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This is a follow up to both SpaceNut (#100) and Calliban ...
Calliban, taking your recommended upper velocity at impact for a Ballistic Cargo Delivery system at 450 m/sec, I came up with a height above Earth adequate to allow for testing the concept here.
The elevation the online calculators came up with is 10,350 meters or (about) 33,500 feet. That elevation is such that I think a balloon would be a better test vehicle than would be an aircraft, unless the US military could be persuaded (somehow) to assist with setting up the experiment. That is remotely possible if there were some reason why the US military would be interested in supporting the research. Admittedly, that seems unlikely.
In any case, I conclude it is feasible to test both your ideas for slowing the cargo pod to 450 m/sec, and for packaging various materials for shipment.
I'd like to remind readers of this topic, that along the line, RobertDyck's call for pulverized regolith for agriculture was pulled into this topic. Certainly a cargo pod traveling at 450 m/sec will have an effect on the regolith it encounters. We can obtain (somewhat) predictive data by running experiments on Earth.
It would be a shame to have to expend sunlight collected laboriously on Mars to pulverize regolith, when the local Package Delivery service can provide powdered regolith as a side benefit of the procedure.
For SpaceNut .... your idea of a crumple zone for the forward section of the cargo pod seems potentially quite useful. There are materials that can be formed under conditions of heat and pressure, and those would be available in the scenario we are discussing here. Diamonds are the first structures that come to (my) mind when thinking about the potential side benefit of this package delivery method, but there very well may be other minerals that could be "manufactured" using this technique.
Edit#1: For those who may prefer non-Metric units ... the proposed package delivery impact velocity would be close to 1,000 mph.
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Calliban:
You asked me a question about entry modeling on Mars with my spreadsheet, in your post 92 above. I ran a little study, but it isn't very possible to put all that data in a simple text post here. I copied images of some of the results into a descriptive word.docx file, and sent it to Tahason43206 to forward to you.
I looked at solid steel spheres entering at 7 km/s, at 2 degrees below horizontal, 30 degrees, and 90 degrees, at several values of ballistic coefficient from very high to very low. My scale height model for density on Mars differs from yours.
I certainly didn't want you think I was ignoring you. It just took a while to do this and collate it into one place.
GW
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For SpaceNut re account ... we have an email from GW Johnson with attachments
For GW Johnson ... thanks for the files ... I'm holding them for Calliban
For Calliban... In honoring our confidentiality agreement with our members, I'd like to ask your permission to forward the files from GW Johnson. I would propose to use the email account you have on file with the forum.
(th)
Recruiting High Value members for NewMars.com/forums, in association with the Mars Society
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I was visiting GW Johnson website earlier in the day and noticed a new write up.
I am wndering if an upper atmospheric Drag chute made of the adapt material with possibly long sky crane cable wrinch and an inflateble ring to force it open, ring guard venting for pressure build up control for slowing down as we would not care if it burns up or is released once peak temperatures have passed.
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For SpaceNut re #104
This topic is generating the kind of creative thinking that is a feature of this forum!
Thanks for the update re GW Johnson's blog!
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Calliban:
You asked me a question about entry modeling on Mars with my spreadsheet, in your post 92 above. I ran a little study, but it isn't very possible to put all that data in a simple text post here. I copied images of some of the results into a descriptive word.docx file, and sent it to Tahason43206 to forward to you.
I looked at solid steel spheres entering at 7 km/s, at 2 degrees below horizontal, 30 degrees, and 90 degrees, at several values of ballistic coefficient from very high to very low. My scale height model for density on Mars differs from yours.
I certainly didn't want you think I was ignoring you. It just took a while to do this and collate it into one place.
GW
Gary, many thanks for looking into this. I look forward to looking at the results.
For SpaceNut re account ... we have an email from GW Johnson with attachments
For GW Johnson ... thanks for the files ... I'm holding them for Calliban
For Calliban... In honoring our confidentiality agreement with our members, I'd like to ask your permission to forward the files from GW Johnson. I would propose to use the email account you have on file with the forum.
(th)
Yes that would work for me. It will be interesting to compare the results.
Last edited by Calliban (2021-02-15 16:59:58)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Time line in the 2020 rover post for its landing may give valuable information
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Doh! I have just had a Homer Simpson moment. I made a serious miscalculation in my spreadsheet. For an oblique entry at 90° to surface at an entry speed of 5.5km/s, the effective plasma temperature ahead of the heat shield exceeds 4,700°C for about 12 seconds. Basically, most of the kinetic energy of the package is dumped into the atmosphere very quickly, which then forms a hot plasma in front of the heat shield.
The radiation temperature at the surface of the heat shield exceeds the sublimation temperature of carbon (3600°C). I have no experience modelling heat transfer at those sorts of temperatures. Some heat will be re-radiated from the surface at its sublimation temperature. Some will be absorbed in the surface as it heats to sublimation. More will be absorbed as the material changes phase from solid to gas and then ionises into plasma. But suffice to say, this is not anywhere near as easy a design problem as I thought. It may in fact be impossible within the rather stringent mass budget that I calculated previously. I will tinker with it some more.
In addition, the atmospheric model that I was using makes the Martian atmosphere unrealistically compact. In reality, the simple scale height models will breaks down in the ionosphere, as tri-atomic CO2 is replaced by a more complex mix of ions. Trying to include those effects into a simple spreadsheet would be complicated and is probably a lost cause. So I will stick with the compact column density based model and accept the fact that it may give pessimistic results.
Last edited by Calliban (2021-02-16 10:09:59)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban and GW Johnson ... at 11:14 local time, I just found your posts and will take care of the transfer shortly, but not immediately.
For Calliban re #108 ... thank you for continuing to analyze the potential of this delivery method.
It should be possible to model the delivery "experience" of the proposed cargo containers on Earth, by dropping them from a balloon (or an aircraft designed to fly that high if one is available and dropping a test object is practical).
This may be a good time to inquire about the practicality of vanes designed to travel with the cargo to release point tucked back behind the cargo pod. At the point of release, they would be allowed to spring out at an angle relative to the central axis of the cargo pod.
These would then act in a manner similar to the cone of a shuttlecock, to provide significant drag while they last.
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Those heating difficulties are one reason shallow-angle trajectories are preferred, even for unmanned vehicles. The peak stagnation heating rates are simply far lower, because you build up the friction slower. This shows up in lower peak deceleration gees as well.
The shape of the entering vehicle also plays a huge role in stagnation heating rates, too. The larger you can make the "nose radius" of the surface facing the wind blast, the lower the heating will be. That also makes the hypersonic drag coefficient larger, which makes ballistic coefficient lower, and in turn lets you come out of the hypersonics at a higher altitude on Mars.
That's why the very bluff heat shield shapes on space capsules like the Mars probe aeroshells, Mercury/Gemini, Apollo, and Dragon work as well as they do. The drag coefficients for shapes like those fall in the 1.4 to 1.7 class. The drag coefficient of a sphere is only about 0.92, according to an old Rand Corp report I found.
I ran a couple of Earth orbit entry studies for a couple of spaceplane concepts a few years back. These were unusual in that they entered dead broadside belly-first, which required folding the wings out of the wind blast in some way. I used the very shallow entry angle afforded by deorbiting with a surface-grazing transfer ellipse. That's about 1.6 degrees below local horizontal at 140 km entry interface from typical low Earth orbit.
By making the belly fairly flat (radius on the order of overall fuselage length), I was able to reduce stagnation heating to the point that re-radiation from a black-surfaced low density ceramic could handle all the peak stagnation heating, without its surface temperatures exceeding the 2350 F solid phase-change point typical of auminosilicates, that causes shrinkage and cracking upon cooldown.
I needed NO carbon-carbon nose-pieces or leading-edge pieces doing it that way! The rest of the vehicle in the wake zone could be left white, or even just bare metal (but not aluminum). Those aft-side surfaces see the same driving temperature as the heat shield, just at an order-of-magnitude-or-more lower heat transfer coefficient. But you only have to survive a few dozen seconds of this. (That's why entry is a fundamentally-transient heat sinking problem, not steady-state at all.)
The low peak deceleration gees also corresponded to low stagnation-point pressure on the heat shield, which the low density ceramic can survive. That is an artifact of the shallow entry angle. At steep entry, the decelerations are far higher, so the pressures are far higher, and would crush the material.
If you know peak gees, then you know the peak deceleration force from the mass of your vehicle. That force divided by the blockage area is the peak average pressure on the heat shield. The stagnation peak pressure would be at least 2, and likely no more than 3, times higher. And that peak is what your heat shield material must be able to tolerate.
GW
Last edited by GW Johnson (2021-02-16 10:40:05)
GW Johnson
McGregor, Texas
"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #110 and Calliban re topic ...
Is this discussion evolving in the direction of a flying saucer?
The images created by your descriptions of the oblate shields reminded me of faked images of flying saucers, and artists renderings of what they might look like.
It this situation, I am imagining the payload package riding in the center of a saucer shape designed to face deceleration flat on at first, and then to gradually bend over to an airfoil shape to achieve control over destination targeting. SpaceNut's "crumple" design might come into play if the impact is designed so the edge of the saucer is first to encounter the regolith.
(th)
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TH:
Well, sort-of.
If you use a traditional large-radius heat shield shape, you may or may not need a backshell around your payload with a tumble-home angle between 15 and 35 degrees. Depends upon whether your payload can tolerate brief exposure to plasma temperatures at low heat transfer coefficients and the low heating rates implied. The tough payloads Calliban is considering probably need no backshell.
Depending upon the locations of center of gravity and center of pressure, you may have something that is naturally stable during the hypersonics. If so, that eliminates the need for any attitude thrusters on the entering package. The heat shield itself is just a slab of some convenient ablative. Such as a simple silica phenolic. You might even get away with a thick piece of wood, if the grain can be oriented right, and you choose something really tough, like Bois d'Arc.
To control speed at impact, I would suggest deploying an inflated ballute. Whatever deploys it can also release the heat shield from the payload. That ballute can be done pretty much like a scaled-up car airbag. Just let it trail behind on a line, and size it large to get a decelerating effect. You come out of hypersonics at around 700 m/s on Mars. You only need to slow to Calliban's 450 m/s before impact.
The size of the entering package will be set by the end-of-hypersonics altitude achievable. Ballistic coefficient and entry angle control that. I suspect no lower than about 15 km deploy altitude, to get some beneficial effect out of your ballute. Maybe 20 km. That will limit your ballistic coefficient to something like 100 kg/sq.m or not much more. Which limits the size of your package, because of the square-cube laws. Ballistic coefficient is proportional to dimension, all else equal.
GW
Last edited by GW Johnson (2021-02-16 11:14:15)
GW Johnson
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"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #112
Thanks for considering the "flying saucer" concept .... I'm not sure how far a design team could go with it, but at least it ** appears ** you have not discounted it completely.
Regarding the ballute .... I can definitely see that option drawing serious attention as the payload mass rises.
The competitive situation (as I see it) is defined by the savings of delivery using Void's idea (with necessary modifications) compared to our friends in the soft-delivery sector, who will be trying to reduce ** their ** costs to stay ahead of ** their ** competition.
It seems to me likely the Ballistic Delivery folks are going to have the delivery of solids of various kinds locked in.
I'm also intrigued by the possibility they may be able to deliver tanks of much needed gases, such as Oxygen and Nitrogen, both of which are in short supply on Mars. The make-your-own gases on Mars crowd are going to be spreading out Louis' solar panels for all they're worth, buffing off dust every morning and collecting output from their extractors as it becomes available.
Meanwhile, the Ballistic Cargo Delivery folks are going to have a field day delivering containers of needed gases to the customers with guaranteed delivery on time and on budget. Those gas containers are going to need SpaceNut's crumple zone buffering, no doubt.
***
I just sent the files to Calliban.
***
(th)
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I'm thinking you need a backshell to prevent compressed gas bottle exposure to entry plasma, even though the exposure is short. Heating raises pressure and weakens the metal, but the real risk is the polymer seals in the tank valve. I also have severe doubts about such a gas bottle surviving a 450 m/s impact intact.
There was a delivery method the Russians used for air-dropped items up to and including army tanks, back in the 1950's and 1960's. These were coming down way too fast on chutes, which is exactly what happens with just about anything and everything on Mars. Up at the shroud line junction, there was a cluster of solid braking rockets, canted to blast around the payload below them. These are what suddenly slowed the payload to an acceptable touchdown speed, firing at the last second. You use an altitude proximity trigger for that.
I'm thinking a cheap one-shot ablative slab of a heat shield, a minimal backshell made of thin aluminum coated with a urethane foam to ablate, an inflatable ballute for deceleration from Mach 3 down to high subsonic, and a cluster of last-second solid braking rockets on the tow line with the ballute. Each of these, loaded, is around a ton or two.
You dump a few pallet-loads of these things out the cargo hatch of whatever takes them to Mars, and let them free-enter the Martian atmosphere while you fly on by, on your interplanetary trajectory. They are a sort of shotgun-pattern of very "dumb" reentry payloads, so you'll need a radio location transmitter on them to find them on the surface. The shotgun pattern may be a couple of hundred km wide on Mars. Do the braking rockets right, and you could land some modestly-fragile stuff.
GW
GW Johnson
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"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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For GW Johnson re #114
for Calliban re topic
For SpaceNut keeping an eye on things ...
The cargo need not be inside a fuselage for the trip to Mars.
The extra contraptions you've indicated are necessary should be able to ride inside their housing in the cargo delivery package until they are needed.
One thing I would look for in development of this delivery method is precision steering to prepared landing sites.
Modern ballistic missiles are able to steer themselves with considerable accuracy. No doubt the exact performance of these systems is classified, but I think it should be possible to develop packages for civilian use that would be accurate to the meter, and thus landing pits can be prepared ahead of time to allow for gradual deceleration instead of an immediate stop.
The pulverized regolith that RobertDyck has indicated would be an asset for agriculture should be a useful byproduct of this delivery method.
Looking beyond the early pioneering, whatever becomes the "FAA" for Mars is going to be intensely interested in ALL incoming traffic, whether planned as soft landings or ballistic as in this topic.
Thanks for thinking about the enhanced deceleration hardware and procedures that may prove necessary for tanks of gas.
While the costs of preparing for survivable landing are going to be greater than for a more robust shipment, the costs should ** still ** be lower than those for any of the soft-landing approaches competitors might offer.
I'd like to see some computer simulations of SpaceNut's crumple zone idea ... it may turn out to be not only workable for the primary purpose, but useful for creating minerals that need high temperature and high pressure to give constituent atoms the neighborly "feelings" that allow them to bond more tightly than is possible under less robust circumstances.
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Many thanks for the feedback GW and the effort you put in. Thanks also TH for forwarding the Word doc.
I have adjusted my model to recalculate scale height across each element, as a function of temperature and gravity at that height. However, it turns out that both density and temperature of the Martian upper atmosphere vary a great deal, making any accurate atmospheric model pointless.
https://agupubs.onlinelibrary.wiley.com … 08JE003086
However, I get an atmospheric density of 2.05E-9 kg/m3 at 135km, which compares to a value of 3E-9 in the table in the word document. So I think overall my model is improved. For the 3mm solid steel ball entering atmospheric deceleration at a velocity 7km/s at 135km (as modelled by Gary), I get a speed of 700m/s at an altitude of 18.54km. Peak temperature is 4851K (4578°C). This appears to be about the same.
To achieve a 450m/s speed at a height of 5km, a payload housed within a 1m diameter spherical heat shield must weigh no more than 31kg, including heat shield. Radiation temperature at dead centre on the heat shield reaches a maximum value of 5959K (5686°C). Radiation heating across the shell reaches a maximum value of 59.75MW and exceeds 10MW for 13.1 seconds.
The problem with these sort of heating rates in normal ceramics is that they lead to huge thermal gradients. This in turn, leads to cracking, which would be aggravated by the heavy deceleration forces on the shield. So ceramic fibre reinforcement would appear prudent. One way of both cooling the heat shield surface and reducing the plasma cloud temperature, would be to bleed steam through small pores in the heat shield at the peak acceleration stages. The OH bonds would start to dissociate at 2000K and dissociation is almost complete at 5000K. A 50% dissociation absorbs about 30MJ/kg of heat, not including the energy needed to boil and raise the gas temperature to dissociation point. So injecting a small mass of water during the most intense heating phases of entry, could reduce ablation substantially.
I am conscious that the point of the sort of ballistic delivery being discussed here is to provide a cheap means of delivering materials and robust components to the Martian surface. To meet this end, it is wise to avoid unnecessary complexity. The entry vehicles need to be self stabilising without active attitude control. To achieve this, most of the mass must be at the front end. This makes the idea of a crumple zone difficult. I like the shuttlecock idea.
More tomorrow.
Last edited by Calliban (2021-02-16 18:10:35)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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post 9, 57 and 67 as well as Robertdyck's 76 cover the air bags, ballutes and more.
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For Calliban re #116
First, thanks for confirming the forward worked....
Second, please note that (should you so choose) you and Dr. Johnson are now able to communicate directly.
I am making the (gamble) guess that the two of you do not need me to serve as a go-between from now on!
I am honored to have been able to play a small role in helping the two of you to collaborate, and hope to be able to serve others in a similar way if there is a need.
Third, thank you for adding the water cooling idea to the discussion! I'm reminded immediately of discussion of fluid cooling (I think it was in connection with Elon Musk/SpaceX thinking about how to deal with aerobraking heating for Starship, especially when returning from Mars).
To find that idea introduced into this topic is most encouraging.
This may be too much to ask, but could this concept stretch far enough to:
1) increase the mass that can be delivered in a shipment and ...
2) reduce the need for extra paraphernalia that GW Johnson has indicated is needed to reach the target velocity of 450 m/sec
I accept that some form of drogue (I like the robust nature of an inflated bag over the risk of incorrectly opening parachutes) will be needed.
Potentially the drogue could be released just before impact of the primary cargo carrier so that the drogue (and it's tether) would arrive later and more gently, due to the lesser mass (a) and (b) the effect of drag on the drogue without the attached payload.
Thus, potentially, the drogue and it's gaseous content could be salvaged, so that once again, the goal of total use of ALL components of the package can be achieved.
Thinking out loud here ... the little radio locator beacon could be part of the drogue, so that it would have an increased chance of survival and therefore increased chance of aiding in timely recovery.
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SpaceNut ... please start thinking about how this forum can begin to attract the attention of business people to fund a series of on-Earth tests of the technology under discussion in this topic.
The 450 m/sec velocity can be achieved by dropping a test article from a balloon, and a number of balloon operators are now in business in the United States and (I am pretty sure) around the world.
The cost of a test of a robust shipping container, including design, manufacture, balloon launch and data collection should be in the low thousands of US dollars. I'd like to see a variety of tests carried out with various deliverables, such as gases (discussed earlier), solid metals (purified for immediate use on Mars), and food stuffs or agricultural materials such as seeds.
Edit#1: A pure Silicon cylinder could be delivered in this manner, thus providing a dramatic running start for a Mars-located semiconductor industry.
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, SpaceNut ... please start thinking about how this forum can begin to attract the attention of business people to fund a series of on-Earth tests of the technology under discussion in this topic.
We are really not inventing anything new here in this topic and the big space companies are already doing these sorts of testing already not just NASA....
R&D is costly and thats why you buy from NASA what you need as a business and steal as many engineers as one can.
There have been many chances to do good for man kind here on earth and the plausible future for mars.
The massive need for power backup is one of those which is needed not just commodity delivery.
The Red Dragon capsule could deliver from sensitive items of probably 4 mT to for the do not care 13 mt as a currently package space x Falcon 9 heavy for under 200 million plus cargo costs per shot.
But if we are doing trade its not going to work....
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For SpaceNut re #119
Your post here has the effect of reducing incentive for members to contribute to development of the topic.
It is not helpful to refer to the achievements of others, when members of the forum are learning or re-discovering new information about how the Universe works.
The big space companies are doing lots of things, and that is (probably) all good. It has nothing to do with development of ideas and knowledge in this forum.
Research and Development takes investment of time and thought, and some energy.
No one buys anything from NASA (to the best of my knowledge). To the best of my knowledge, everything NASA produces is free to the public.
The need for power backup is important, but that belongs in another topic.
This topic is organized for the purpose of developing trade, so if there are any issues that need to be dealt with, they will.
In short, I see this topic as having significant potential to lead to development of actual business activities, in parallel to development of interplanetary transportation in RobertDyck's Large Ship topic.
The people who are going to settle Mars are alive and (most probably) still engaged in education on Earth. A few are graduated and entering careers that will lead to their assuming places of leadership of teams that will, like those formed by Elon Musk and Jeff Bezos, build the systems and procedures that will come into being in the decades ahead.
I am encouraged by the creative thinking (and engineering calculations) of Calliban, combined with the insights provided by GW Johnson.
Now is a good time for us all to think about how we can assist as we may be able.
(th)
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If I understand correctly, and no guarantees there, this thread's fundamental concept was to shoot hard supplies to Mars almost as if from a gun, and let them run smack into Mars totally uncontrolled. The idea was uncontrolled entry, followed by direct high-speed impact with the surface.
Much of what has been recently discussed was ways and means to approach this ideal. The answer is (1) that you will have to control the approach to achieve entry at shallow angles, (2) you will likely need a sacrificial heat shield of some sort, and (3) object size may be limited by the penetration altitude coming out of hypersonics: you have to slow from Mach 3 to Mach 2 or under at impact.
Is that a correct understanding?
I rather doubt that any designs trying to achieve those 3 will save you a lot over delivery by something like a Red Dragon. Instead, it is the vehicle you launch from Earth, and how you agglomerate a cluster of smaller entry objects into a payload that vehicle can carry, where you will achieve your savings, if any.
The downside you fight is the circular error probable of your cluster of entering objects. These things will come down in an ellipse hundreds of km in size, unless you invest heavily in the approach control, and possibly the maneuver-during-entry of the objects. What costs more, those control items, or having to drive thousands of km all over Mars's outback looking for them?
Tough question!
Honestly, 4 ton payloads in a Red Dragon launched by a Falcon-Heavy looked pretty good to me. Especially with an $85-90 M price per launch. That's about $22M/ton delivered to the surface of Mars. That's $22,000/kg = $10,000/pound. That's lots more expensive than going to LEO, but incredibly cheap compared to all other currently-operational ways to put stuff on Mars. And you can send fragile stuff that way, too.
Maybe Starship/Superheavy will be cheaper, maybe not. We'll see, if they get it working reliably. Falcon-Heavy actually is flying. Red Dragon has been cancelled, unfortunately.
I'm not at all sure there is a way to beat that kind of delivery, even if we can let hard payloads crash. You've got roughly a 1 ton limit to your crash vehicle size, if you expect to decelerate to 450 m/s before impact. Higher masses in one object will inevitably require retro-propulsion landings, which is what Red Dragon was all about.
I may be wrong, but I think that is where we are with this notion. A cluster of max-1-ton objects that can enter separately from one another, equipped to decelerate to 400-450-ish m/s before uncontrolled impact. This cluster needs to fit where a Dragon would have fitted, atop a Falcon-Heavy, which means you can send maybe 10 of these 1 ton objects in that cluster to Mars. For about $90M per launch.
That's $9M/ton = $9000/kg = ~$4100/pound, about half of what Red Dragon delivery would have cost. That's assuming the heat shield and ballute are negligible in mass compared to the hard payload itself. You separate the cluster after precision approach, just before entry. That means you need a cluster carrier with precision guidance and some small course-correction dV capability. It gets sacrificed, the same way a Red Dragon would have. (You get to reuse nothing that you don't soft-land.)
I honestly don't see any better way to try to do this. Comments?
GW
Last edited by GW Johnson (2021-02-17 14:10:53)
GW Johnson
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"There is nothing as expensive as a dead crew, especially one dead from a bad management decision"
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I'm not sure what Void originally had in mind, but I cannot see gun launched projectiles being accurate enough to be useful in delivering materials to Mars. And gun launch would be limited to the same launch windows as rocket launch. For most of the time the gun would sit in high Earth orbit, waiting for the planets to line up. It must then fire accurately enough to hit the Martian atmosphere at 400 million km range. I cannot see that working. And the acceleration in a gun barrel, even a kilometre or more in length, would make entry forces appear tame in comparison.
My idea was that we launch a modified Starship upper stage into LEO. The upper stage would be filled with tubes, rather like torpedo tubes, which would contain Mars entry capsules. We refuel the upper stage in LEO, fill the tubes with entry capsules and then send the upper stage on a free return trajectory to Mars. Days or hours before closest approach, we push the capsules out of the tubes using compressed gas, with enough speed to put them on a collision course with Mars. I don't know how precisely we could control the point of impact with the upper atmosphere. Maybe we could string the capsules together using something that would burn away when they hit the atmosphere? The empty upper stage would then flyby Mars without slowing down and would return to Earth on the free return trajectory, where it would be captured into an elliptical orbit via aerobraking. After several passes through the atmosphere, the orbit apogee would reduce to the point where a small additional burn would raise perigee to 400km and the stage will be in LEO once again. The cycle would then repeat. New capsules would be loaded into the tubes and the stage would be refuelled in orbit.
The idea of the ballistic delivery was to provide a cheaper way of delivering hardy components and useful materials to the Martian surface. With the possible exception of the heat shield and the mass of the upper stage, all of the material launched of trans-Mars trajectory is useful payload in one way or another. The projectiles are uncontrolled, relying on a skewed centre of gravity to achieve the correct alignment. There is no envisaged mechanism built into the projectiles aside from a radio location device. They slow to Mach 2 prior to impact by virtue of the aerodynamic drag of the heat shield. On impact, the payload, which is essentially a shell mounted on the heat shield, will pass through the shield into the ground, dissipating any remaining kinetic energy. The heat shield would probably be reduced to scattered fragments.
The validity of the idea rests on the assumption that it would be cheaper to deliver needed materials and parts this way than it would by controlled landing. But we are indeed assuming that it will be relatively cheap to have an EVA team that scout a large area of Martian surface picking these things up. EVA time is known to be expensive. If the capsules are distributed over an ellipse 1000 miles in length, then I doubt it will be cheap scouting half a million square miles for errant capsules. A trade study would need to be done to consider relative costs.
Last edited by Calliban (2021-02-17 17:15:25)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban and GW Johnson ...
Thanks to both of you for your continued development of this topic!
It seems to me a well designed ballistic delivery system will ALWAYS be cost competitive with the soft landing folks.
The high precision landing electronics can be and surely will be manufactured in billions of units for pennies. Simple vanes can steer the projectile, just as the Falcon Nine first stages are demonstrating. Calliban's ballute is an interesting addition to the flight package, to increase the size of the package mass.
The idea of shipping tubes of delivery packages to Mars on a free return trajectory seems very attractive.
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For Calliban ... there will ALWAYS be competition for space on soft-landing vehicles. That competition will raise the price for those services.
The Ballistic Delivery folks can set their prices just below whatever the soft-landing folks are charging, and rake off excess profits.
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Calliban ... I see no need for scattered delivery as your description suggests .... Furthermore, whatever is the Mars equivalent of the FAA is going to require and expect precision delivery.
Edit#1 for Calliban:
For Calliban re navigation electronics ...
https://www.wired.com/story/researchers … ket-newtab
Their simulations estimated that a 6-centimeter plate could carry 10 milligrams of cargo in the mesosphere under natural sunlight. Ten milligrams may not sound like much; a drop of water weighs five times as much. But engineering advances have shrunk silicon chips into dust-sized sensors far smaller than that. These “smart dust” systems can fit a power source, radio communication, and a data-collecting sensor in cubes only a millimeter across. “Researchers can do a lot when you give them a cubic millimeter of silicon,” says Bargatin. “And a cubic millimeter of silicon weighs a couple of milligrams.”
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For Calliban re topic ....
In thinking about logical development of this topic overnight, I came up with this ...
Most materials for a landing pad for Mr. Musk and his Starships could be delivered by ballistic means.
I'm thinking of concrete, steel rebar and forming elements. The pulverized regolith should be (your judgement here) useful for fill?
Work could be done by teleoperations with personnel cited at Phobos, or in one of RobertDyck's Large Ships if he can get one build and flying in time.
Some components of a nuclear reactor would need to be soft landed, but I'm guessing that passive materials could be delivered by ballistic methods.
If we (humans) allow ourselves to think about the Mars effort as a Normandy Invasion, it would help to focus thought on parallel efforts.
A robust nuclear reactor would help greatly to expedite construction of such elements as a landing pad, and preparation of fuel for return to orbit.
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For Calliban after Perseverance landing ...
https://telegraf.id/nasa-perseverance-r … g-on-mars/
Parachute deployment
Once the spacecraft has slowed down to less than 1,000 miles (1,600 kilometers) an hour, it’s time to deploy the 70.5 feet (21.5 meters) wide supersonic parachute at an altitude of seven miles (11 kilometers).
Perseverance is deploying a new technology called Range Trigger that decides the precise moment to deploy, based on the craft’s position relative to the landing site.
Asked to name the single most critical event, NASA’s EDL lead Allen Chen said: “Obviously there’s a lot of concentrated risk in supersonic parachute opening.”
Per Google:
Convert 1,600 Kilometers per Hour to Meters per Second
https://www.calculateme.com/speed/kilometers-per...
26 rows · A kilometer per hour is a unit of speed. Something traveling at one kilometer per hour is traveling about 0.278 meters per second, or about 0.621 miles per hour.KM/H M/S
1,600 444.44
For Calliban ... the velocity you found for a ballistic delivery was 450 m/sec, if I recall correctly.
I was paying close attention during the landing today, and I ** think ** I heard the play-by-play announcer report the velocity at the moment of chute deployment as 530 m/sec, which would have been a bit more than predicted.
Apparently there will be a lot of video about the landing to be published after it is retrieved from Maven, which recorded transmissions during the landing sequence.
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