New Mars Forums

Official discussion forum of The Mars Society and MarsNews.com

You are not logged in.

Announcement

Announcement: As a reader of NewMars forum, we have opportunities for you to assist with technical discussions in several initiatives underway. NewMars needs volunteers with appropriate education, skills, talent, motivation and generosity of spirit as a highly valued member. Write to newmarsmember * gmail.com to tell us about your ability's to help contribute to NewMars and become a registered member.

#176 2021-04-03 09:49:18

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For GW Johnson .... thank you for noting the purpose of this topic.

Because of the Flow-Under-the-Bridge nature of this forum, is is constantly necessary to refresh the purpose, and also to refresh the achievements of the topic, which include:

1) Identification of a velocity at which arriving packages can be expected to survive impact (courtesy of Calliban)
2) Identification of trajectory which, in combination with suitable packaging (heat shield, et al) will deliver velocity of (1)
3) Other factors I have forgotten, but which are safely stored in the forum archive

I am persuaded that a viable business opportunity exists for an individual who can build an organization, or for an existing organization, wishing to compete in this space.

We have had some wild excursions from the stated purpose of this topic along the way, and no doubt those excursions will continue into the future.

I would very much like to see someone take on this business opportunity and begin the process of setting up shop in time for major activity in settlement of Mars.

(th)

Offline

#177 2021-04-03 11:41:19

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

List of things for a business:

Target mass delivery to surface for design envelope that shell can contain plus its cost
Number of delivery to get to desired levels of materials mass for project requirement ex. concrete pad build
Launch system capability to achieve mass delivery towards the destination cost
Launch cycle count for cost to achieve goal of project for mass delivery
Cargo materials cost for project
Integration costs of materials into shipping containers shell

Markup of business model to make a profit.

Offline

#178 2021-04-03 13:55:56

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,335
Website

Re: Ballistic Delivery of Supplies to Mars

I would point out a minor (but important) point.  If you elect for a direct entry and landing,  there is NO delta-vee burn required!  You simply hit the atmosphere above Mars escape speed and dissipate that kinetic energy as aerobraking drag at hypersonic speeds.  The same thing is true returning from Mars to Earth,  it's just a higher velocity at entry interface.

That leaves only a fairly minor final braking touchdown burn for a soft landing.  But it does impose an extremely-strict requirement for an orbital approach that essentially grazes the planet tangentially,  absolutely NOT hitting it dead-on!  They call that an "entry window",  but that very shallow entry angle is exactly what it really amounts to.  It's in the 1-2 degree below local horizontal range.

THAT is how you increase the braking path length from about a hundred km to thousands of km!  And THAT is how you achieve deceleration from interplanetary speeds to ordinary supersonic speeds,  all in air thin enough to survive the friction heating rates!  The "thin air" for such deceleration on Mars exists from an entry interface altitude of around 135 km all the way down to the surface,  essentially. 

The same "thin air" deceleration region at Earth exists from an entry interface altitude of around 140 km,  down to around 33-35 km altitudes.  Below that somewhat-fuzzy lower boundary,  both the heating rates and the wind pressures are just too high to be survivable with anything we currently know how to do,  if entry occurs at interplanetary (above-escape) speeds.  Warheads were suborbital,  and could enter far steeper (nearer 45 degrees below horizontal).

You only incur an arrival delta-vee if you decelerate into orbit.  That is true off Hohmann transfer,  or any of the faster conventional ellipse transfers with shorter flight times and higher departure delta-vees.  The so-called "ballistic capture" we have recently been discussing offers a way to avoid much (?) of the entering-orbit delta-vee.  That consideration DOES NOT apply to direct entry. 

Whether there is really a dramatic savings with "ballistic capture" into orbit is open to argument,  since the capture orbit is a very high-altitude elliptic orbit of significant eccentricity.  It costs significant delta-vee to bring that down to something actually useful.  That kind of orbital mechanics I understand very well,  and I can actually do it. 

There is NO savings with "ballistic capture" if you elect for direct entry. 

GW

Last edited by GW Johnson (2021-04-03 14:24:56)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#179 2021-04-03 17:49:04

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For GW Johnson re long, gentle descent for packages intended for ballistic delivery.

Your arguments in favor of a gradual atmospheric slowing for delivery of non-perishable supplies to Mars have persuaded ** me ** (for sure), so I'd like to invite your advice on a refinement of the method.

Packages are likely to arrive with a variety of velocities with respect to Mars, and they will not all have the ideal trajectory with respect to the customer delivery site.  So here is my question:

Can you imagine the arriving heat shield saucer shaped package being able to "sail" the atmosphere in order to deliver itself to the needed destination?

As I understand it, the Perseverance delivery package was able to adjust it's course to some extent, although I would imagine the flight engineers did everything they could to insure the vehicle was on precisely the right trajectory so that as little adjustment as possible was necessary.

Going forward, can you imagine flight engineers and vehicle designers able to plan for significant adjustments in trajectory by the arriving vehicle, so as to be able to widen the range of possible approaches while retaining the precision needed for customer delivery to needed locations, and avoiding departure from optimum to endanger humans on the planet or place property at risk?

The X-37b vehicles operate entirely autonomously (as I understand it).  That is a model for the kind of vehicle I'm talking about.

(th)

Offline

#180 2021-04-03 18:49:29

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

The sensors for perseverance.
https://mars.nasa.gov/news/8903/sensors … severance/

MEDLI2 was one of the crucial technologies onboard the rover’s protective aero-shell that helped document the entry, descent, and landing of the spacecraft.

heatshield side with sensors
8903_medli2-on-heat-shield-1200.jpg


top of the back shell
1024_Illustration_of_Mars_2020_entry_vehicle_arriving_at_Mars.jpeg

to aid or control the slope of the landing profile the back shell mass.

Eventually, the vehicle ejected six tungsten ballast masses to allow the vehicle to better align itself for deployment of its supersonic parachute.

the dynamics of the shape and heating of mars entry
1025_illustration_of_data_from_MEDLI2_.jpeg

Offline

#181 2021-04-03 19:11:10

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For SpaceNut re #180 .... thanks for the link to the article (8903) and for the images of the descent!

(th)

Offline

#182 2021-04-04 09:02:50

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

The delta v required for missions
dvchart2.jpg


repost for the topic

The main issue for ballistic is site chosen for landing is how large the site will be as they have been kilometer ellipses, how often are the interval between landings and how long will the site take to cleanup between them of which it is assumed it will vary depending on cargo type, damage to the container ect.

here is that targeting of zone currently with the last 4  missions of Nasa
25490_2a-Ellipse-Map_v3_FullAnnotation-web.jpg
https://mars.nasa.gov/resources/25490/z … he-target/

Of course that was with the dreaded parachutes being used....

Offline

#183 2021-04-04 10:03:31

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,335
Website

Re: Ballistic Delivery of Supplies to Mars

TH ref 179 above,  "sail" the atmosphere question:  we have long done exactly that,  since Gemini in the mid 1960's. 

The amount of turning you can get depends upon the max side force to drag force ratio you can achieve,  and that depends upon the shape of the entering body.  It is only available as an effective item during the hypersonics,  where the aerodynamics forces far exceed the weight force. 

Blunt capsules have a peak force ratio on the order of 0.1 or less.  The more it looks like an airplane (space shuttle or X-37b),  the higher that number can be,  perhaps near or slightly above 0.5.  In no case is it sufficient to turn a steeply-entering trajectory into a survivable shallowly-entering trajectory.

I would point out that this effect is inherent to the entry designs for Spacex's Starship at Earth,  and at Mars.  It's in the simulations they have shown at times to the public. Early in the entry,  where speeds are comparable to escape,  the 60 degree angle of attack (between body axis and wind vector) is oriented to lift downward.  The downlift helps prevent bouncing off the atmosphere.  Later in the hypersonics,  the lift vector is upward, once velocity is comparable to,  or under,  orbit speed.  The uplift keeps the trajectory from bending downward too quickly.  This flattens and extends the ride.  Only once out of hypersonics do the two simulations (Earth and Mars) differ,  and quite strongly.

That same lift control was used on Gemini and Apollo,  and by Space Shuttle,  and now X-37b. I think Dragon uses it,  based on the asymmetries of the burn patterns along the lateral sides.  No doubt CST and Orion will use it. 

GW

Last edited by GW Johnson (2021-04-04 10:05:59)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#184 2021-04-04 11:28:44

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For GW Johnson re #183

In thinking about your post, with it's reminder of many space craft developed over recent decades, and trying to put all of that experience into the context of this topic, which is about setting up a successful, long term multiple participant business activity in the Earth/Mars trade, the image of the Space Shuttle stands out.

A (quite reasonable) objection to the current vision for Ballistic Delivery is that the carrier necessarily lands (abruptly) along with the payload.

This entire topic arose from the (often fevered by his own reports) brow of Void.

In one of his visions (preserved in the archive) Void suggested opening a door in the landing vehicle and dumping the non-perishable payload out in order to lighten the load for the vehicle, and thus consume less propellant for the perishable payload.

The US and ** all ** major military organization of ** lots ** of experience opening doors in the fuselage to release payloads.

Given your advice that a certain amount of control over flight path is possible in the hypersonic state, and given the urgency of very ** very ** precise placement of payloads on the surface, I created a mental picture (complete with motion) of an X37b-like vehicle delivering non-perishable items to the surface and then accelerating back to orbit.

That would make strafing runs during various stages of human history look like small potatoes, I admit, but still ...

Can you imagine a future in which something like ** that ** is possible?

We are still let with the problem of slowing to (about) 500 mph per Calliban's advice, and I have difficulty imagining the X37b-like vehicle about to slow-fly at such a velocity, but I don't have access to the modeling software that could answer the question for Mars.

Success in finding a solution along these lines would ** definitely ** improve the business case!

(th)

Offline

#185 2021-04-04 11:42:10

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

In one of his visions (preserved in the archive) Void suggested opening a door in the landing vehicle and dumping the non-perishable payload out in order to lighten the load for the vehicle, and thus consume less propellant for the perishable payload.

Void's Mars Starship Belly Flop Cargo Drop

A means to soft deliver and lessen need for concrete pad

Offline

#186 2021-04-04 12:10:41

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For SpaceNut re #185

Thanks for finding that reference to Void's creative thinking, and adding it to this topic!

On my way back to resume work on the program (ref Housekeeping) I stopped in my tracks with the thought that flowed from the vision of an X37b-like vehicle dropping off non-perishable supplies and returning to orbit.

**That** caused me to remember Phobos .... In the past, GW Johnson has reminded forum readers of the velocity of Phobos with respect to the surface of Mars, and the (fact as I recall the presentation) that there is NOT a significant advantage to stopping at Phobos.

However, if the X37b-like vehicle imagined in Post #184 is possible in the Mars package delivery context, then a flight from Phobos with ** return ** to Phobos would (presumably) be not only possible but practical. 

In other words, even if a vehicle slows to Calliban's recommended 500 mph before dropping the non-perishable payload, the momentum of the vehicle, combined with rotation of the planet ** might ** provide the capability of returning to orbit with fuel and oxidizer carried in the vehicle.

What I'm looking for here (as always) is the very lowest possible cost for delivery of non-perishable goods to customers on Mars, and at the same time avoiding unnecessary risk such as would necessarily occur with a ballistic delivery direct from Earth.

(th)

Offline

#187 2021-04-05 05:29:04

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

Following up on post #186

In the scenario where a payload is dropped off precisely where it is needed by an automated vehicle (such as the X37b) that then returns to orbit, there is a refinement that (I'm hoping) will be within the scope of the topic.

The payload package could include a small solid fuel rocket designed to decelerate ** just ** the payload package, to bring it's forward momentum below whatever the minimum survival velocity may be for that particular material.   A block of highly refined Nickel may not require much care, but on the other hand, a bushel of corn seed may need some velocity adjustment.

The solid rocket motor would have the additional responsibility to sustain the precision of delivery, so it would necessarily include electronics to control the operation of the thruster.  Happily, the rocket velocity adjustment package might well be survivable, and thus re-usable, when it is carried back up to orbit in a traditional vehicle.

(th)

Offline

#188 2021-04-05 18:24:28

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

There is no fuel tanks onboard the x37 and what it does make use of is nitrogen jets from what I remember to do fine movement.
A lifting body is what the back shell does for the current robotic missions to mars less wings.

Also voids idea of going back to orbit leaves a starship in orbit with no means to go anywhere as even if it has enough fuel onboard its not going home once there.

Offline

#189 2021-04-05 18:55:24

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For SpaceNut re #188

Thanks for continuing development of this important (to me for sure) topic!

There ** must ** be fuel tanks on board the X37b!  It routinely performs orbit plane changes. Those require copious amounts of fuel.

Thanks for the reminder of Void's original idea.  I've tried to build on it by suggesting using Phobos as a base of operations.  The ship would depart from Phobos, drop toward Mars and drop off the payload at precisely the right location, and then return to Phobos.  Supply of fuel and oxidizer for the vehicle would (presumably) come from Mars on a tanker designed for that specific duty, much as the tankers in the Starship fleet would be dedicated designs.

Here is a hint of what the X37b may have in the way of tankage:


https://www.colorado.edu/faculty/kantha … ohnson.pdf

Figure 1: 2003 NASA design for X-37 (Courtesy NASA Marshall Space Flight Center 2003) 3.4.2 USAF X-37BUnlike the NASA X-37 plans from 2003, the final USAF X-37B has been widely cited to use a single Rocketdyne AR-2/3 engine using high concentration (85% or higher) H2O2/JP-8 (kerosene) propellants. Table 1: X-37B Dimensions (Courtesy of Boeing)A widely dispersed diagram of the Air Force X-37B featuring a single AR-2/3 engine and fuel and oxidizer split fore and aft of the payload bay, respectively was included in many news articles on the X-37B but could not be verified with official documents. In both the case of tanks split by the payload bay and both located aft of the payload bay the totalpropellant volume appears approximately the same as the payload bay volume, or conservatively ~2m3.

(th)

Offline

#190 2021-04-07 10:36:49

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

This is a follow up on Post #189

The idea of adapting the military strafing run concept for delivery of supplies to Mars from X37b type ships that return to orbit immediately after dropping off the payload led to a recollection of kbd512's suggestion of magnetic launchers.  While magnetic launchers are (so far) limited to aircraft departing an aircraft carrier, they do hint at what may be possible.

At first I imagined a magnetic track able to accelerate a pod (fitted with a hopper) to the velocity of the X37b-type ship, accepting the payload, and then decelerating by feeding energy back into the supply line.  A one ton payload would contain kinetic energy, and (presumably) that energy could be captured and saved instead of just lost as heat.

However, there ** is ** a variation of this idea that does not require invention of technology, as is the case with the magnetic track.

That would be a simple electric car on a traditional two rail track.  The car would accelerate to match the velocity of the X37b-type vehicle, accept the payload, and then decelerate by simply coasting until momentum is low enough to tolerate mild braking.

The car would then reverse course and deliver the payload back to the starting point.

At this point, the mass expenditure would be limited to fuel and oxidizer on the X37b-like craft.

Edit#1: this is a carry over from the Dry Ice Pneumatic Tool topic .... Acceleration of the receiving cart in a deceleration track for non-perishable payloads might be performed by a pneumatic process.

(th)

Offline

#191 2021-04-07 18:21:13

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

GW would be more able to answer if the ship had all fuel to make use of for whether it can get back to orbit since its slowed down so much from the 3km ish altitude but I suspect that it can not.

http://www.astronautix.com/a/ar2-3.html

Rocketdyne h2o2/kerosene rocket engine. Future-X Demonstrator Engine. Gas generator, pump-fed. Heritage technology in evaluation for current applications. X-37 Reusable Upper Stage Vehicle. Date: 1999. Thrust: 29.34 kN (6,596 lbf). Specific impulse: 245

https://en.wikipedia.org/wiki/X-37B

The X-37 for NASA was to be powered by one Aerojet AR2-3 engine using storable propellants, providing thrust of 6,600 pounds-force (29.4 kN).

Offline

#192 2021-04-07 20:00:20

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,335
Website

Re: Ballistic Delivery of Supplies to Mars

Mars surface escape velocity is listed as 5.03 km/s.  The surface circular velocity is that divided by the square root of two,  or 3.557 km/s.  I use the surface circular value to get a combination of both the KE effect,  and the PE effect,  on the required ideal delta-vee. 

What that means is,  for a craft dropping from low Mars orbit into the atmosphere to deliver payload out the door while still flying,  your ideal delta-vee back from drop to low orbit is some 3.557-0.450 km/s,  if you choose to make your drop at 450 m/s flight speed.  That's 3.107 km/s utter-minimum-required ideal delta-vee. 

I typically use 5% drag loss and 5% gravity loss to surface circular orbit speed here on Earth,  and it gives very realistic-looking numbers.  Mars has weaker gravity at 0.384 gee,  and lower surface density at 0.70% that of Earth.  I typically scale the Earth losses by those values:  1.92% gravity loss,  and 0.035% drag loss.  That is a factor of 1 + .0192 + .00035 = 1.01955 ~ 1.02. 

The mass ratio-effective delta-vee is the ideal value times that factor,  or 3.107 km/s * 1.01955 = 3.168 km/s.  Now,  if you believe that your specific impulse is 245 s,  your effective exhaust velocity Vex is Isp * gc,  or in metric units,  245 * 9.80667/1000 = 2.4026 km/s. 

The required mass ratio to make that burn is then MR = exp(MR-eff dV/Vex) = exp(3.168/2.4026) = exp(1.31857) = 3.738.  That's the ignition mass divided by the end-of-burn mass.  It corresponds to a propellant mass fraction of 1 - 1/MR = 0.7325 = 73.25%. 

That kind of propellant mass fraction might actually be achievable.  It leaves 26.75% of the ignition mass as the sum of inert mass fraction and any remaining "payload" fraction,  such as the propellant for any other burns at all.

OK,  the start of this process is a spaceplane of some kind in low Mars orbit,  that AFTER DROPPING PAYLOAD is still 73-74% propellant mass fraction.  That is not going to be easy to achieve. 

I DID NOT include the deorbit burn in this estimate,  which for low Mars orbit (circular at about 300 km altitude) is near 50 m/s = 0.050 km/s.  Significant,  but not a large effect.  It is the difference between apoapsis speed and circular speed,  for an ellipse with apoapsis at low circular orbit,  and periapsis at the surface.  In other words,  changing to a surface-grazing ellipse.

You will have one hell of a hard time designing a potentially-reusable space plane of inert mass fraction 10% when fully loaded with both propellant and payload.  But if you do,  say this is the weight statement prior to descent from low Mars orbit:  inert 10% + payload 35% + propellant 55% = ignition 100%. 

Ignore the deorbit burn.  Deorbit and drop the payload in the atmosphere without landing,  at some 450 m/s flight velocity and very low altitude.  Now you are the same 10% inert + 55% propellant = 65% at ascent ignition.  Rescaling to make ascent ignition 100%,  that is 15.4% inert + 84.6% propellant = 100% at ignition.   

It can be done,  but there is not a lot of margin (84% vs 74% propellant fraction).  And there will be little room inside the airframe for much but propellant tanks. 

Why do I say 10% inert is hard to achieve in a reusable airframe?  Because most USAF craft are 50% inert,  and most USN craft are 60% inert (they take a bigger beating landing on carriers).  The X-15 rocket plane was 40% inert.  3 were built,  and made a total of 199 flights.

I think designing to 10% inert is a fool's errand,  if you expect to use this thing more than once (which is a part of what is going wrong with the Starship design in flight test).  But then,  stupid is,  as stupid does.

The same calculation done at a far more realistic 20% inert,  and including an approximation for the deorbit burn:

inert 20% + payload 30% + propellant 50% on-orbit.  MR-eff delta-vee = 3.168 km/s ascent plus 0.050 km/s deorbit = 3.218 km/s.  Isp = 245 s says Vex = 2.4026 km/s.  MR = exp(MR-eff dV/Vex) = 3.8167,  for propellant fraction 0.7380.

For the ascent,  we have 20% inert + maybe 49% propellant = 69% ignition,  rescaled as 29.0% inert + 71.0% propellant = 100% at ignition-for-ascent.  MR = 100/29 = 3.4483.  Effective dV = 2.9741 km/s,  which falls short.  We have to reduce payload.

My computer is dead,  or I would have done this in a spreadsheet.  Time at my wife's machine is restricted.  It's really a two-burn problem at two different mass ratios,  similar to my reverse-engineering studies.  One for the 50 m/s deorbit carrying the payload,  the other for the ascent with no payload.  Please feel free to do what I have done before,  in the spreadsheet.

But you can see the conundrum here.  Make the inert fraction more realistic,  and you very rapidly lose payload capability.  Same conundrum as has been faced since the 1950's.

GW

Last edited by GW Johnson (2021-04-07 20:04:51)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#193 2021-04-08 07:17:56

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For GW Johnson re #192

Thank you for the detailed analysis you've provided of the strafing run scenario!

** SO ** close !!!! But alas, (apparently) No Cigar!

In addition, the 245 estimated ISP for X37b is likely above what can be achieved with CO/O2

From Google we have:

The ISP for CO/ O2 is about 200. Compare that to Methane, with a specific impulse of 299, and you can see it's really not that great.
Use of carbon monoxide as propellant on Mars - Space Exploration ...
space.stackexchange.com › questions › use-of-carbon-monoxide-as-propell...
About Featured Snippets
Carbon Monoxide for fuel on Mars - NASASpaceFlight.com Forum
forum.nasaspaceflight.com › ...

***
Regarding the laptop ... I hesitate to suggest this because of previous comments you have published about computer technology ...

However, there are definitely more options than the popular laptop ...

I wouldn't suggest the construction/assembly of your ** own ** build-it-yourself ** desktop if I were not assured of your proven comfort with and successful mastery of a wide variety of mechanical systems.

A build-it-yourself computer is just a mechanical system.  The fluids flowing are electrons, but there is nothing conceptually different from building an internal combustion engine powered vehicle (or rebuilding one, in your case) and putting components together to make a working computer.

I've built many over the years, both in a professional context and for home use.

I **do** own laptops, tablets and other packaged solutions, but these are unmaintainable and have to be discarded when they fail.

On the other hand, a build-it-yourself system can often be teased along well past the expiration date by replacing key components.

It would help if you had a large computer store nearby, but in your descriptions of your surroundings, I've been given the impression such a store is highly unlikely to be anywhere within driving distance.

On the ** other ** hand, modern delivery methods may extend to your area, so it is possible to imagine a mail-order build-your-own system.

The store I find most useful has an outlet in Houston and another in Dallas.

The one in Dallas is 115 miles away, so it could be visited with a day trip.

You can select components online, and have them assembled by staff at the store, but then you trade professional assembly for the "adventure" of learning how to defeat static electricity while assembling components.

The ** main ** advantage of building your own system is the option to transition to Linux, which is supported by multiple non-profit organizations that collectively do an (astonishing to me for sure) job of maintaining the operating system and myriads of support components.

You can (if you prefer) also run Microsoft products on such a machine.  I have systems that all use removable drives, so from one minute to the next a given system could be running Windows 7, Windows 10, Ubuntu (many versions), and other systems with removable drives that can be running earlier Windows, earlier Ubuntu, or even the latest Ubuntu if there is a need, but most of the time there is not.

Much to my annoyance, computer component manufacturers are constantly changing (I suppose **improving** ) hardware, so the removable drives I've depended upon are now replaced by dinky little packages that hold SSD flash drives.  I'm in the process of attempting to make the transition to this "new to me" technology, but I'm definitely doing this only because I have to.

****
Thanks again for the robust analysis of the strafing run scenario!

The results are disappointing, but on the ** other ** hand, due to the preparation of your many earlier posts on the subject of vehicle flight through atmosphere, I do not find them surprising.   Intuitively, I suspected this was a knife-edge scenario, and the balance seems tipped to preclude the possibility.

The original scenarios, of packaging the payload inside the commercial equivalent of the heat shield and back shell of the Perseverance lander seems to have a better chance of success.  I am now leaning toward separating the two (flight package and payload) just before impact to try to improve chances of recovery without unnecessary contamination of one with the other.

Careful design of the flight package may yield valuable materials on the landing site to be salvaged and reused by the customer or by companies set up for the purpose.

(th)

Offline

#194 2021-04-08 19:58:47

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

Well the https://en.wikipedia.org/wiki/Specific_impulse or ISP for a fuel oxidizer mixture to burn in the engines have been shown to be highest for Oxygen and Hydrogen with mixes containing the hydrogen such as methane falling just below them in performance.

Here is an engine fuel chart
https://engineering.purdue.edu/~propuls … quids.html

links at top of this page for the information for each combination
http://braeunig.us/space/comb.htm

As for laptops the one I was using last year when I just checked it was also not function with its keyboard but I have the means to get my data from the hard drive another way which is got to be done....

Offline

#195 2021-04-09 05:54:43

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

For SpaceNut re #194

A USB keyboard will allow you to operate a computer if the only problem is the keyboard.

Likewise, a USB mouse can supplement or replace the mouse pad on a laptop.

***
Thanks for the reminder of the greater ISP of hydrogen and oxygen.

That fuel combination might help with the strafing run calculations done recently by GW Johnson, but I am not holding my breath for a favorable outcome.

It appears that even under the circumstances of lower gravity and less dense atmosphere, a flying delivery is a knife-edge proposition.

However, if it were to turn out that hydrogen and oxygen ** can ** deliver sufficient ISP to make such a delivery method practical, then the next logical step would be to harvest water ice from a passing comet and stock up on Phobos.

***
At this point, for the purposes of maintaining focus for this topic, I am under the impression the most practical approach is to adopt the shape and behavior of the Perseverance lander to reach low velocity (relatively speaking) before the payload is released to land in a designated pit while the delivery package proceeds on to it's designated impact location.  The benefit of this practice is to avoid contaminating the payload with material from the package, and visa versa.

(th)

Offline

#196 2021-04-09 06:05:21

Quaoar
Member
Registered: 2013-12-13
Posts: 591

Re: Ballistic Delivery of Supplies to Mars

GW Johnson wrote:

TH ref 179 above,  "sail" the atmosphere question:  we have long done exactly that,  since Gemini in the mid 1960's. 

The amount of turning you can get depends upon the max side force to drag force ratio you can achieve,  and that depends upon the shape of the entering body.  It is only available as an effective item during the hypersonics,  where the aerodynamics forces far exceed the weight force. 

Blunt capsules have a peak force ratio on the order of 0.1 or less.  The more it looks like an airplane (space shuttle or X-37b),  the higher that number can be,  perhaps near or slightly above 0.5.  In no case is it sufficient to turn a steeply-entering trajectory into a survivable shallowly-entering trajectory.

I would point out that this effect is inherent to the entry designs for Spacex's Starship at Earth,  and at Mars.  It's in the simulations they have shown at times to the public. Early in the entry,  where speeds are comparable to escape,  the 60 degree angle of attack (between body axis and wind vector) is oriented to lift downward.  The downlift helps prevent bouncing off the atmosphere.  Later in the hypersonics,  the lift vector is upward, once velocity is comparable to,  or under,  orbit speed.  The uplift keeps the trajectory from bending downward too quickly.  This flattens and extends the ride.  Only once out of hypersonics do the two simulations (Earth and Mars) differ,  and quite strongly.

That same lift control was used on Gemini and Apollo,  and by Space Shuttle,  and now X-37b. I think Dragon uses it,  based on the asymmetries of the burn patterns along the lateral sides.  No doubt CST and Orion will use it. 

GW


If SpaceX Starship is used for an Earth orbital fly like the old Space Shuttle, would it reenter with the AOA lifting upward?

Last edited by Quaoar (2021-04-09 06:09:47)

Offline

#197 2021-04-09 09:55:14

tahanson43206
Moderator
Registered: 2018-04-27
Posts: 5,597

Re: Ballistic Delivery of Supplies to Mars

Quaoar, you question is certainly an interesting one, and I hope GW Johnson will decide to think about a reply.

However, this topic is devoted EXCLUSIVELY to delivery of packages (non-perishable) goods to Mars!

I understand how easy it is to be distracted by a discussion in one forum that belongs in another.

I also understand that it is natural and normal to ask a question in the topic where the distraction occurred, for fear the poster will not see a question posed in another topic.

We do not currently have a protocol for this situation.

I'll handle it now, but in future, I hope all forum members will adopt a procedure like this:

1) Interesting comment in topic A

2) Member has great idea that belongs in topic B

3) Member asks poster of item 1 to answer question 2 in topic B

Now .. how to choose topic B?

There are a couple of possibilities ... The reference to Starship suggests the best topic might be one about Starship

Pick one, and let GW Johnson know where you would like to see an answer to your question.

In this case, there are 19 topics that contain the word Starship

I'll recommend the first one in the list "Starship is Go" by Louis ... it is popular and has over 1000 posts already.

For GW Johnson, please put your answer to Quaoar in Starship is Go by Louis.

***
For Quaoar ... if the subject of delivery of non-perishable packages to Mars interests you, I invite your contributions to advance the topic.  I am interested in laying fhe foundation for a thriving, competitive business activity delivering non-perishable goods of all kinds to customers on Mars.

There is no reason (that I can think of) why the finest wines, olive oil, and other valuable goods from Italy should not be able to survive the rigors of the planned delivery method.

Any Italian vendor who succeeds with one of these competing services will be able to offer products for far less than the soft landing competitors.

On the other hand, the soft landing competitors will chafe under the glare of competition from the package delivery folks, and will endeavor to lower the cost of their operations.  The consumers will benefit.

(th)

Offline

#198 2021-04-09 12:23:04

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,335
Website

Re: Ballistic Delivery of Supplies to Mars

I did as TH asked.

GW


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#199 2021-04-11 10:42:49

GW Johnson
Member
From: McGregor, Texas USA
Registered: 2011-12-04
Posts: 4,335
Website

Re: Ballistic Delivery of Supplies to Mars

TH:

What I calculated for the "strafing run" delivery in post 192 does not say the notion is impossible.  It is just difficult.  I calculated only for a descent and re-ascent to low Mars orbit.  That begs the question of where will the propellants come from,  if the strafing flight craft is to be used more than once. 

I agree that 245 s Isp is a bit low.  Based on the numbers often cited for the Draco/SuperDraco thrusters on Dragon,  you ought to be able to get just over 300 s in a storable nitrogen tetroxide - monomethyl hydrazine system. That would help.  But the ascent is demanding enough that useful payload fraction will never dominate the craft's weight statement.  It might,  if we could use one or another nuclear rocket notion.

Hmmmm--- I wonder if a surface-to-orbit-and-back transport could be powered by solid core nuclear thermal,  using dirty,  often briny,  Martian water as its propellant?  Might look good payload fraction-wise,  even at only 500-600 s Isp. Done that way,  you might ballistic-capture payloads into that huge ellipse about Mars,  then go get them single stage with a nuke craft. 

The delta-vee would be around Mars escape plus a couple of km/s or so for maneuvers,  and for the landing burn.  Descent would use aerobraking,  then direct propulsive landing.  Call it to be somewhere around 7.5 km/s.  At Isp 500 s,  Vex ~ 4.9 km/s.  Required MR ~ 4.62,  which is not too bad.  That's 78% propellant fraction.  If the inert is 10%,  you have a useful payload fraction ~ 12%.  And that's retrieving stuff from tens of thousands of km above Mars,  not low Mars orbit!

As for the nuclear nay-sayers,  remember that the exhaust is water,  and if NERVA is any guide,  not a whole lot of radioactive debris.  Not many neighbors to annoy,  either. 

Just a passing,  perhaps-out-of-the-box thought.

GW

Last edited by GW Johnson (2021-04-11 10:59:03)


GW Johnson
McGregor,  Texas

"There is nothing as expensive as a dead crew,  especially one dead from a bad management decision"

Offline

#200 2021-04-11 11:02:37

SpaceNut
Administrator
From: New Hampshire
Registered: 2004-07-22
Posts: 21,706

Re: Ballistic Delivery of Supplies to Mars

Right now its a one way mission to deliver a guaranteed payload size for a specific cost.

If a different shape can achieve the payload goal at a lower cost its something that should be looked at.

Currently we have no parachute use and desire to land without retro propulsion for the majority of the payloads as that ups the payload versus fuel engine mass but its not going to work for stuff that needs to be softer landed.

The preciseness of the perseverance landing zone comes into question at this point.

Offline

Board footer

Powered by FluxBB