Ballistic Delivery of Supplies to Mars: Lithobraking

GW Johnson · 2021-03-14 14:55:32

Dynamic pressure q = 0.5 rho V^2 = 0.5 P gamma M^2. If you know velocity and density, that form is more convenient. If you know pressure and Mach number, that form is more convenient. They get the same answer. "Gamma" is the specific heat ratio for the atmospheric gas, which is about 1.4 for Earthly air at ordinary conditions, and about 1.33 for the triatomic carbon dioxide on Mars at conditions there.

Drag force F = q CD A, where the CD has to go with the A that you use, as the basis of the CD data. Most aero decelerators have blockage area Ao CD's of 1 to about 1.5. That would be true at supersonic speeds. About the only supersonic-capable chute designs that I know of are the ribbon chute (max Mach 2) and the ringsail that JPL has been using on its Mars landers (max Mach 2.5). Survival of opening shock is really "iffy" at max Mach, by the way. Survival is a lot better if you slow down about half a Mach from max. If you have the time available before impact.

The video image in post 149 above is a ringsail chute. I'd hazard the guess that it is from a Mars lander chute test conducted at about 105,000 feet above the surface of the Earth. JPL has used the ringsail successfully on all its probes since 1976's Viking landers. It is the gap between the ring and the center canopy that keeps the ringsail from exploding when opening at supersonic speeds.

That is why they are made of kevlar: to survive that supersonic extreme force. But kevlar's lower elongation to failure puts limits on how fast the airstream can be moving. Doesn't work at Mach 3. Barely works at Mach 2.5. Works really great at Mach 2 and slower. But only in air that thin!

I have used nylon ribbon chutes successfully as Mach 1.1 drogues, at sea level pressures. But no faster. Faster requires thinner air. The spaces between the ribbons provide the venting, similar to the gap in the ringsail. Terminal velocities at the same diameter are higher with ribbon chutes, because they have more venting area. Drogue only, not for use as a main chute.

I have also used grocery store grape bag mesh as a supersonic sea level drogue at similar speeds, even a bit higher (Mach 1.3 in Boeing's wind tunnel). But it has inherently less drag, and thus far higher terminal velocities down in the dense air. Useful as a drogue only, not a main chute. Fly much faster, and it is at risk of melting from air friction heating.

You do NOT have time to fuss with drogues on Mars, even at 10+ km altitudes. You have to open a main chute immediately, for it to have time to do you any good. That is why JPL uses the ringsail.

GW

Last edited by GW Johnson (2021-03-14 15:04:26)

SpaceNut · 2021-03-14 18:32:14

This parachute fails as mass is increased that it's trying to not only slow but give buoyancy or lift to. The chute needs to grow in size as the mass is slowed not to mention must grow is size as mass is increased.

tahanson43206 · 2021-03-14 20:52:57

It is time to remind everyone that there are other topics to talk about parachutes.

** This ** topic is NOT about parachutes!

No parachutes are allowed in this topic!

Der Parachuten Verboten!

(That's in honor of our new member, Noah, who is from Germany)

Edit#1: Noah provided **real** German for this request:

Here is Noah's recommendation for my parachute admonition in the Ballistic Delivery topic:
Diskussionen über Fallschirme sind verboten!

Somehow an enthusiastic parachutist dropped off a post in this topic, and it took off for a vigorous run!

This topic is intended to provide a gathering place for those who will be building successful business ventures delivering non-perishable supplies to Mars using Ballistic Delivery techniques, as carefully worked out by Calliban and GW Johnson, and as supported by NASA's delivery of Perseverance components to the magic velocity of 500 miles per hour after the deceleration run through the atmosphere.

Edit#2: As SpaceNut pointed out in posts after this one, the actual velocity of the Perseverance package was greater than 500 mph. In fact (if memory serves) the actual velocity was 940 mph. In light of Calliban's recommendation to drop the velocity to 500 mph for successful impact of sturdy payloads in a properly prepared landing patch on Mars, I am hoping that further refinement of the design demonstrated by NASA will permit operation of a landing package at velocity at or below 500 mph at impact.

(th)

SpaceNut · 2021-03-15 17:31:30

That means no heat shield as all which is an upside down attacked parachute as what it does is create lift and drag just the same as the fabric kind. The difference is one is all the time open for use due to air friction while the other is large and does not see air friction when used.

Ballistic entry to impact does not slow down beyond basic shape and abrasive material that is lost due to heat. To survive any of this without any efforts means a field debris the size of a creator and molten slag. Just like a meteorite.

Value is higher in mach numbers of 3.5 sound with heat shield not 500mph. That happens after parachute use. So if you want all of those terms removed to a new topic we will call it parachute dynamics and heat shield.

As a bunker buster lands at the surface at less than 100 mph from altitude not 7500 mph or higher depending on shape plus entry speed which is not going to survive.

tahanson43206 · 2021-03-15 18:05:31

For SpaceNut re #154

The package seems to have settled down into the form of a saucer shaped heat shield payload enclosure.

The example of the Perseverance lander package is compelling ... the heat shield saucer package took the system down to the "magic" velocity of 500+ miles per hour, without the parachute (as I understand it).

I'm certainly open to correction on that point, but if that summary of what was achieved is correct, then the Ballistic Delivery system does not need a parachute. In Calliban's analysis of the system (as I remember it (again subject to correction)) the payload can be expected to survive impact and be available for immediate retrieval from the impact site, which will itself be well known due to real time radio transmissions from the package during descent.

I'm picking up on your text about where specific velocities are achieved, and will plan to go back and reread the topic.

(th)

SpaceNut · 2021-03-15 18:22:36

Found orbital entry is 12,000 mph when the Perseverance deploys its 70.5-foot-wide (21.5-meter) supersonic parachute at an altitude of about 7 miles (11 kilometers) and a speed of about 940 mph (1,512 kilometers per hour). The back shell and heat shield are gone at that point. Of course these numbers change with increasing mass upward for the same diameter she'll and shield for speed.

Mars mach numbers
https://www.grc.nasa.gov/www/k-12/BGP/mach.html

tahanson43206 · 2021-03-15 18:42:23

For SpaceNut ... thank you for your follow up!

Here is what I found ...

https://www.cbsnews.com/news/nasa-mars- … 021-02-18/

Hitting the thin, mostly carbon dioxide "air" at a blistering 12,000 mph, the spacecraft will rapidly decelerate, enduring heat shield temperatures as high as 2,370 degrees as it slows to just under 1,000 mph within about four minutes.
At that point, at an altitude of about seven miles and a velocity of around 940 mph, a 70.5-foot-wide parachute will unfurl in the supersonic slipstream, slowing the spacecraft to just 200 mph by the time it reaches an altitude of 1.3 miles.

The citation I found was from ** before ** the landing. However, I note that the figures match between what you found and my citation.

What this seems to be saying is that we are in agreement that the velocity had fallen to 940 mph (1,512 km/h) before the parachutes were deployed.

For the purposes of this topic, we can (hopefully) assume that 940 mph (1,512 km/h) is the upper bound of what is possible.

The Ballistic Delivery topic would ** not ** deploy a parachute, but would instead keep steering itself as a flying machine (shaped like a saucer) so that it reaches the intended delivery point.

In order for this topic to become a business, it needs to prove the proposition with which it started as a Vision of Void.

Along the way the topic has taken a beating, as forum members have whacked it with war clubs, the way American Indians used to "entertain" their captives, by making them run the gauntlet.

At this point, I ** think ** the topic is ready for field testing.

The potential for savings in material delivery costs and timing are significant, if the potential of the topic can be realized.

I am open to suggestions on how to proceed from here.

(th)

SpaceNut · 2021-03-15 19:00:52

The mass of the rover, plus crane, retro engine, plus fuel are when totalled for an impactor landing as it staying in there shell will not slow it down any further and if we want heavier payloads delivered we need larger shells to keep the same profile.

I did research for the meteor impacts and its on the 200 total a year. I have a batch of links on paper to add in at so point for a topic.

I think this is the formula for the speed for shell size paper
https://ssdl.gatech.edu/sites/default/f … 0-1210.pdf

tahanson43206 · 2021-03-15 19:35:25

For SpaceNut re #158

Thanks for the link to the George Tech paper from 2010!

SearchTerm:GeorgiaTech paper on Mars Entry, Descent and Landing

Mars Entry, Descent, and Landing Trajectory and
Atmosphere Reconstruction
Soumyo Dutta*
and Robert D. Braun.†
Georgia Institute of Technology, Atlanta, GA 30332-0150

Edit#1 ... I read a little further and came to the (to me astonishing) fact that the work done at Georgia Tech featured ballistic methods to accelerate the test article!

Results from a sample case are presented in this section to test the methodology. As MSL will not provide a data
set until 2012, measurements from a ballistic range test of a Crew Exploration Vehicle (CEV) model is used to apply
the trajectory and atmospheric reconstruction procedures.16 The ballistic range test was conducted on July 15, 2008 at
the Aberdeen Army Proving Ground (APG) in Aberdeen, MD. As shown in Figure 3, the test utilized two titanium
models of the CEV. The models were referred to as the pressure-telemetry modules (PTM). The PTMs were launched
from a ballistics range gun and data was collected for approximately 20 seconds after they exited the muzzle.
Although data sets for both models were available, only the results for the second model (labeled PTM2) are analyzed
below. Some key parameters for PTM2 are summarized in
Table 1. The center of gravity (CG) locations are with respect to U.S. Army Research Laboratory coordinate
system convention.

(th)

tahanson43206 · 2021-03-15 19:45:11

For SpaceNut ... here is a follow up on the paper you found ...

Experience
NASA Langley Research Center Graphic
Aerospace Engineer in Atmospheric Flight and Entry Systems Branch
NASA Langley Research Center
Aug 2013 - Present 7 years 8 months
Hampton, VA
Georgia Institute of Technology Graphic
Graduate Research Assistant
Georgia Institute of Technology
May 2008 - Aug 2013 5 years 4 months
Atlanta, GA
• Research focus on statistical parametric estimation of the performance of planetary entry, landing, and descent systems
• Developed techniques for optimization of flush atmospheric data systems/FADS for entry applications
• Initial development of rapid techniques to generate aerodynamic coefficient for general shapes in rarefied flow
• Advised by Dr. Robert D. Braun
NASA Ames Research Center Graphic
Summer Intern - Graduate Student
NASA Ames Research Center
Jun 2011 - Aug 2011 3 months
Mountain View, CA
Conducted mission sizing and trade studies for a low ballistic coefficient entry system for Venus. Specially did systems engineering work for the Adaptable Deployable Entry Project (ADEPT) mission concept. Problems considered included:
o Evaluation of special considerations needed for shallow entry trajectories and low ballistic coefficient
o Mass sizing of structure needed for a mechanically-deployable entry vehicle at peak dynamic pressure and g-loading
o Payload mass fraction…
Show more
Draper Laboratory Graphic
Summer Intern - Graduate Student
Draper Laboratory
Jun 2010 - Aug 2010 3 months
Cambridge, MA
• Developed tools to conduct Linear Covariance analysis of dynamical systems in lieu of Monte Carlo analysis
• Applied Linear Covariance tool to missile interceptor design especially for boost-phase and post-boost-phase interception
• Conducted parametric analysis of the interceptor design phase, including the effect of initial condition, knowledge and sensor error on mission feasibility
NASA Langley Research Center Graphic
Entry, Descent, and Landing Analyst
NASA Langley Research Center
May 2009 - Aug 2009 4 months
Hampton, VA
• Developed stochastic trajectory and atmospheric reconstruction tools for planetary entries
• Created extended Kalman filtering tool to utilize surface pressure measurements from aeroshell for freestream parameter estimation
• Tested reconstruction tool with data sets from ballistic range data
• Refined methodology to utilize in the analysis of the Mars Science Laboratory dataset
Jet Propulsion Laboratory Graphic
Entry, Descent, and Landing Analyst
Jet Propulsion Laboratory
May 2008 - Aug 2008 4 months
Pasadena, CA
- Developed statistical filtering tools for EDL performance reconstruction. Primarily focused on using extended Kalman filters with inertial measurements and radar altimeter data
- Collaborated on the 2008 Phoenix Lander reconstruction effort
Shaw Industries Graphic
Mechanical Engineering Intern
Shaw Industries
Jun 2007 - Aug 20073 months
Jet Propulsion Laboratory Graphic
Summer Undergraduate Researcher
Jet Propulsion Laboratory
Jun 2006 - Aug 2006 3 months
Pasadena, CA
Michelin Graphic
Mechanical Engineering Intern
Michelin
May 2005 - Aug 20054 months
Education
Georgia Institute of TechnologyGeorgia Institute of Technology Graphic
Georgia Institute of Technology
Doctor of ScienceAerospace Engineering
2010 - 2013
Activities and Societies: Space Systems Design Laboratory, Planetary Society at Georgia Tech
Georgia Institute of TechnologyGeorgia Institute of Technology Graphic
Georgia Institute of Technology
Master of ScienceAerospace Engineering
2008 - 2010
Activities and Societies: Space Systems Design Laboratory

(th)

tahanson43206 · 2021-03-16 07:28:17

Quoting from an edit to Post #153...

This topic is intended to provide a gathering place for those who will be building successful business ventures delivering non-perishable supplies to Mars using Ballistic Delivery techniques, as carefully worked out by Calliban and GW Johnson, and as supported by NASA's delivery of Perseverance components to the magic velocity of 500 miles per hour after the deceleration run through the atmosphere.
Edit#2: As SpaceNut pointed out in posts after this one, the actual velocity of the Perseverance package was greater than 500 mph. In fact (if memory serves) the actual velocity was 940 mph. In light of Calliban's recommendation to drop the velocity to 500 mph for successful impact of sturdy payloads in a properly prepared landing patch on Mars, I am hoping that further refinement of the design demonstrated by NASA will permit operation of a landing package at velocity at or below 500 mph at impact.

Does anyone in the forum (who is currently registered and able to post) happen to know Dr. Soumyo Dutta?

His research on spacecraft design for travel through atmosphere would seem to be a good fit for the Ballistic Delivery project.

In particular, as I understand the paper found by SpaceNut, the research team asked for and received support from the US Army, to test designs for spacecraft heat shields using high powered cannon/howitzer equipment.

The test articles were subjected to (if memory serves) 7000 g's at the point of launch, and they contained electronics for data collection.

This topic includes questions by forum members regarding the capability of an impactor to survive the kinds of g loads that can be expected when decelerating from (about) 500 mph to zero with respect to the Martian regolith.

It would appear that the research reported in the paper found by SpaceNut can provide some reassurance on this and related points.

(th)

SpaceNut · 2021-03-24 20:01:03

The higher the payload mass on orbit the more difficult it is to get something useful from it.
Found a chart for what be the small to asteroid size.
https://www.nextbigfuture.com/2013/11/a … chart.html

The delivery from launch to Mars does not change as it requires all of the stuff a normal ending requires to enter Mars atmosphere.

Size diameter of the controlled she'll can only bring us so far to landing greater mass to the surface of Mars.

http://www.marspapers.org/paper/Christov_2008.pdf

https://space.nss.org/wp-content/upload … o-Mars.pdf

https://sites.nationalacademies.org/cs/ … 083264.pdf

http://robotics.estec.esa.int/ASTRA/Ast … aziano.pdf

tahanson43206 · 2021-03-24 21:21:15

For SpaceNut re #162 ... thanks for helping the topic along!

As a reminder, work earlier in this topic showed the upper bound for a Ballistic Delivery, worked out by Calliban. The upper limit is set by the limitations of the atmosphere, which needs to be depended upon to slow the vehicle to (about) 500 mph for a successful impact landing.

I'd have to go back to look, but my recollection is the payload for a ballistic delivery is still significant. If you (as a Mars customer) order several tons of some commodity (such as metal, Portland cement for concrete, machined parts packed in cushion material, etc), you'll expect to have the shipment delivered in multiple packages.

(th)

SpaceNut · 2021-03-25 17:43:47

That speed was for the entry velocity, that size shell plus shape and for that mass only.

While powdered concrete and water fits the rebar would be limited to the round shape and still needs welding to be performed on site.

The we still need to land a bulldozer, a vehicle to haul ground up regolith plus the means to grind it up, a backhoe or bucket to lift it into the truck and to move it to a cement mixer. This list is greater than the shell dimensions and mass capability.

tahanson43206 · 2021-03-25 17:53:08

For SpaceNut re #164

Thank you for continuing to think about the opportunity and challenges of Ballistic Delivery.

Your comments about machinery reminded me of an option we've not considered (at least that I'm aware of) ...

A well designed Ballistic Delivery might yield a hot bubbly mass of material that could be flattened (by a suitable piece of equipment) as it cools.

I'm thinking of the equivalent of magma that is visible in multiple locations around the Earth where volcano activity produces magma without explosion.

Magma appears to be quite strong. I read somewhere about entrepreneurs sawing magma into blocks/bricks for construction projects.

(th)

SpaceNut · 2021-03-25 18:39:49

Hidden in the zubrin message

The currently operational SpaceX Falcon Heavy could throw a 10-ton class lander to Mars. The soon to be operational NASA SLS and SpaceX Starship booster will be able to send a 20-ton lander.
To get started with human exploration, we need a 10-ton class lander.
There are a number of ways to create such a system. For example, we could use aeroshells, parachutes and landing jets, or perhaps a miniature version of Starship.
I won’t go into the details. But the bottom line is if we can land one ton on Mars, we can land 10. It requires no scientific breakthroughs, just engineering.

That 10 tons setting on the surface not just payload after expending all means to soft land.

tahanson43206 · 2021-03-26 05:49:40

For SpaceNut re #166

Thanks for finding that important section of the Zubrin statement!

The take-away is that ** all ** that landed mass need not include a single kilogram of mass that can be landed cheaply using Ballistic Delivery.

** All ** that landed mass can be (and surely will be) needed for human missions requiring delicate components and critical non-durable supplies.

(th)

SpaceNut · 2021-03-26 18:56:00

https://www.jpl.nasa.gov/images/close-u … an-surface

https://www.google.com/amp/s/www.techno … hield/amp/

https://www.lockheedmartin.com/en-us/ca … space.html

https://en.m.wikipedia.org/wiki/Heat_Shield_Rock

https://en.m.wikipedia.org/wiki/Mars_atmospheric_entry

https://www.google.com/search?q=heat+sh … p6h3C490QM

Edit looking for details of backshell mass and volume.

https://www.nasa.gov/centers/ames/resea … hield.html

Peak shielding heat
https://spaceflight101.com/msl/msl-aero … at-shield/

tahanson43206 · 2021-03-27 05:41:24

For SpaceNut re #168

Thanks for finding all those links to study!

I wish there were someone inspired to pursue this business opportunity!

It would be rewarding to see Void's original inspiration become a ** real ** economic activity!

The situation appears to be that the only place this idea exists on Earth in 2021 is here in this (relatively small) forum.

The idea of settling Mars at all isn't taken seriously by more than a very small number of people on Earth, and the Ballistic Delivery concept is (probably) considered too far out for most of that small number.

I looked at the dark impact point of the heat shield and saw a treasure trove of valuable supplies in the center of the light absorbing material.

I expect the real significance of Ballistic Delivery will show up when an entrepreneur runs circles around the competition by solving the various technical problems to achieve reliability, volume delivery, and lower cost.

Edit#1: https://www.technologyreview.com/2019/0 … at-shield/

Thanks for that 2019 article on the history of heat shield development at MIT and NASA over several decades, and for the detailed explanation of development of the shield that successfully protected Curiosity (and later Perseverance). The details about the blunt shape pushing the shockwave out in front to absorb most of the heat generated by the advance of the vehicle was particularly well written (from my perspective). I note that computer models of turbulence were important factors in the design process, helping to explain why early designs were failing.

In trying to think ahead to successful development of Ballistic Delivery, the value of the heat shield material that impacts the ground ahead of the payload is worth considering. Most of the material left after doing duty will be concentrated Carbon (char) which should be valuable in itself.

I ** think ** it was Calliban who's been describing solid fuel pellets in another topic recently. The residue accumulated on heat shields will be present in the landing location, and it might well be economically justifiable to retrieve it.

(th)

SpaceNut · 2021-04-02 16:43:25

I think they used the wrong term void

Void wrote:

While for a time the "Bread and Butter" of this will be in LEO, if it works at all, at some point it should be possible to move large structures like this from the Earth/Moon subsystem to other locations, such as Mars/Phobos/Diemos.
Ballistic Capture might work for that.
https://www.scientificamerican.com/arti … e%20planet.
Quote:
A New Way to Reach Mars Safely, Anytime and on the Cheap
Ballistic capture, a low-energy method that has coasted spacecraft into lunar orbit, could help humanity visit the Red Planet much more often
The above must be distinguished from topics where we have hard landings of materials onto the surface of an object such as Mars.
Typically it is treated here like a deformed child that is not accepted. Well that does not hurt me. So what. Anyway I mention it again. This method may not require a heat shield to enter Martian orbit. However it does need a subsequent push of some kind to stay in orbit, eventually. Missions of this kind can be launched much more often, and it blends well with space propulsion methods such as ion rockets.
The flight time is longer, so that if you involve humans you must consider what the effects of more potential radiation exposure and more microgravity time may imply. So, if you do have synthetic gravity and radiation protection that is good enough, then you might not mind.
For material goods, though I think it may have value.
It might fit in with electric propulsion methods, and also solar wind propulsion, and perhaps photon propulsion methods.
Done.

Going to pause now.

SpaceNut · 2021-04-02 16:45:10

For the moon it would be gravity capture

GW Johnson wrote:

The description of ballistic capture as I read it, lacks any mention of how you achieve more-or-less Mars orbital velocity about the sun. Most transfer trajectories have velocities or velocity components about the sun that are slower than Mars orbital velocity about the sun, by around 5.5 to 7.5 km/s relative to Mars. Mars escape velocity is 5 km/s. Mars low orbit velocity is 3.5 km/s.
I have real heartburn over the description that Hohmann transfer is higher energy. It is minimum possible total delta-vee to get there from here. Flying faster than Hohmann requires a bigger departure delta-vee. There is the delta-vee to speed up near Mars orbital velocity when you get there, in order not to crash (or enter directly) but to enter orbit. Mars is literally running over you from behind when you get there, almost no matter what trajectory you fly to get there.
The descriptions on the Sci Am site just do not address those physics. Hence my heartburn. There are no orbits about the sun that take you from Earth to Mars, and yet arrive at Mars, moving about the sun at about the same speed as Mars.
GW

SpaceNut · 2021-04-02 16:46:28

GW Johnson wrote:

Void:
I'm not unhappy, I was just rather skeptical of what I was reading in the link you provided.
There are no coasting orbits that I can imagine that would have a velocity at Mars's distance that was (1) comparable to Mars orbital velocity, and (2) be anywhere near parallel to Mars's orbital path, while still passing anywhere near the Earth.
That being said, I thought about it for a while, and realized there is a powered spiral-out path that might work, if the spacecraft were under very low thrust continuously. The only suitable propulsion that we understand would be electric propulsion, meaning ion thrusters. I don't honestly know if solar sailing has the thrust to do it, but it might. I just don't know.
One might do a minimal escape from Earth, turn on the ion thrusters, and slowly spiral out toward the orbit of Mars. You want to limit the the (extremely-slow) acceleration, so that your spiral never departs very far from local circular. That way you are moving pretty much at Mars's speed , and still nearly parallel to Mars's path, when you get there. At least I think it works that way.
That kind of limited-acceleration spiral would be a rather long trip, far longer than Hohmann transfer, for sure. But it is not coasting, it is powered, just not very much.
Most of the ion-powered spiral proposals I had previously seen accelerated to midpoint, then decelerated the rest of the way, to enable a spiral-in type of capture. Even those take longer than Hohmann to get there. If you let your arrival speed get too high, you are moving way above Mars escape when you pass by Mars, and there can be no capture without a large rocket burn. Your velocity will also be significantly non-parallel to Mars's orbital velocity. The usual proposals do the accelerate-decelerate thing in order to cut travel time.
For all I know, maybe even the usual ion-thrusted accelerate-decelerate spiral would work for ballistic capture. The spiral should have a velocity at Mars distance close enough to Mars orbit velocity, so as to be within Mars escape relative to Mars (otherwise there could be no spiral-in). I suppose if you did it "just right", the ballistic capture into orbit could substitute for the spiral-in maneuver.
This ballistic capture thing is definitely a different notion. I just don't know that much about low-thrust spiralling trajectories to say. The link to the Sci Am thing didn't specify a thrusted spiral trajectory, which is what threw me off. I am familiar with ordinary coasting orbits, and there are none that can match the descriptions in the Sci Am ballistic capture thing.
So, I guess the bottom line is this: might work for ion propulsion, maybe solar sailing. Won't work for ordinary rockets that spend most of their time coasting.
GW

SpaceNut · 2021-04-02 16:48:03

Will need to read tomorrow on a computer and not a cellphone

kbd512 wrote:

Here's a paper on the topic of the ballistic capture technique referenced in the Scientific American article for anyone who is interested:
Earth-Mars Transfers with Ballistic Capture by Edward Belbruno and Francesco Tapputo

tahanson43206 wrote:

For kbd512 re #8
Thanks for the link to the paper by Belbruno and Tapputo ... It seems to have been published after 2010, based upon a scan of the references:
https://arxiv.org/pdf/1410.8856.pdf

[2] M.J. Chung, S.J. Hatch, J.A. Kangas, S.M. Long, R.B. Roncoli, and T.H.
Sweetser. Trans-Lunar Cruise Trajectory Design of GRAIL (Gravity Recovery and Interior Laboratory) Mission. In Paper AIAA 2010-8384, AIAA
Guidance, Navigation, and Control Conference, Toronto, Ontario, Canada,
2-5 August, 2010, 2010.
Earth–Mars Transfers with Ballistic Capture
Edward Belbruno1 Francesco Topputo2
1 Princeton University, Princeton, New Jersey 08544, USA
2 Politecnico di Milano, Milan 20156, Italy
Abstract
We construct a new type of transfer from the Earth to Mars, which ends
in ballistic capture. This results in a substantial savings in capture ∆v
from that of a classical Hohmann transfer under certain conditions. This
is accomplished by first becoming captured at Mars, very distant from
the planet, and then from there, following a ballistic capture transfer
to a desired altitude within a ballistic capture set. This is achieved by
manipulating the stable sets, or sets of initial conditions whose orbits
satisfy a simple definition of stability. This transfer type may be of interest
for Mars missions because of lower capture ∆v, moderate flight time, and
flexibility of launch period from the Earth.
(th)

GW Johnson · 2021-04-03 08:55:25

I looked at the paper in Kbd512's link. I can tell they are looking at some sort of 3+ body computer solutions, but I don't understand the full transfer trajectory, because they didn't depict it, only the weird spiralling arrival. I did not understand the words, because it was written in advanced orbital mechanics jargon, not plain English. The jargon terms were mostly undefined. This kind of orbital mechanics is way beyond what I understand how-to-do.

About all I could tell is that there is some small burn requirement they denoted as "vc", to get onto that weird sport-of spiralling capture, into that far elliptic orbit they said was stable. You still have to get from that far elliptic orbit down to something useful, and that will require more burns. Implied is a requirement for very sophisticated guidance and control, plus good attitude control for pointing those burns.

I'm going to hazard the educated guess that the bulk of the delta-vee savings gets eaten up getting from that far elliptic orbit to something more useful. Which makes this choice more of a "wash" than the advertising says. More useful: such as low orbit, or direct landing. Hohmann transfer puts you directly into low orbit, or directly onto the surface. So do the faster elliptic trajectories with shorter flight times (you get what you pay for).

Whatever this technique really is, it is definitely not for just shooting dumb payloads straight to Mars as a launch-and-forget item. That was the original concept of this thread, if I understand correctly. And I believe we established that even with simple Hohmann transfer, there is a precision guidance and maneuver requirement, so that a survivable direct entry window could be hit.

So, there likely is no such thing as a "launch-and-forget" way to successfully shoot dumb payloads to Mars. If you try that, most will miss the planet and be lost in space. Most of the remainder will enter pretty much straight on (at a very steep entry angle in the 70-90 degree below horizontal range), and be destroyed by impact before significant aerobraking can even occur.

Entering nearly vertically, you only have a bit over 100 km in which to slow down. It takes thousands of km of path length to slow down in the thin air (whether there, or here). THAT is why you CANNOT come in steep at interplanetary, or even just orbital, speeds.

GW

Last edited by GW Johnson (2021-04-03 09:05:26)

SpaceNut · 2021-04-03 09:28:05

The sum of it seems to be based on geometry of arcs for the path from one starting point to the next relative to the sun as the alignment point.

From the mars calendar topic of which location and speed of travel can be had for mars.

its not a circular orbit around the center point being the sun so computing location is about timing of movement and recalculation as we progress towards mars from earth being that we want to get ahead of mars orbit for gravity capture at near mars velocities so as to avoid the large fuel burn to slow down from a Hohmann transfer.

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#151 2021-03-14 14:55:32

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#152 2021-03-14 18:32:14

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#153 2021-03-14 20:52:57

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#154 2021-03-15 17:31:30

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#155 2021-03-15 18:05:31

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#156 2021-03-15 18:22:36

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#157 2021-03-15 18:42:23

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#158 2021-03-15 19:00:52

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#159 2021-03-15 19:35:25

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#160 2021-03-15 19:45:11

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#161 2021-03-16 07:28:17

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#162 2021-03-24 20:01:03

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#163 2021-03-24 21:21:15

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#164 2021-03-25 17:43:47

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#165 2021-03-25 17:53:08

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#166 2021-03-25 18:39:49

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#167 2021-03-26 05:49:40

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#168 2021-03-26 18:56:00

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#169 2021-03-27 05:41:24

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#170 2021-04-02 16:43:25

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#171 2021-04-02 16:45:10

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#172 2021-04-02 16:46:28

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#173 2021-04-02 16:48:03

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#174 2021-04-03 08:55:25

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

#175 2021-04-03 09:28:05

Re: Ballistic Delivery of Supplies to Mars: Lithobraking

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