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bheick
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« Reply #15 on: April 07, 2006, 10:54:21 PM »

Quote from: aftercolumbia
I can't quite get it in my head which way the thrusters are pointed in your renderings...please help me with that (i.e. plumes, or transparent modules, or even just doodles on the current renderings.)  We should put them in modules, the idea being that we can pop them out and inspect them because Crew Ferry is intended to be reusable (and with maintenance via EVA), and Sprint Mars might need the dust cleaned out of them, or other such maintenance as might be required after sitting on Mars for almost four years.  It doesn't have to be implemented in Orbiter as anything removable, it just has to look like it.

The windows...aw...the windows.  I search through my brain to find away to put this politely and my brain fails me so I'll be blunt...they suck.  Don't take it personally though, my drawings suck worse and I haven't put a whole lot of thought into what to do about them anyway...but hopefully that situation will improve this weekend.

The requirements I had in mind for windows were based entirely around the original 3 person Delta Sprint operating in the following modes:

1. Abort configured liftless entry; aerodynamic stability ensures proper pitch/yaw entry attitude is acquired, the roll angle doesn't matter; no windows required.
2. Lift configured entry; end of normal mission with operational electrical and data systems, automatic entry guidance backed up by pilots standing by; accurate visual roll reference required for the aft crew seats (cameras okay).
3. Lift configured entry; end of normal mission with operational electrical and data systems, but malfunctioning or dead guidance.  The pilots are manually controlling entry by following a cue-card roll angle schedule.  Accurate visual roll reference required for aft crew seats (cameras okay).
4. Lift configured entry; end of normal mission with dead electrical and/or data systems.  Pilots controlling craft via manual thruster valve switches operating on emergency power.  Visual roll reference independent of electrical and data systems needed (windows or periscopes.)  Roll angle maintained at zero degrees, therefore descent module will execute a skipping entry that will take it downrange of the normal landing site.  For this case, degredation of entry corridor and directional accuracy is allowed.  Visual roll reference accuracy can therefore be relaxed.
5. Normal landing under parasol; operational electrical, data, guidance, and brake command 3 axis visual reference required for pilots, VOR/ILS, GPS, TACAN radio references may or may not be available.  Forward visibility is needed, a contact line or laser altimeter can be used to time the final flare.
6. Dead parasol; can be caused by electrical, data, brake command, deployment failure, or loss of visual reference needed for controlled parasol landing.  Disconnect parasol and deploy round reserve chute.  Brace for impact...it'll be a rough landing.  The reserve parachute DM attitude is the same as it is for the parasol, perhaps with the nose up a bit higher is okay.  The reserve parachute is either in its own bay forward of the main parasol bay, or is in the same bay as the main parasol, forward of it.  Bheick can decide, but it doesn't have to be modelled for this version anyway.

Lifting entry cases lead to a requirement to have the region from entry interface to peak loads be in daylight for the end of a normal mission, or the pilots won't be able to see the horizon.  This would restrict entries to where the landing zone local time is from somewhat after sunrise to just after sunset.  In a just after sunset case, Case 4 would lead to the pilots losing the horizon after the normal peak loads point.  Hopefully by then the craft will be going slowly enough that roll angle doesn't matter any more (Case 4 is a very desperate and unlikely condition.)  It is likely that the requirement for visual roll reference for entry could be waived after the vehicle's reliability in the normal modes has been proven.  The reason is that putting time-of-day restrictions on entry and landing wreaks havoc on the scheduling for space station crew transfers, and might not be compatible with a Mars Direct ascent rendezvous.

Most visual reference was going to be provided by RocketCams (and at about $150,000 each, might even be cheaper than cutting windows into a 20g entry capable spacecraft!)  Of course, the RocketCams need windows, but these are puny enough to be ignored.  They would be positioned probably near the thruster pods, so the cable and plumbing runs are together, and also so that the plumes can be seen to confirm thruster operation.

The cameras I had planned out were a landing cam, which was put in the front of an airbag compartment and protected by it.  It points down and forward, so you can see where you're going under the parasol.  Another possibility for the landing cam was to put it in the lower thruster pod so that it always worked, and could also be used to assist docking.

The second camera was a centreline docking hatch camera to help with rendezvous and docking.

The third was a nose door mounted camera that looked across the docking port so it could see the docking ring and help guide the last few inches of a docking approach, keeping an eye on such things as alignment and angle, and providing more information on relative positions and motions after docking, but before retracting the dampening rings.

The fourth and fifth were side pointing cameras in the aft thruster pods to provide the emergency roll reference needed.  They are fixed, with really wide angle lenses.  The interface computers put a Sprint referenced HUD over the processed image so that the pilots can quickly find the angle between the horizon and the spacecraft's Y axis (i.e. the roll angle.)  Once rolled over far enough, one will see the sky, while the other will be "in the dirt."  Entry plasma effects (that orange glow) will keep the cameras from seeing the stars and the effect of the horizon blotting them out if entry is at night.  It would also defeat thermograph cameras, which would have otherwise have no problem seeing the horizon at night.

What about real windows?  Only two were needed, the left and right for each pilot, to let them see the horizon should the electrical system or camera data network screw the pooch on the way down.  On Delta Sprint, the pressure envelope went out to the outer mold line and the hatches were next to the pilot seats, so I put the windows in the hatches.  Now, the hatches are further forward and there is a big gap between the pressure cabin next to the pilots and the outer mold line, making "normal" windows impossible.

There are two solutions:

1: A passive periscope, like those used on armoured vehicles.  The outer cover glass would still look like a window, and when I visited airshows with armored vehicles as an Air Cadet, it actually was hard to tell it was a periscope and not an actual window.  This window would have a small appearance on the outer mold line.

2: A recessed window, like they had on the Apollo LM.  This puts a fairly small window in the cabin envelope with a big conical depression around it to the outer mold line so that angular visibility doesn't go down the drain.  The problem with this arrangement is that it would act as a plasma trap during entry, causing localized heating right in front of the window.  Therefore a layer of high grade thermal glass needs to cover the opening at the outer mold line; this glass need not be pressure bearing.  The window in the cabin would be about 200mm wide, while the window in the outer mold line would be about 600mm wide.  In this case, the windows would need to be positioned next to the pilots's heads, so a bit above the "waterline" with the DM horizontal.  The hatches could have little windows too, but being as we don't really "need" to see anything out of them (unlike the pilot's windows), they can be small or absent.

The part I really did not expect were _square_ windows.  The corners of square windows in pressure cabins encourage the formation of fatigue and stress cracks, which is why Yoke Peter and three other de Havilland Comet airliners exploded in 1952.  Nowadays, even the big viewscreen type pilot windows have rounded corners.  The canted posts also discourage crack formation.  SpaceShipOne experimented with oval viewscreen type windows.  I think the windows _really_ need to be round because the craft bears a 14.7psi pressure differential, while the typical airliner bears only 8psi.

Great work bheick, thanks for your help.


I'll go ahead and revise the mesh. Could you provide a draw up of the exterior design that you have in mind to go with your verbal description? That would be gratefully helpful.

It may appear that the windows have squared edges on this un-revised model, but I am aware of the comet, and the metal fatigue incidents in high stress areas with the use of squared windows The comet was a fantastically beautiful aircraft, and it is a shame it had to be a learning experience in aircraft design. The last thing I would want to see is an astronaut getting a surprise when he/she taps on the glass and suddenly thereís an absence of environment. The square appearance is the application of the texture maps black edges over the smooth curves. When rendered, black tends to sharpen smooth corners without set lighting.

About the hatches, that can always be fixed, and quickly too. Your design is almost a mirror image of itís self, so dividing and mirroring the model will easily provide two hatches on both sides if you prefer.

I was holding off on working more on the design until you posted a comment on the previous design, and now that you have, I can continue on a little more with it.

A few things regarding your previous posts:

In the design I donít have much in the way of measurements of the main components, so I could use a few more rough figures of key areas.

I interpreted the RCS in the un-revised model as a system that would be efficient, and provide plenty of torque for maneuvering. Seth took a look at it and we both noticed that that setup was conflicting with the nosecone door, so it was proving to be complicated. I can redesign the RCS easily, that is a piece of cake, but what design for exterior pods do you have in mind? The Apollo SM had 4 sets of unidirectional quads, is that the type of design setup that you would prefer, or something more along the lines of an RCS fixture that is more aerodynamically shaped? Also, I do need a nozzle size, for accuracy and design reasons.

What is the size of the Parasol compartment or the mean volume that the parasol would require to be stored? I havenít modeled that out yet since I donít have the size, just a rough idea of where to put it.
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aftercolumbia
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« Reply #16 on: April 10, 2006, 09:32:57 PM »

Quote
I'll go ahead and revise the mesh. Could you provide a draw up of the exterior design that you have in mind to go with your verbal description? That would be gratefully helpful.


Don't I wish...I'll try to swing that tomorrow, yesterday was slightly nuts.

Part of the reason why I like little oval windows is because this ship goes through some pretty insane stresses and margins.  The pressure margin is 3, vs. 2 for ESAS study, and the structural one is 2, vs. 1.5 (IIRC) for ESAS.  This is to give the best odds for surviving earth ascent failure (i.e. in the Crew Ferry) but probably can be waived for the ERV because it doesn't need to survive Challenger and on Mars there is no point in making it that tough.  That would make it practically easier to put in the aft hatch.

Quote
It may appear that the windows have squared edges on this un-revised model, but I am aware of the comet, and the metal fatigue incidents in high stress areas with the use of squared windows The comet was a fantastically beautiful aircraft, and it is a shame it had to be a learning experience in aircraft design.


You probably don't know then the story of the Avro Canada C102 Jetliner, the second jet airliner ever to leave the ground...losing to the Comet by a mere 13 days.  It has round windows...as a city hopper it would have a lot more fatigue stressing than the Comet, the prototype (alas, the only one ever made, that this excellent plane never went into production is more of a shame) shrugged of a couple thousand demo hours hopping around the States, often with Howard Hughes at the controls.  Avro Canada had a bad habit of seeing too far ahead.  When the more famous CF-105 Arrow was cancelled, they were refining the Arrow (and their secret 730 spyplane) wing leading edges into one that softened the bow shock gradient so that it didn't make an annoying sonic boom.

In the C102 itself, they set up the pressurization system so that as the plane descended, the cabin pressure descent of 200ft/min (normal airliner today, about 350ft/min) didn't wake up sleeping passengers.  These guys were unreal (2nd test flight, landing gear wouldn't come down, so they landed it on the grass, on its nacelles.  It suffered so little damage it looked like it was designed to land that way.)

Quote
The last thing I would want to see is an astronaut getting a surprise when he/she taps on the glass and suddenly thereís an absence of environment. The square appearance is the application of the texture maps black edges over the smooth curves. When rendered, black tends to sharpen smooth corners without set lighting.


I noticed that too.  The windows have rounded corners, but I think given the design loads I anticipate, round would probably still be a lot better.

Quote
About the hatches, that can always be fixed, and quickly too. Your design is almost a mirror image of itís self, so dividing and mirroring the model will easily provide two hatches on both sides if you prefer.


Yeah, that's right.  The only thing that screws up the symetry is the radar in the nose cone.  Thanks.

Quote
I was holding off on working more on the design until you posted a comment on the previous design, and now that you have, I can continue on a little more with it.


Out of time, I'll be back tomorrow
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aftercolumbia
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« Reply #17 on: April 12, 2006, 02:24:56 PM »

Quote from: bheick

In the design I donít have much in the way of measurements of the main components, so I could use a few more rough figures of key areas.


It seems silly now, that I haven't thought of it before.  Delta Sprint's pilot arrangement was anticipated on the "need" for two pilots, and the more esoteric arrangement of the pressure cabin in the first place.  With Sprint and four people, the more cylindrical layout of the cabin, etc.  It makes more sense to put the pilots up front and the windows there too.

A problem that plagues Greenstar and Sprint both is the lack of thermodynamic pressure-volume nformation I have on oxygen, which makes it tough to estimate tank volume and, especially in the case of Greenstar, the needs of the planned vapor pressure curve.  A 0.5m tank between the OML and the pressure cabin would leave 3m of diameter in the pressure cabin, some of which wille be used by structure and insulation.  The "shoulder" diameter of 2.6m should easily be enough to fit two abreast with a control caddy between them.  I'd put about 0.6m of control caddy between the seats in the back, then each seat takes somewhere around 0.6, leaving 0.6m on each side to the outside of the pressure cabin...decent places for batteries and avionics.  A 0.5m diameter spherical tank has about 65L of volume to it.  Assuming that each passenger uses 1L of oxygen per day, one tank would last...16.25...whoa...sixteen days!?  So, two 0.5m O2 spheres is probably overkill.  This means two 0.4m oxygen tanks are plenty.  Then hydrazine at say 0.75kg/L (hydrazine is denser than that at 0.865kg/L or something like that, but we need tank walls, insulation, and an internal bladder)  and we need 110kg...ish, and therefore 147L.  Say if we put that in 4 0.4m tanks for 134L, we'd have 100.5kg.  This leads to a 45.1m/s delta-v, which is plenty for post Service Module separation maneuvering (which amounts to sep rate killing, perhaps one three axis orientation, and a bunch of entry rolls.)

I think the best way to do the hydrazine pressurization for the descent module would be to use simple blowdown, put all the pressurant in the tanks, then the hydrazine system doesn't need separate tanks.  For high fidelity, the thrusters would gradually lose flow rate and Isp as the propellants drain, and because this is proportionately such a small system, so too would the control authority.  Figuring out how it would behave would be a pain, and maybe it isn't worth the trouble.  This is a four year mission and this system will be used for about 2 hours (two entries, the Crew Ferry to the Hab and the ERV capsule entry.)  If you (or whoever is actually writing the code) is willing to go that far, I'd figure it out, AFAL is good enough to do those numbers.

A pair of small GN2 pressurant bottles is still needed for the life support system.  These can go in front of the oxygen tanks, some 0.15m should be plenty.

Quote

I interpreted the RCS in the un-revised model as a system that would be efficient, and provide plenty of torque for maneuvering. Seth took a look at it and we both noticed that that setup was conflicting with the nosecone door, so it was proving to be complicated. I can redesign the RCS easily, that is a piece of cake, but what design for exterior pods do you have in mind?


Well, if you take a look at the Command Module (Apollo analog to the Descent Module for Sprint), you notice it has just a couple of thrusters near the base, and a couple of thrusters near the top, the pods buried under the moldline so you can barely tell that they are there.  I suddenly remember why I made the nose doors open sideways...

Back to the tank layouts at the back for a moment.  The plumbing will have to go around the hatches, obviously, the reason for the over/under layout of the RCS thrusters.  So at the back.  I'll list off the stuff in order going from the top, around one side, to the bottom, as I see it in my head right now.  This is all in the 0.5m gap between the pressure cabin and the outer mold line:

- Parasol compartment (centred on top) and very big; I'd make it about 30deg wide on each side, for 60deg, giving it an inside width around the curve of about 1.57m...make it about 0.6m long, that should give us about 0.47 cubic metres.  The reserve parachute compartment in front, about the same parameters.  Because the Descent Module is narrower and so is the gap between the pressure cabin and the outer mold line, this compartment is a lot smaller.
- 0.4m Hydrazine tank (60 degrees from top)
- 0.4m Oxygen tank (90 degrees from top; on waterline)
- 0.4m Hydrazine tank (120 degrees from top)
- from about 140 degree to about 160 degrees from the bottom should do for the airbag compartment.  This will run a ways forward...as far forward as you think it can go without interfering with anything (first thing I can think of is the ventral thrusters plumbing and wiring runs.)

Quote

 The Apollo SM had 4 sets of unidirectional quads, is that the type of design setup that you would prefer, or something more along the lines of an RCS fixture that is more aerodynamically shaped? Also, I do need a nozzle size, for accuracy and design reasons.


On the Descent Module, I think it will need a total of four pods.  The forward ones are really close to the taper area of the pressure vessel so they'll probably blister.  Because this is the Descent Module, it would need to be aerodynamically faired, for the Service Module, nothing needs to be aerodynamic, but it does need to fit in a 3.75m barrel for the ascent (it is contained within a 4m diameter partial fairing.)

Based on the R-1E, the exit diameters for a 53N thruster would be about 0.12m.  It has three thrusters, one each of left and right.  These are for lateral Y translation with the help of thrusters on the Service Module.  They also provide yaw rotation with the help of thrusters on the Service Module.  They don't need counter thrusters for the Descent Module only configuration.  With the Descent Module on its own, you don't need a countertorquing thruster because you aren't going to be trying to dock to anything with the Descent Module on its own, the translation has little effect on the entry trajectory.  Realistically, they would also provide backup roll, but that need not be implemented in Orbiter.  If it looks like the plume would blast the open nose doors, cant them away from the Y axis (up for dorsal, down for ventral)  That'll hurt their performance in yaw and Y translation just a tad, and their backup roll performance quite a bit more.  This isn't a big deal.

The third points normal to the X-axis...basically straight up for the dorsal pod, and straight down for the ventral pod.  These provide pitch for both the combined vehicle and for the Descent Module on its own.  With the Service Module, a Service Module thruster would provide a counter torque to prevent translation.  These thrusters are also provide assistance for vertical Z translations in the Service Module configuration.  Again, on the Descent Module by itself, it doesn't need a second thruster to counter torque and prevent translation.

For the aft pods, these are tucked in behind the parachutes and airbags and will probably wind up cutting into the knuckle.  This provides the best available moment arm for roll.  Because the OML/pressure cabin gap is deepest here, these can be put flush right into the moldline and don't need blister pods sticking out.

Each of the aft pods will contain three thrusters, similar to the forward ones.  The nozzle openings will probably wind up being a bit bigger and further apart because there is more room back here.  The left/right thrusters are the main roll thrusters.  They always fire two at a time with or without the Service Module.  (The countertorquing thruster is needed to keep the Descent Module from yawing, a very undesirable effect during entry.)  With the Descent Module by itself, we can assume that it's CG is offset just a tad towards the top to form an alpha to generate a bit of lift on entry.  This means that not all translation will be eliminated with the Descent Module by itself, and the lateral Y translation residual will be provided by the dorsal thrusters.  In the reality, the crew configure the Descent Module CG by moving the batteries up.  This will cause a lift vector of somewhere around 0.25 L/D towards the bottom (the crew's feet) for the high energy phase of entry.  The entry attitude is therefore heads down, like it is for Gemini.

The third thruster (in the middle of the three) point forward, but are canted outward quite a bit from the X axis.  These thrusters provide the primary - X translation.  The idea of canting them outward is to keep them from blasting the docking target.

Quote

What is the size of the Parasol compartment or the mean volume that the parasol would require to be stored? I havenít modeled that out yet since I donít have the size, just a rough idea of where to put it.


I havent' figured out the stored size of the parasol, but I can get some rough numbers for how big the deployed parasol is.  It's an orange peel (elliptical) shape loaded to about 400 N/m2 and with an aspect ratio of 7.  It deploys in sections, probably a total of five, like the X-38 parasol did.  This method of reefing the parasol is a lot lighter than a slider and more effective at moderating opening forces.  The drogue acts as the pilot, pulling the bag out of the compartment and then opening it.  The first reefed position will deploy the centre section.  It'll disreef the rest of the sections, one at a time, alternating sides, about once every four seconds.  The whole thing is open in about 24 seconds.

The total area is about 125m2 for about 34m wide by 4.8m long.  I'm expecting an L/D of about 4, and some horizontal speed when it lands, so it'll slide a bit as the airbags collapse.  I'll double check a paragliding handbook to make sure I got the wing loading right.  What I do remember for sure is that this parasol is about as long as a typical one-man paraglider's wing is wide.

I hope that all makes sense...again apologies for not being able to do drawings.
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aftercolumbia
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« Reply #18 on: April 12, 2006, 02:32:07 PM »

The thrusters will wind up in the centerline four squares, and I think wind up a bit bigger than the current ones in your renderings.  The blister fairing will give a bit of clearance above the nose door interface so we won't need a whole lot of cant on the forward lateral thrusters.  I can see how the rendered lateral thrusters would blow the nose cone doors off when they're open.
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bheick
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« Reply #19 on: April 13, 2006, 11:34:45 AM »

I was reading through you post, but I am still a little iffy on the visual.

so...
I grabbed me some pencil, paper, my compass, and me little scale rule and drew up a quick diagram of my interpretation of the RCS location on the CM.



Left is a 90* sectional rotated 45*. To the Right is a top - down simplified.

Since the RCS is a large system in any case, running it on the 45 on all sides and vectoring the thrust from 45* - 90* will provided adequate clearance for both the RCS placements, and the plumbing required for the system.

The only issue would be that forward firing translation thruster. In any case, angling from 25-45* would give it adequate clearance from blowing off the door and damaging and other objects. Moving the thruster back wouldn't hurt since the thruster fires in a vacuum. Also since the thruster nozzle can be angled, the thruster may be placed relatively close to the heat shield where I will not have any impact on the heat durability during re-entry.

Just my interpretation, I could use a hair more information Wink
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bheick
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« Reply #20 on: April 14, 2006, 10:40:27 AM »

Just to put paper to model, here's what I am talking about:

whole object:


Basic RCS Pod Object:
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bheick
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« Reply #21 on: April 14, 2006, 11:10:47 AM »

One more for practical application in the case of the Nose Cone


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aftercolumbia
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« Reply #22 on: April 17, 2006, 01:30:56 PM »

That's great!

I actually had in mind a diamond style configuration in mind with two blister pods over/under at the front and two flush pods over/under at the back.  Perhaps you were thinking of the parachutes...I don't know how long that bay is going to be.

One thing to remember is that the RCS on the descent module isn't really big.  There are a few functions that it integrates with the Service Module so it would be super silly to use the DMRCS on its own supply while the Service Module is still attached, so the SM bypass links (I call them this because they go around the bottom so as not to penetrate the base heatshield, or to do so at the edges.)

This configuration is okay, the translation mode angles suck, but not as bad as I thought they would and for the DMRCS this is a trivial matter.  About the RCS I do have one suggestion that is related to their function, and one that is related to the Payload Escape Stage, which I need to go at length about...I'd kill for a webcam right now!

- the +-yz radial thrusters...the ones that point straight out, it looks like their thrust axis is too close to the CG for effective yaw and pitch control without the SM.  Don't panic though, keep in mind that the CG is pretty far aft, both because it is a big payload for its booster (if the CG is too high, lateral forces caused by wind shears during ascent will snap the adapter or booster's avionics module...and in our case we'd need to consider the Service Module.)  My other suggestion will fix this thrust axis problem.

It's happened a couple times when I've had "exactly something" in mind...and often even doodle down (and suffer from a chronic inability to draw/scan/cam it out and post it here), and what you've produced has turned out to be vastly different...but in every case save the windows, is still plenty good enough.  The RCS is great, so presently I will turf what I had in mind before and "fix" this one:

The blister pods are excellent...maybe even the perfect shape.  They also provide excellent spots to put the Payload Escape Stage (PES; the abort system) rockets.  I call it PES to distinguish it from "normal" abort towers.  These fire during a normal ascent to mitigate their mass so they aren't just deadweight.  The PES has done strange evolution during revisions to date:

- Original Delta Sprint PES was four single motor rocket pods looking much like Ariane 3/4 PAP strap on rockets, put "somewhere" on the Descent Module and eventually found themselves over/under on the hatches for the parachutes and airbags.  I did crunch numbers for the original Delta Sprint PES.
- Sprint/ISTS-M about 8 months ago when I decided to put Sprint on what is now the Greenstar.  The rockets were in the same position, but I decided they should go in better faired pods with two motors in each pod.  Those pods bear an interesting resemblance to your RCS pods, but they were bigger and started behind the hatch line (pretend to draw a circle around the Descent Module in your mesh that barely touches the bottom of the hatches.  It would run just below the lateral thrusters.  That was where the PES fairing nose was.)
- below...

I'll type this up as a set of instructions, but don't take them as obligatory orders, just suggestions.  It might turn out that as you play with the mesh, these turn out to just plain not work and you might come up with something better.

1. Move all the thruster exits forward some...probably about half the diameter of the hatch (0.5m)...the +X axial thrusters should still be okay for the nose doors and the +-yz lateral thrusters will still be okay, and the +-yz radial thrusters will have more leverage for pitch/yaw during post SM separation deorbit coast, and as counterbalance thrusters for the SM integrated pitch/yaw modes.
2. The nose of the PES goes in that nice little chevron shaped notch in the bottom of each pod.  One of the reasons why the thrusters need to be moved is to make room under the outer moldline for the thrust structure between the PES rocket and the pressure cabin (this doesn't have to be in the mesh.)
3. The PES rocket will look like either a little Soyuz or Ariane 5 strap-on, depending on results of some calculations I will shortly do to determine their volumes and masses.  They'll be bigger than the RCS pod.  It might be possible to simply snarf the Shuttle's SRB separation rockets, but I doubt it.
4. PES exit behind the Descent Module's base is okay.
5. The chevron section will wind up being lined with a darker material (probably Inconel or Haynes 230 as part of the thrust structure...funky stuff that can survive the interference heating during entry, remembering that it'll be going base first during this phase of flight.
6. The ERV system does not have a PES, so the chevron tail will probably filleted in to a single point or flat edge...a more boring looking boattail.
7.  There will be one PES rocket under each pod.

I'll do the calculations and put them up in my next post.
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aftercolumbia
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« Reply #23 on: April 17, 2006, 02:25:38 PM »

Payload Escape Stage

Requirement: To accellerate the Descent Module away from a failing booster, imparting about 150m/s over the course of 3-4 seconds (4-5g); this fairly gentle accelleration requirement precludes the Sprint from operating from a solid fuelled booster where shutdown can't be commanded as part of the abort sequence (I don't like the CLV anyway.)  The reason for the gentle requirement is that the PES winds up being onerous to the booster anyway, and during normal firing, imposes thrust loads on the booster's upper stage that come from strange and potentially unexpected directions (design-wise)  Another reason is thrust density and, during normal firing, the severely underexpanded condition of the nozzle will cause the exhaust gases to impinge on the fairing exterior.  This probably becomes a problem at high thrust levels.  It'll look pretty spectacular on NASA TV!

Propellant: solid double-base about 2600m/s exhaust velocity.  The mass numbers come up thus:

1. Abort commanded!!
2. Separated Sprint Descent Module mass w/PES is 5380kg at firing
3. PES fires, at burnout has expended 300kg of propellant, including igniters.  In each of the four rockets, 75kg.  Each rocket has a thrust of 65kN, burnout accelleration is 51.181m/s2
4. The now dry PES rockets are jettisoned at 20kg each, leading to a post-separation mass of 5000kg
5. The Descent Module will immediately swap ends because it likes to fly base first.
6. PES delta-v is 149.2m/s

Volume calculations assume a density of 1.25, a bit on the low side as far as total grain goes, but this one will wind up being multiperforated to get the job done.  This leads to a 60L rocket.

Given a 60cm diameter, a length of 2.4m gives 67.9L, that should be fine.  It'll be about half-on, half-off, CMIIR.

This is what will probably wind up happening during a normal ascent:

1. First stage cuts off, initiating the staging sequence
2. Ballpark estimate of the Falcon 9 second stage is 40000kg, plus a 3000kg Sprint Service Module, 800kg partial fairing, and the above for a total of 49180kg before firing.
3. The total 260kN thrust (which is less than the main engine in this case), causes a final accelleration of 5.287m/s2 and a delta-v of 15.91m/s
4. The main engine of the booster second stage ignites
5. The PES rockets are jettisoned
6. The partial fairing is jettisoned
7. The crowd oohs and aahs Wink

I've made up my mind about the windows...put them between the hatch and the upper RCS pod...not too close to the hatch (closer to the RCS pod is better.)  In the new positions I suggested in the post, this will make the lateral thruster plume very visible...I just hope it doesn't fog up the window.  Come to think of it...the two windows on the top have to stay, the pilots will need to see the parachutes, and it would be a nice gesture that would let them see the parasol during a normal RocketCam(R) controlled descent with their own eyeballs.  (In the event of an electrical pooch screw bad enough to knock out the RocketCams, the electrical motors that run the parasol's brake lines won't work, so they'll have to go to the reserves.  It is also rather unlikely that they'd be able to control the parasol via the windows, and when they can't see forward, there's no point.)

The six forward windows on the current one can go.
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bheick
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« Reply #24 on: April 19, 2006, 09:00:01 AM »

Windows like that above the hatches, or towards the RCS?

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aftercolumbia
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« Reply #25 on: April 24, 2006, 08:53:35 PM »

I suppose, esp. since I have such trouble doing drawings, that I should kinda define some directions:

Forward/aft (in front of/behind) X axis; roll axis:  From the nose to the base; in the vertical position as it sits on the pad up/down (I will try to avoid refering that way and stick with forward/aft.)

Up/down (above/below) Z axis, yaw axis: From the parachutes on top to the airbags underneath.

Left/Right (beside) Y axis; pitch axis:  From...uh...the left side to the right side; +Y is right, -Y is left.

This is how most booster manuals and Space Shuttle by Dennis Jenkins talks...as well as a lot of the "click here to download" documents that most normal people can't understand.

Oh, by the way, I found this fascinating new page.  Click here:

http://www.ibiblio.org/mscorbit.com
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aftercolumbia
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« Reply #26 on: April 24, 2006, 09:03:45 PM »

Hmm...one window on each side of the spacecraft above (+Z) of the hatches, between the hatch and the upper RCS pod on each side.

In that last rendering, uh

                /
              /
           /
          /
        /
      /
  |_

That way...

Dang...I hope you got some imagination...
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bheick
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« Reply #27 on: April 25, 2006, 07:10:46 AM »

Quote from: aftercolumbia
I suppose, esp. since I have such trouble doing drawings, that I should kinda define some directions:

Forward/aft (in front of/behind) X axis; roll axis:  From the nose to the base; in the vertical position as it sits on the pad up/down (I will try to avoid refering that way and stick with forward/aft.)

Up/down (above/below) Z axis, yaw axis: From the parachutes on top to the airbags underneath.

Left/Right (beside) Y axis; pitch axis:  From...uh...the left side to the right side; +Y is right, -Y is left.

This is how most booster manuals and Space Shuttle by Dennis Jenkins talks...as well as a lot of the "click here to download" documents that most normal people can't understand.

Oh, by the way, I found this fascinating new page.  Click here:

http://www.ibiblio.org/mscorbit.com


Yep, I figured you were talking about that, but I was in a hurry last week and did that on the fly.

Well, thatís what you get for working to fast anyhow and not using common sense about which way is up or down.

Oh, and the link is apparently a 404

Quote from: aftercolumbia
Hmm...one window on each side of the spacecraft above (+Z) of the hatches, between the hatch and the upper RCS pod on each side.

In that last rendering, uh

                /
              /
           /
          /
        /
      /
  |_

That way...

Dang...I hope you got some imagination...


Which way you say???, My imagination ran off a while ago when the coffee ran out Wink j/k, I know what direction youíre talking about, and I had that general feeling of ďIím sure, but Iím notĒ. Itís gone now and Iím fairly certain that were on the same page now soÖ


I'll fix 'er up later when I can get a few good free minutes.
I have a good amount of meetings and appointments to go to this week, so I don't have much time to play with currently.

So far I have removed the forward windows as requested, and those side ones and modeled in part of the windows. I have a set location for the parasol compartment finally after dinking around with the upper window placement a bit and shrinking the RCS pods just a little for looks.

I re-made most of the exterior and the nose cone doors to cut down on the triangles, the massive amount of vertices accumulating in certain regions was giving me a headache.

A couple of quick questions while the windows are still on the topic of conversation.
The top windows as you suggested earlier arenít rounded off enough. What I am planning on doing about that is just re-making the windows.

I am going to re-make them as dual sided radius windows with legs that are fixed length, or full radius with a fixed diameter, depending on the area of application. I donít think I am going to make any of them over 30.48cm (12.00in) x 22.86cm (9in).

Hereís a little extra info for you I dug up on glass, the weight. I though you might want it if you needed to calculate the mean dry weight of the craft in total one day.

Weight kg per cu/m
Glass, broken/cullet   1290-1940
Glass, Window-std   2579

Well, enough for now, Iíll get to work on it some time tonight, so I might have a render of a more upright CM before next morning. That one was kind of starting to look like a Frankenstein in a sense with many mixed idea and implementations all in the same project mesh.
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aftercolumbia
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« Reply #28 on: April 30, 2006, 03:53:45 PM »

Quote

Oh, and the link is apparently a 404


I know...it was the 404 page that had me so fascinated Happy

Quote
A couple of quick questions while the windows are still on the topic of conversation.
The top windows as you suggested earlier arenít rounded off enough. What I am planning on doing about that is just re-making the windows.

I am going to re-make them as dual sided radius windows with legs that are fixed length, or full radius with a fixed diameter, depending on the area of application. I donít think I am going to make any of them over 30.48cm (12.00in) x 22.86cm (9in).


That will be fine.  I was expecting 30cm circles but if they can't be that big, we'll have to take what we can get.  Remember the Sprint has a tougher pressure/load bearing job than the rover!

Thanks for the glass info; I thought it was denser than that.  What I'm expecting is that window construction would probably wind up being a laminated pressure bearing pane on the pressure cabin, and an impact strength oriented thermal outer pane with a vented cavity in between.  To fully quantify the "mean dry weight" as you put it, I'd also need the tensile strengths of both glass and laminate materials.  I can easily get those for the 2024 or 2219 aluminum I plan to make the pressure cabin and outer skin from.  My idea for the docking port was to hacksaw a docking port out of a Shuttle and bolt in on...hoping to use a 1575mm standard fixed interface (but I doubt that can be done; it'll probably wind up being a custom interface because the 1575mm probably doesn't have any provisions for pressure sealing...but don't be afraid to use it as a reference...don't try to mesh all those 110 bolts...my computer is too gutless to render something like that!)
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« Reply #29 on: June 08, 2006, 12:10:25 PM »

Little update..


Some assembly required :lol:
http://kimages.be/share/2714831.jpg
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