ballistic coefficient of 100kg/m2 is acceptable. The materials delivered would be packed into steel shells representing about half of total projectile mass. The heat shield would be a sphere that would inflate around the shell. We might even use water as the inflating agent, allowing it to boil into steam from the heat flux of entry. A total payload of 100 tonnes, could be divided between a couple of thousand spherical projectiles.
The main difficulty I can see is retrieving these payloads from the surface. There are electronics that can be built into shells that would allow individual payloads to be tracked. But if we release a cluster of payloads at the top of the atmosphere, they could disperse over an area of hundreds of square miles by the time they hit the surface. A lot of EVA activity would be needed to collect them up on the surface of Mars. The best option I can see is to divide payloads into small units and hit the atmosphere dead on rather than at an angle. Individual spherical packages would be wired together, so that they make it some way into the atmosphere before atmospheric friction destroys the wires. If we time the deliveries to consistently impact the same area on Mars, we can establish a small base whose dedicated function is to go around collecting the projectiles. Likely we want to pick an area close to the equator, with deep accumulations of loose sand.
Last edited by Calliban (Yesterday 09:55:25)

But of course, I prefer Hellas in the cold, as that is the maximum pressure and density of the atmosphere that is likely available.

Done

Last edited by Void (2023-10-06 06:31:30)

GW Johnson · 2023-10-06 08:48:46

Just for perspective, most (but not all) of the lander probes snt to Mars were "ballistic capture" direct from the interplanetary trajectory. The exceptions were released from orbiters.

The free entry probes simply get in the way of the approaching planet, which "runs over the spacecraft" essentially from behind. This is done with a geometry such that the potential impact is essentially a graze, at a very shallow angle to local horizontal. Speed at entry interface varies from 5.4 km/s to about 7.5 km/s. (It's only 3.6 km/s from low orbit.) Angle is about 2 degrees below local horizontal, and that needs to be maintained through peak gees and peak heating.

Early in the entry, you have to worry about bouncing off the atmosphere (like skipping a stone on a pond or lake), so hypersonic downlift capability helps with that. Later in the trajectory, you want to decrease the gravitational "droop", so that your trajectory angle doesn't get too steep. Hypersonic uplift capability helps with that.

Up to about 100 kg/sq.m ballistic coefficient, the altitude at which you come out of the hypersonics at local Mach 3 is above 20 km. You ditch the backshell, then pop a drogue, then ditch the heat shield. By that time (only seconds later) you are nearer 10 km altitude, moving about Mach 2.5, and can (most likely) successfully deploy a ringsail chute. That is what slows you down to near Mach 1 (about 0.2-0.24 km/s). It has time to decelerate you, if your end of hypersonics altitude is above 20 km. If not, you smack the surface.

Some sort of rocket braking is required at the last second or so, to slow you to a survivable soft landing, if you are a probe like the ones we have sent. The closer you are to 100 kg/sq.m, the more difficult this is to implement. The two 1 ton rovers were right on the hairy edge of chute feasibility, and required the skycrane braking system to do the braking at minimum equipment weight.

The "lithobraking" idea dispenses with the soft landing rocket braking stuff. But you still need the heat shielding and the chute, and you have to stay well under 100 kg/sq.m ballistic coefficient to make it work reliably with simple designs. You cannot dispense with the chute, because nothing will survive in a recoverable form, if you smack the surface at 0.7 km/s (local Mach 3). It could be hardened to survive, in recognizable wreckage, if you only smack the surface at 0.22 km/s (local Mach 1), which is an order of magnitude less kinetic energy to deal with. Mechanics of materials (all materials!!) at extreme energies dictates that final slowing to local Mach 1.

GW

Last edited by GW Johnson (2023-10-06 08:53:45)

Void · 2023-10-06 09:29:19

Well, technically, if the heat shield, back-shell, and parachute can be recovered and repurposed, then it could be considered worth the trouble. After all you delivered mass and it may be of some use.

But I think (th) does not necessarily feel warm to that in this topic, but still, good, the potential is not entirely wasted.

Done

kbd512 · 2023-10-06 09:34:19

GW,

Is there a realistic way to do enough braking with a large enough "surf board", to simply allow "dumb cargo" to smash into the ground?

I'm talking about powdered metals / plastics / ceramics for construction, powdered food stuffs like flour / sugar / dried fruits and nuts / water, or fuel tanks. Let's say we put the cargo inside a metal or plastic can, surrounded by this aerogel "surf board" that provides a low kg/m^2 value and a lot of padding to absorb the impact energy.

I assume we can design a container system to survive an impact at, say, 300mph. If we put enough foam around the payload container, can we deliver the payload that way?

tahanson43206 · 2023-10-06 10:23:40

For kbd512 re #314

Your question of GW inspires this question for me ... has anyone on Earth performed tests to determine what G forces can be sustained by delivery packages?

I would hope the answer is yes, but I don't know for sure, other than crash dummy tests that are performed to meet automobile and aircraft safety tests. Perhaps ??? some of the body design in modern vehicles includes lessons learned from such tests?

I want to deliver (or more accurately) be ** able ** to deliver, a shipment of glucose sufficient for Dr. Zubrin to refuel his methane rocket without having to fuss around with atmosphere compression. As I understand it, and pending the arrival of a ** real ** chemist on the scene, glucose contains all the atoms needed to make methane and O2 for return trip from Mars. If we can find a cost effective way to spot place that shipment on the surface, then there ought to be a market.

It seems to me that the members of this forum are edging this topic closer and closer to a viable business opportunity.

(th)

kbd512 · 2023-10-06 12:29:09

tahanson43206,

Crash energy tests are something we can calculate, but I contacted ERG Aerospace about this, because they make metal foams and do work for NASA. Maybe they'll get back to me, maybe not, who knows.

tahanson43206 · 2023-10-06 14:36:20

For kbd512 re #316

Thanks for picking up on this opportunity.

I sure hope ERG Aerospace decides to give you the courtesy of a reply.

I expect that just as Calliban calculated earlier in this topic, which (apparently) everyone forgot or never read, there is a range of options available for delivery of supplies able to travel in this way.

Crush foam can be made of carbon (I understand) as well as metal, although metal would have immediate value on Mars. It would be nicely compressed by the landing, ready to go into a smelter.

(th)

Void · 2023-10-06 14:44:16

Since you didn't ask, I have this, I call a flip ship method:

Edible structure is an old NASA concept, which I cannot now find on the internet. It likely would need prolonged soaking in water to become edible. But in some cases, could be part of the interior structure.

The object is perhaps a Stainless-Steel balloon. It needs whatever it needs to pass though the heat of atmospheric entry.
A length of chain remains in the cylinder chain pot as the opening is on top during hot entry to the atmosphere. When possible, the metal balloon flips 180 degrees, and adopts a parachute configuration as the chain falls to dangle out of the chain pot.

In this part of the flight Mars air is rammed into the metal balloon by the speed of the device. I think Starship can get up to 6 bar without popping.

Ideally as the ship slows down, compressed air is jetted out of the bottom of the metal balloon and helps to slow it.

Upon impact the chain penetrates sand, perhaps a sand dune and introduces chaos into the grains, fluidization. The compressed air emitted flows between the bottom of the ship and the dune and cushions it. Air may penetrate the dune further fluidizing it. This may cushion it more, and then you get into crumple mode where the volume of the balloon shrinks but air is still then being pushed out the bottom.

There could be variations of course, but I am short on time and have something to do.

The chain by the way could be of special alloys.

Done

Last edited by Void (2023-10-06 21:11:09)

tahanson43206 · 2023-10-06 20:20:35

For Void re #318

How far you've come, in mastery of your visual presentation!

Please look at the Blender topic to see where you may be able to go, if your energy level is up to the challenge, and your interest carries you past the inevitable early struggle.

Regarding your ship and chain idea ... Would it help to rotate the "saucer" while it deals with the heat of encounter with the atmosphere?

(th)

Void · 2023-10-06 21:09:45

Well, Rotary Rocket Blades have been considered for atmospheric travel of spacecraft even on Mars.

https://en.wikipedia.org/wiki/Rotary_Rocket. Perhaps helicopter blades on the outer perimeter of the device?

Centrifugal force possibly might modify the forces of impacting the atmosphere trying to crumple the device.

But this needs consideration. I am not sure how much of an improvement this could be.

We are likely wanting as simple of a craft as possible but the device I previously described is complex in it's way.

I do not offer it as a finished product, but as a start of a chance of something that might work.

I do have complexity in my life just now I have to schedule many medical issues. Chances are that I am rather healthy, and that my medical treatments will keep me on the up side of the grass.

Not as serious as it sounds, but prudence requires that I be completely tested out. Also, I am looking for a new car, and to move.

So, busy.

Done

Spin to assist in heat shielding, maybe can help.

A coating of Aluminum on the inside of the windward part of the shell may help as the Aluminum should melt before the Stainless Steel shell would.

But I am afraid then that Aluminum and Stainless Steel may start to alloy.

Perhaps not if the Stainless is not melted.

In the event of using that method, then melted Aluminum may collide with Edible Structure, which may not be a good thing.

So, the heat shielding on the outside of the Stainless Steel, may be thinner, if the Aluminum take some of the heat with a melt process.

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

https://www.bing.com/search?q=Melting+p … showconv=1
Quote:

Melting point of Aluminum: 660.32 °C

https://www.theworldmaterial.com/meltin … %20rows%20
Quote:

Stainless Steel Melting point (°F) Melting point (°C)
304, 304L, 304N 2550-2650 1400-1450

Done

Last edited by Void (2023-10-06 21:24:47)

tahanson43206 · 2023-10-06 22:00:26

For Void re health ... best wishes for success in navigating this phase of life! The longer you remain above the grass, the better!

I'm hoping this next question will stimulate your creative thinking...

Perhaps I just missed your explanation, but if you are willing to repeat earlier work, it would be appreciated....

The round shape you have proposed would collapse under the pressure of atmosphere, so you will have taken steps to insure it retains a sturdy shape during deceleration in the atmosphere.

As a reminder for our readers, NASA tested an inflatable heat shield using a component of the SLS system, if memory is working. My recollection is that the inflatable heat shield was cylindrical in aspect, and that it performed well. It was carried aloft and then accelerated toward the Earth to simulate a return from off-Earth.

Your circle shaped device would have the opportunity to slow the speed of the package somewhat in the thin atmosphere of Mars, if it can hold it's shape.

(th)

kbd512 · 2023-10-06 22:38:12

tahanson43206,

To my great surprise, I received a response from ERG Aerospace:

Thank you for your recent webchat inquiry below. I will be happy to assist you.
The folks working on the SHIELD program reached out to us and were evaluating foam for their design, but our aluminum foam would likely not be suitable for their use case. This might help give you a better idea on whether it’s worth considering, if the conditions are right, if that makes sense. If you have an impact scenario that you would want us to do an initial feasibility study of, please let me know more details and I will be happy to relay it our engineering team.
Fundamentally, metal foam is a good structure for this type of impact because it can be designed to crush at a predictable and relatively constant stress throughout most of its deformation.
I hope this helps and I look forward to your feedback and/or further questions.

Void · 2023-10-06 22:53:05

I don't want to cross talk against what kdb512 is presenting. But typical probes to mars enter edge on, and then go to circular cross section as they enter, so, I would anticipate the collapse on atmospheric pressure is not mandated.
http://www.ninfinger.org/models/probes/ … lls03.html
Image Quote:

So, how did the Viking aeroshell not collapse?

I have provided the notion of internal structure made of edible structure, but also other necessary methods can be included. I have also provided a possible internal thickening of the windward aeroshell portion with a coating of Aluminum on the inside. And that may cover, the aerobrake phase.

After the flip-over, the use of ram compression may pressurize the interior of the metal envelope as it decelerates into the lower atmosphere.

The pressured inflated metal envelope will resist crumple on impact but crumple on impact at the end is another way to manage the sudden change in inertia.

Sorry kdb512, I have to keep on top of these things, or all my efforts will be dismissed without proper reasons.

Done.

One desire is to keep the average density of the objects volume lower than that of the Space Shuttle or Starship, or Dragon Capsule. In that case impact with the atmosphere will be handled better as the ratio of surface area to total mass will be a better ratio.

In other words like a parachute. A parachute of the same size will brake a 1 ton weight better than it would a 2 ton weight. Or a parachute twice the size would brake a 1 ton weight twice as well as a normal parachute.

Done

Last edited by Void (2023-10-06 23:07:40)

Void · 2023-10-06 23:25:25

I have another concern which I address with respect to GW Johnson.

In a high speed aircraft impact, where nothing much is left, is the explosion only inertia, or does it involve an air fuel explosion also? That could matter.

Was the aircraft out of explosives such as fuels or even explosives?

Done

GW Johnson · 2023-10-07 08:45:55

Void:

To answer your question, most of the explosion energy is simply the almost-instantaneous conversion of kinetic energy to heat, vaporizing the aircraft and some surrounding rock. There may be chemical release from fuel or from weapons carried aboard, but that is minute in comparison to the impact kinetic energy.

There are kinetic energy weapons, which are solid slugs with no warhead. They make a huge fireball and do immense destruction, with no chemical release at all. The requirement for effectiveness is speed at or above Mach 3, which is 1 km/s here on Earth (it is still devastating, but somewhat less effective at only Mach 2, about 0.7 km/s). At only Mach 1, there is little such effect, and pretty much none subsonic, which is why with airliner crashes there is always a huge amount of recognizable wreckage on the crash site. The fighter that I spoke of in the earlier post hit near-vertical at about Mach 2.

One kinetic energy weapon that I dealt with, was intended to destroy tanks and bunkers on the battlefield. It was a solid slug of tungsten about 3 inches in diameter pushed by a rocket motor to 5000 feet/sec (near Mach 5). It was to be tube-launched, like a bazooka. The Army tested it against tank armor and concrete bunkers. The prime contractor screwed this up wanting to put beam-rider guidance on it, despite the 1 or 2 second flight time to targets only a mile away. So it wasn't ever fielded.

In 9-inch thick steel tank armor, the entry wound was about 5 inches diameter and the exit would about a foot diameter. The fireball and shock wave and spallation fragments were quite lethal for many yards behind the target sample of armor plate.

For typical bunker construction of reinforced concrete about 5 feet thick, the entrance wound again was about 5 inch diameter, with an exit wound several feet in diameter. Again, the fireball, shock wave, and spallation fragments (a huge quantity) were quite lethal for many dozens of yards behind the target.

The effect is quite real, and quite independent of any chemistry at all.

GW

Last edited by GW Johnson (2023-10-07 08:53:16)

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