Mars 9 tons at a time.

[scottb50]

Another idea is a multiple section heatshield/solar array. During transit it is tethered to the vehicle and acts as a solar collector, when approaching Mars the vehicle attaches to the collector side and rides the heat shield through aerobraking and into orbit. Once in orbit the vehicle undocks and the heatshield/solar collector goes back to producing electricity.<br /><br />Putting landers on the surface would use individual sections, the lander would ride the heatshield through re-entry and detach for landing, the heatshield would use attached engines to return to orbit for re-use.<br /><br />The same principle would work for Earth re-entry. The payload vehicle attaches to the shield, re-enters and makes a normal lander, the shield returns to orbit for re-use. The passenger/cargo vehicle could be fairly simple, a modified business jet or something like SS1. <div class="Discussion_UserSignature"> </div>

 

[j05h]

<i>> Another complication then. Descent path corrections necessary for precise landing generally rely on some amount of L/D and attitude control for steering.</i><br /><br />It's more an assumption than a complication, it just simply needs that type of feature. Leading ballutes have been proposed that have lines or other controls for collapsing parts of the top ring of the ballute, allowing limited aerodynamic control. For landing at a prepared dropzone, it definitely needs steering of some kind. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[thereiwas]

All the fuel necessary to boost the heat shield back into orbit would severely impact cargo capacity.<br /><br />I think it is better economics to just make everything that comes down from orbit useful on the surface. The deflated ballute material could have applications in construction, lining dwellings, or something.

 

[j05h]

<i>> All the fuel necessary to boost the heat shield back into orbit would severely impact cargo capacity. </i><br /><br />Scott is talking about 2-4Km/sec of delta-V, which is substantial. Like, more than the payload's mass substantial.<br /><br /><i>> I think it is better economics to just make everything that comes down from orbit useful on the surface. The deflated ballute material could have applications in construction, lining dwellings, or something.</i><br /><br />Surface use is essential, this is part of why I want to optimize the EDL peripherals and bring it all down in one piece. Ballutes and chutes can be used as suggested, or as dividers indoors, or as "straw" in Mars-bricks. Heat shields and other pallet parts could be recycled as stands for other hardware (like feet for tankage, solar panels, etc) and as porches for EVA and rover storage. The first stage to keeping it dust free might be to keep it out of the dust.<br /><br />One suggestion would be a guide pole or something inside the heatshield/airbag area, that would guide the payload back down onto the HS at ground contact. The HS could also be designed with a crumple zone. Ideally, the payload frame would automatically lock back down, but is mechanically complex.<br /><br />One other option for extra mass is to include an electric jack, stack extra mass on top of it, and lift it using solar power, then drop it slowly at night, this could provide limited baseline power. This could be built into an ATHLETE robot crane, too. Stack several heatshields on top of one, raise it up, drop it as power is needed. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[thereiwas]

I've been doodling. This first picture is my idea for a Mars cargo vessel in its en-route "cruise" configuration. Note that the thrusters poke out through the heat shield. This is so they can control the final landing (like Viking) and also they can fire at low thrust during aerobraking to make the shock layer thicker. (I got this idea from a paper titled "Aerobraking and Impact Attenuation", edited by mark Fischer, 1995.) Note there are no landing legs. The hard shell is expected to crumple if necessary, and there could be internal shock absorbers for the cargo. All the internal parts may not be to scale.

 

[MeteorWayne]

There's no point in doodling right now.<br /><br />SDC is image free at this time. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[j05h]

<i>> I've been doodling.</i><br /><br />Thanks for emailing the pic. Similar to what I'm thinking, except that I'd eject the ballute's outer ring to expose retros on the upper flank of the backshell (if any) around the payload. Crumple-zone at the base makes sense. If the lander can make due without holes in the heatshield, it would be preferable. Same goes for the drop-down airbag. My solution is to inject water in front of the heatshield instead of running liquid engines, same effect. I tend to assume we'd be using the same general kind of SRBs as the Pathfinder. Convince me that liquids make more sense in that role.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[thereiwas]

I'll do revisions. I see what you are saying - don't need the big thrusters until <i>after</i> the ballute goes, so they can be above the edge. What exactly did Pathfinder use?<br /><br />The idea of throttled engines came from that 10yr old paper. I'm not wedded to that. But I like the idea of the thrusters being able to fine tune the landing site.<br /><br />For those wondering what this is all about, I'll post pix here if they re-enable uploads within a week. Otherwise I'll use off-site links.

 

[j05h]

Pathfinder (and i'm assuming MER) used 3ft SRBs called RADs, made by Thiokol. Solids produce lots of consistent thrust, quickly. I like the idea of the "vapor barrier" on reentry, too. Whatever works.<br /><br />http://mpfwww.jpl.nasa.gov/MPF/mpf/rad.html<br /><br />Do you have Flickr account? You could post graphics there.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[JonClarke]

remember too that if you land on the surface with your TPS intact it can provide protection against cosmic radiation and the Mars environment. Neither a trivial concerns for the hab. A typical spacecraft stucture including TPS provides ~10 g/cm2 of radiation protection (about half what is needed) without any additional material.<br /><br />Jon<br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[spacenutnewmars]

Speaking of which I believe that you would want to keep the areoshell intact around the inflatable so as to protect it on the way down. SO a slight modification to the usual split shell is in order to keep the shell mostly intact having just the nose area of it eject to allow for the parachutes to exit for deployment.<br /><br />Does anyone know how much room would surround the inflatable to the wall of the aeroshell? Could it be utilized for some cargo?

 

[thereiwas]

I've been reading the Braun and Manning paper again and came up with these criteria:<br /><br />1. Everything has to fit in the launcher shroud. Lets say 5m diameter.<br /><br />2. The max launch mass is 8,000 kg.<br /><br />3. No shedding of dangerous parts allowed on the way down (post re-entry) so they do not damage stuff already on the ground. This means everything heavy stays attached; no dropping the shell and no skycrane.<br /><br />4. Minimize touchdown velocity in both vertical and horizontal directions. This is required if you don't use the MPF/MER beach-ball landing, which we know is not going to scale up to this size. Those had to deal with up to 16 m/s vertical and 22 m/s horizontal, due to the lack of precise low-altitude control from the solid engines.<br /><br />#4 leads to having a <i>controlled</i> descent, which means throttled or pulsed thrusters.<br /><br />Some realizations I came to about the 9-tons-at-a-time project is that this is not a research mission, but an exploratory one. We are not looking to put one lander in a "scientifically interesting" location so much as to put a lot of landers close to each other in a <i>practical</i> location to form a base camp.<br /><br />So I am working on a design that meets these criteria. It employs a 4.5m diameter 70 degree sphere-cone hard shield (same shape as Viking, and well understood in hypersonic behavior), plus an inflatable ballute that expands that shape before re-entry. My goal there is a ballistic constant below 50, to allow reasonable high-altitude deceleration going to higher-elevation sites. Previous missions have been to low altitude (datum - 4km) sites, with betas from 64 to 94. The higher the beta, the lower you have to be before you start to slow down. At low altitude the ballute is released to float away and land somewhere gently while 4(?) thrusters around the rim of the remaining hard shield control the rest of the descent to the ground. It touches down on the shield. <br /><br />Ther

 

[gunsandrockets]

google IRDT

 

[j05h]

Figuring on a 5m launch shroud is fine. It means you can fit real heavy equipment onboard. 8 metric tons is the goal. Your point 3 should be "#1" in some ways - dropping a heatshield on your greenhouse, PV array or Hab is not pleasant. <br /><br />Liquid descent engines (ie. high throttling) would point to methane/LOX or hypergolics. ISRU derived CH4/LOX is going to be the first thing available at Mars, so maybe not for the first missions, but definitely as a system. Hypergolics are reliable and understood. <br /><br />You could use this "Mars Lite" concept to direct-deliver science rovers, but that is just a heavier version of the status-quo. I'd characterize the concept as "infrastructure" even more than exploration. Plenty of exploration would happen, but the goal is to create a product and small town. As you point out, the goal is to select a practical location for the site. Elysium is equatorial, has giga-tons of known water available and large flat swaths to land the hardware. <br /><br />Good work on the heatshield numbers. As a flood plain of the ancient boreal sea, Elysium is right at the datum, so the landing technology does have to decelerate in the upper atmosphere as much as possible.<br /><br />Jim says that parachutes have a minimal impact on deceleration beyond reaching terminal velocity. You should definitely check out IRDT and ARD for great ballute designs that have flown recently. A 20m diameter (8+m radius) ballute isn't a problem. <br /><br />One other point on the landing system. Cruise stage mass wants to be as minimal as possible. Ideally it is incorporated into the heatshield (RCS) and payload (avionics, PV) so that those components can be reused on the surface. Alternatively, any cruise stage hardware could serve as comsats or other orbital platforms after aerobraking. <br /><br />One question about the ballute is whether it would be inflated for a long period to aid in multi-pass aerobraking? The spacecraft only needs to achieve capture orbit on the f <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[j05h]

<i>> Speaking of which I believe that you would want to keep the areoshell intact around the inflatable so as to protect it on the way down. SO a slight modification to the usual split shell is in order to keep the shell mostly intact having just the nose area of it eject to allow for the parachutes to exit for deployment.</i><br /><br />I'm not sure if you are referring to the launch shroud or the Mar's entry vehicle's backshell? Launch shrouds are often attached to the rocket's second stage, so can't get to orbit (and weigh a lot). If you meant the backshell, yes, we are assuming that cargo is delivered in a protected "pallet" configuration with enclosure or as a matching shaped pressurized container. Payloads would be sized to match a common set of Landers.<br /><br /><i>> Does anyone know how much room would surround the inflatable to the wall of the aeroshell? Could it be utilized for some cargo?</i><br /><br />You are referring to the payload as an "inflatable" or the ballute? Payloads would be of several types, not just inflatable Habitats: there'd be power panels, rovers, ISRU, etc. Mars-bound payloads would be packed to the highest mass possible, even if that is just throwing in extra food or another spacesuit. Everything gets reused on/around Mars.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[thereiwas]

I looked at IRDT - they don't seem to have had any successful tests, and have done no further development for several years. Andrews Space has a nice looking design, is that ARD?<br /><br />Jettisoning the cruise stage before re-entry reduces landing mass, but if there is enough margin it could be left on. The trouble is, where to put the landing thrusters? We have previously discussed having them <i>inside</i> the ballute and they get revealed when the ballute disconnects. That way they are not poking out and interfering with the reentry shape and possibly getting damaged. But that is a possibility - then they can be used for initial retro as well.<br /><br />I was going with a design like earlier landers, where the part with the solar panels and cruise motors did not come to the surface. If the cruise motors can <i>be</i> the landing thrusters then I have to rethink that.<br /><br />Turning the cruise stage into a comm relay is interesting. With no ionosphere point-to-point comm is not possible over the horizon without help. The things that land will not be able to find each other if they come down too far apart. The comm satellites can also provide a Global Positioning service. If each landed module contributes its cruise stage to the network of comm satellites, we could be building both infrastructures at once.<br /><br />Getting into orbit first (by aerobraking) spreads the energy absorbtion into two passes - one to slow down to orbit, and the second to land. And you are going much slower when you hit the atmosphere. The Braoun paper says it is a good idea for that reason. If you pick that parking orbit to be the orbit you want for the comm relay you are already in the right place.<br /><br />Even if the "cruise stage" is not actually doing guidance on the way to Mars, maybe it is worth having just for this purpose.<br /><br />I don't see why the ballute could not be le

 

[thereiwas]

The reason the landed packages need to find each other is because they can't work alone. The Sabatier factory needs the ice-miner/water treatment facility, and both need lots of electricity. The construction tractor needs to refuel/recharge itself somewhere.<br /><br />You want the water and Sabatier facilities to have been working for some time when the first humans get there, so they find full water, oxygen, and methane tanks.

 

[j05h]

ARD is my mistake: that was a European capsule test (no ballute). Andrews' proposed capsule is interesting in that it has an off-center heatshield. I thought that IRDT had a successful test a few years ago? <br /><br />Generally a cruise stage makes sense - especially if the component can become comm/GPS satellite at Mars. Current unmanned probe's cruise stages have been fairly "dumb" from what I understand, using the rover's avionics for control and comm. The fewer the engines and stagings, the better. <br /><br />No matter what, this architecture requires relay sats, so I wouldn't discount the cruise stage.<br /><br />Thanks for the cite and backup on multipass aerobraking. It seems like the ballute should just inflate, not be 2-stage, especially if it also needs to eject. <br /><br />On connecting components, especially sabattier reactors, H2O miners and power, my assumption has been that the dozer or rovers are capable of that remotely. The packages land inside a dedicated landing zone, the dozer approaches, connects and drags it to destination. The heatshield should make a decent sledge. Also, Sabattier reactors are surprisingly small. Pioneer Astronautics work (Zubrin's old company) created suitcase sized ISRU that was almost flight-weight and had near-appropriate throughput. They even made one that created gasoline, drop by drop.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[thereiwas]

Yes, my assumption was the dozer finds the modules and drags each one on its skid/shield close together. Then has to hook them up. Bootstrapping problem - the dozer has to get its own energy from somewhere. It also has to find them, but in the early days that could be commanded from Earth, if we can tell where each came down. When more of the comm infrastructure is in place this will be more efficient. <br /><br />Note to self: tow ring on each pallet so the dozer can hook on.<br /><br />A pure 70-degree cone shield may not drag so well, but maybe we can fudge the pointy bit at the bottom so the weight spreads. A 5t tractor can only drag a 5t sled if the tractor has a lot more traction. Tractor could increase its own weight after landing by picking up rocks with arm, carrying its own heat shield, etc. Don't want the sand too deep.

 

[thereiwas]

According to news articles at the time, the Elysium ice is directly south of Elysium Mons. Looks to be mostly -2 to -3 km elevation there. <br /><br />Did the MARSIS radar ever confirm this ice? I can't find any articles much after the original 2005 announcements.

 

[j05h]

go here and type in "elysium"<br /><br />http://www.google.com/mars/<br /><br />There is a Google thumbtack just to the east of the ESA findings that shows the "rafting" ice. The estimated frozen sea is 800x900km and several 10s of meters thick. My question is whether the smooth, rippled, highland area on the eastern area of Elysium is a glacier?<br /><br />j <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[j05h]

The 70 degree sphere-cone would be somewhat easier to drag if it is guaranteed to crumple on landing. Another option is an ATHLETE type robot for moving hardware out of the dropzone, or a trailer for the dozer. <br /><br />The initial dozer should have solar panels, hook-ups for using base power and possibly a fuel cell or RTG. Tow rings are probably needed on everything, unless using the above solutions (and are still needed for backup)<br /><br />My solution for increasing an early tractor/dozer's mass is to have a hopper that it fills with regolith. This allows a 5 ton dozer to take on 10+ tons of ballast. Remounting the heatshield is an interesting possibility, too. The advantage to the hopper is that if the Dozer needs to mass less, it just dumps some ballast. Traction is an issue with anything being planned - witness Opportunity getting stuck last year.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[keermalec]

Very interesting discussion. In order to contribute significantly to this thread, I've been trying to work out the minimum mass of an aeroshell using existing technology numbers.<br /><br />the closest I have gotten to this is Borowski's triconic aeroshel equation which goes like this:<br /><br />Mab = sqrt(Mpl*(-0.55+0.19*Ve) + Ms<br /><br />Where<br /><br />Mab = Aeroshell mass in tons<br />Mpl = payload mass in tons<br />Ve = entry velocity in km/s<br />Ms is structure mass in tons, assumed to be 6 tons for a 47 to 64-ton payload.<br /><br />As Borowski only considers direct re-entry, the entry velocity is equal to the aerobraked delta-v.<br /><br />However, if we were to consider multi-pass aerobraking, the delta-v per aerobraking maneuver would be significantly reduced and the aeroshel should, conceivebly, weigh less.<br /><br />My question is: is Ve actually ENTRY velocity or AEROBRAKED velocity in the Borowski equation? <br /><br />For example: a Hohmann transfer to Mars induces an entry velocity of 5.47 km/s and therefore an aeroshell + structure mass fraction of 19%.<br /><br />If the same ship were to aerobrake to a Mars parking orbit of 250x33793km (1 martian-day orbit) the aerobrake delta-v would be only 2.08 km/s. Plugging this into the equation would reduce my aeroshell mass fraction from 19% to 11%, thereby adding something like 24% to my payload mass!<br /><br /> <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>

 

[thereiwas]

My preliminary calculations, based on a bunch of equations from nasa.gov and other places (but not yet accounting for hypersonic effects) show a 5t lander will reach a terminal velocity of 73 m/s at around 300 m height using a 20m diameter ballute in the shape of a 70-degree cone.<br /><br />Final deceleration to touchdown depends on a lot of factors I don't have: fuel-mass-consumption of delivering a given thrust in kN for a certain number of seconds. Looks like peak thrust in the region of 150 kN may be required starting at 100m, as slowing a 5t vehicle moving 164 mph takes a bit of a shove. The peak can be a lot less if you start using it higher up (like 1000m), but that increases total fuel. Many tradeoffs.

 

[keermalec]

ThereIwas I think your lander mass should be 8 tons. 5tons is the useful payload on the ground, the rest is aeroshell, ballut etc. <div class="Discussion_UserSignature"> <p><em>“An error does not become a mistake until you refuse to correct it.” John F. Kennedy</em></p> </div>