Sign in to follow this  
FinalFan

Stock Mk3 science vessel (amphibious, ISRU)

Recommended Posts

This is my first craft thread, so advice would be welcome if I am in conflict with any conventions. 
LKO stats have been adjusted for 1.8 aero changes (improved performance for this craft). 

Big Plane to Anywhere (figuratively)
https://steamcommunity.com/sharedfiles/filedetails/?id=1875714661
(Nice try, Bill, but I don't think this is what they meant by "long range ISRU craft"...)

BPA 4R


Well, it's been a long time coming.  I'm mainly a rocket guy, but when I do find myself in the Spaceplane Hangar I very easily get obsessed with fiddling with my designs, more so than with the rockets.  Anyway, I think I've finally gotten this to the point where I no longer have to be ashamed to put it in view of the public.  Let me know if I'm wrong! 

BPA Big Plane to Anywhere


If I'm being honest, the series of planes that this is a culmination of probably began life as the concept, "like my first spaceplane, only bigger".  But eventually an actual mission materialized:  to carry a scientific exploration team to Laythe and (almost) anywhere else with a complete science package and ISRU that wouldn't take months to refuel with. 

 

BPA cargo

One development I'm a bit proud of was the realization that I could attach radiator panels to the reaction wheel that was adjacent to both of the drills and the refiner, elegantly taking care of all my core heat xfer needs.  This development allowed me to finally have a truly streamlined airplane, since I had formerly had medium TCSes attached to the exterior.  Two panels and two small TCSes have less than the mass of one of the two medium TCSes, let alone the aerodynamic improvement!  The small TCSes (middle of picture) are for actual part cooling, and aren't necessary, but having at least a little active cooling capability is handy from time to time, e.g. cooling off during a multi-orbit aerocapture.  (The panels are terrible at non-ISRU cooling in general, and the ones on this vessel in particular are nearly useless at it.) 

The construction of this spaceplane does not use offsets at all, nor any part clipping aside from the wings tilting into the nacelles.  This was a design choice. 

Table of Contents: 
Statistics:  immediately below the table of contents
Atmospheric flight characteristcs:  Balance; Lift; Takeoff; Ascent; Reentry; Landing: approach, normal, water, parachute
Vacuum flight characteristics:  Takeoff; Landing
Miscellaneous:  Docking; Adjusting balance; Water landing; Water movement; Design choices
Edit history 
Postscript (action groups)


Statistics: 
Parts:  100
Mass:  111.35 tons (57.15 dry)
Cost:  401.29 kilocredits
Vacuum Delta-V:  4.6k to 4.7k depending on if you have oxidizer or nothing but liquid fuel.  (counting ore tank, since you can refine it into fuel)
Engines:  4xRAPIER, 4xNERV (0.25 TWR on NERVs if the LF/Ox tanks are empty)
Landing gear:  2xLY-60 in rear; LY-60 and LY-35 in front.  (35 for better taxiing and runway takeoff; 60 for rougher terrain and lower takeoff speed)
Mining:  2x large drills, large converter, 2x smallest ore tank, M4435 Narrow Band scanner, Surface scanner (Surface scanner can refine M4435's results)
Science:  all experiments; 4 places to put science in addition to the lab (Cockpit, probe core, 2x storage unit)
Communications/Control:  Communotron 88-88 (normal direct antenna); RA-2 + RC-001S (with one pilot, can control a probe that lacks direct CommNet connection)
Docking:  1.25m only; no RCS.  See Miscellaneous for tips. 
—Airbrakes?:  Yes, 4.  Retract before landing. 
—Parachutes?:  Yes, 6 plus 2 drogues; positioned to be moderately rear-heavy, but this is adjustable via fuel movement.  Enables safe landing in any terrain or water. 
—RTGs?:  Yes, 8; can permanently run lab and SAS at full strength
—Fuel cells?:  Yes, 3; can permanently run drills and refiner at full capacity
RCS?:  Sort of; 6x Vernors under the nose to assist takeoff/landing in airless environments
—How much delta-V is left after making LKO?:  Even a pilot worse than me should reliably get to LKO with 24-2500m/s remaining before the +203 from refining the ore tanks.  My best so far is 2667 (2870) and I seriously doubt this cannot be bested by an actually talented pilot.  Test flight landed on Minmus with 1213 dV remaining.  Also goes direct to Mun. 
—Amphibious?:  Yes:  can land in water on parachutes or aeronautically, and can take off from water (but only below 25% fuel).  See Miscellaneous for details. 

 

BPA minmus


Atmospheric flight characteristics:
Balance:  The center of mass is almost exactly on top of the center of lift both full and empty, in the back half of the rear cargo bay.  (About 16.3m from the front of the 26.8m craft, or about 61% of the way to the back.)  If you want the CoM to move forward after takeoff, you can lock the tank behind the cockpit (this LF should not be needed to make orbit).  This also can help counteract the already mild tendency to nose up at high speed (see below).  See Miscellaneous for a tip about rebalancing the craft. 
Lift:  Tendency to nose up or down while SAS is off is not violent at any speed; very slight down at low speed (<200), a bit up at high speed (300-1000), and very slight up up during final speedrun. 
Takeoff:  Fully loaded, it can be lifted off the runway at 83m/s (lower on rough terrain due to upslopes) on main wheel (100 for smaller wheel).  Consider using the small wheel on runways or flats to gain more speed before liftoff (due to lower angle of attack while on the ground).  Left to its own devices it lifts off at the end of the runway at about 99m/s (112 for smaller wheel). 
Ascent:  After the 1.8 update, it no longer has to stop ascending to break the transonic speed hump.  My flight plan, which may or may not be optimal, is:  Set at 5° above horizon; it will gradually dip a bit to 2-3° but recover by itself.  After going supersonic it will tend to slowly climb in attitude; stay at 5-7° until about 15km altitude, then begin dropping to 2-3° in order to extend final speed run in the 18-22km altitude range.  (If you're feeling lazy, you can just let SAS do its thing all the way to 1000 m/s or so.)  Activate NERVs when RAPIER thrust falls below 200kN.  By the time thrust falls below 60kN you should be around 1500m/s +/-50; switch to rocket mode when jet+NERV acceleration is unacceptably low and aim for the top of the prograde circle (or a little higher or lower, to taste).  When oxidizer runs out, drop to prograde lock; the NERVs should be able to maintain or increase your time to apoapsis. 
Reentry:  It's recommended that fuel be moved foward to the tank behind the cockpit for reentry for extra stability.  For example, in testing, given a 100kmX15km LKO reentry orbit and only 500 units of fuel remaining, a neutrally balanced craft struggled to maintain a 40-45° pitch without using airbrakes, while a craft that moved that same small amount of fuel forward had no trouble.  It should be noted that the balanced craft had no trouble with a 30-35° reentry profile.  1000 units of fuel (~10%) balanced forward is enough for a radial out pitch to stabilize forward instead of flipping out.  Use caution if returning from other celestial bodies; it's not recommended to dig deep into the atmosphere on the first pass without decelerating first. 
Landing approach:  If airbrakes were used, retract prior to landing as the bottom ones may be destroyed otherwise.  Perfect balance and generous control surfaces make it relatively maneuverable for a Mk3 spaceplane.  Since it takes off near empty at 53-60 m/s (on big/small front wheels) the stall speed on low fuel should be similarly low unless I'm mistaken. 
Landing normally:  Try not to touch down at more than 5m/s vertical speed.  The fairly wide rear footprint means it should be pretty stable and modest testing has borne this out. 
Landing in water:  This plane is capable of a safe aeronautic landing in water, which was successfully tested at 25% fuel, but parachutes are recommended for landing in water or very rough terrain. 
Landing on parachutes:  Even heavily loaded with fuel, this vessel can land safely on its complement of parachutes, but use of engines to help soften the landing is encouraged.  The Abort action group opens doors for the parachutes and triggers them. 

Vacuum flight characteristics: 
Takeoff:  Fully loaded and on a flat surface, the Vernors are not quite strong enough to lift the nose for vertical takeoff in Munlike gravity.  Instead, get forward motion and it should be able to lift off shortly with the help of the thrust attitude, especially if the vehicle runs off the top of a hill.  Use of RAPIERs is recommended unless terrain is very flat. 
Landing in vacuumdV can best be conserved by a "reverse takeoff" posture, where final approach retains some horizontal motion while vertical motion is very low, but this is not easy.  It is probably more practical to descend on the engines rocket-style, and then transition to horizontal when near/on the ground (fall on the wheels).  This has been tested on the Mun.  Be careful to keep the plane level (don't let it roll on its side or you may lose a wing).  The Vernors can slow the fall of the front end, but this should not be necessary in Munlike gravity. 

Miscellaneous:   
—Recommended docking procedure with this vessel is as follows:  1. Rendezvous; 2. Make a close approach (50 meters dock-to-dock* or less), then cancel relative motion; 3. Align to the desired docking port, and accelerate a little for final approach.  This technique has been highly successful on larger versions of this vessel docking with still larger vessels.  *(Bear in mind that when approaching tail-first the engines are almost 27m closer to the target than the docking port, and flipping tail-to-nose will bring the docking port of this craft when normally balanced 32 or 33 meters closer to the target due to where the vessel's pivot point is.  A dock-to-dock separation of 50m would mean a real distance facing away of 23m and 17m after flipping). 
—When altering the balance of the craft (e.g. to put the CoM more ahead of the CoL), keep in mind that adding fuel to the rear and front LF tanks in a 2:1 ratio will be approximately neutrally balanced, i.e. will keep or return the ship to close to its starting balance. 
—Water landing (via parachute) was tested on Kerbin at 75% fuel.  If your splashdown attitude is close to vertical, your docking port may be at risk of destruction as you rotate down, but this can be prevented by using the Vernors to slow your fall.  (Presumably similar precautions should be taken if landing on Tylo.) 
—The top speed in water is 38.7 m/s when full.  The top speed on low fuel is uncertain because during testing the plane unintentionally took off.  In subsequent testing, the vessel was able to intentionally lift off when top speed in water was about 70 m/s, when fuel fell to between 20 and 25%.  (Highest speeds were obtained when fuel was moved forward and SAS set to prograde.) 
—Why the precoolers?  Although the shock cones more than meet the needs of normal flight, I like the idea of having strong static airflow for those, ahem, "off prograde" situations.  They are also handsome. 
—Why the everything?  This design was not arrived at minimalistically; I'm sure there is a lot you could cut, starting with the rear parachutes and airbrakes.  But I wanted a feature-rich craft, and those are features, and it is Minmus capable, so there.  Having said that, I do still welcome criticism if you think anything is too blatantly unnecessary. 
—Why no offset?  I just didn't want to use offset; a little bit to neaten up the often messy intersections of aerodynamic parts is okay but I often see it used in a way I think of as exploitative.  So in a way the only minimalistic thing about this design is the offset and part clipping, which was a design choice. 
—After the 1.8 atmospheric changes, this plane can actually fly on a 3R+3N configuration, but taking away two nacelles worth of LF completely negates the benefit.  It's slightly less dV, significantly less TWR, and a more annoying ascent path; why bother?  Well, I could probably just yank one jet off the regular design (keeping 4 NERVs) and limp to orbit, but the dV gain (112 I think) is, while noticeable, quite modest and I would be nervous about sending it to Laythe untested with that much less atmospheric performance. 

So, how do you like the plane?  How do you like the post?  Comments and questions welcome. 

Edit history: 
1.1—9/28/19:  Added vacuum landing notes.  Added "Miscellaneous" section.  Made major changes to vehicle (reduced RAPIERs from 6 to 4, replacing two Mk3 side pods with four Mk1 side pods).  Edited text accordingly.  9/29/19:  Added Minmus picture.  Edits to vacuum landing notes and other things.  9/30/19:  Swapped location of RAPIERs and NERVs (reducing tailstrike risk); minor text edits. 
1.2—10/4/19:  Minor adjustment to front wing AOI and location; small but critical adjustment to rear wheels to eliminate drift on takeoff.  Added location of CoM to "Balance".  Added "Takeoff"; edits to "Ascent" and "Landing Characteristics".)  Finally changed top picture to reflect new version of craft. 
1.3—10/5/19:  Added "Communications"; added more detail to CoM location, "Lift", and "Takeoff"; added RA-2 to vehicle and replaced bottom pair of shock cones with NCS tanks.  (Reduced cost by 3300, increased wet mass by 0.91, dry mass by 0.11, part count by 3) 
1.4—10/10/19:  Updated "Landing in vacuum" to reflect finally testing Mun capability; added "Takeoff in vacuum".  Removed 1 fuel cell (3 remain) in the belief that this was enough for even maximum ore concentrations, subject to review; please let me know if this is found to be wrong.  10/11/19:  Added water landing/movement/takeoff details.  10/13/19:  Added postscript.  10/15/19:  Added table of contents.  Reorganized flight/landing characteristics.  Added detail to docking.  Updated photos (10/5 changes), minor text changes.  10/16/19:  Added "Reentry", minor edit to "Ascent".  10/22/19:  Altered commentary on small TCSes. 10/23/19:  Removed Z-4K battery after finding a way to mount the drills on the reaction wheel and still fit them through the cargo doors.  Added small ore tank for symmetry in new location.  (Cost reduced by 4.2k, mass increased by 0.675t wet but reduced by 0.075 dry.  Battery capacity reduced from 5710 to 1710.)  Updated cargo hold picture.  10/26/19:  updated "Ascent" to reflect 1.8 aerodynamic changes.  Redid Minmus test—new photo. 

Postscript:  the action groups: 
1:  RAPIER toggle (on/off)
2:  NERV toggle (on/off)
3:  RAPIER mode swap & air intake toggle (open/shut)
4:  All cargo bay doors toggle (open/shut) & small thermal control system* toggle (deploy/retract)
5:  --- (nothing)
6:  Drill toggle (deploy/retract)
7:  Surface harvester toggle (on/off)
8:  Fuel cell toggle (on/off)
9:  Obtain all possible science, including crew report
0:  AIRBRAKES toggle (deploy/retract)
Lights:  default (all lights turn on or off)
Landing gear:  default (all landing gear extends or retracts—note that this is NOT a toggle)
Brakes:  default
Abort:  The top cargo doors open and all parachutes deploy.  It's possible that some parachutes won't deploy if the doors aren't already open; just press the button again. 

*(Note:  the interior thermal panels are always on by default)

Edited by FinalFan
Added edit history

Share this post


Link to post
Share on other sites

Seems like you did not discover offset feature. Maybe I'm a bit rude, but no "wow-effect". This craft is not efficient, not cheap, small, huge, realistic and not unique. There are many unnecessary parts such as airbrakes, chutes, mk3 cabin, reaction wheels. How does it supposed to land on airless planet? On tail? How to dock? 

No need to download it, just because almost everyone can create a craft like this. I think you could make it looking better and being more efficient. 

Share this post


Link to post
Share on other sites

I think it looks very nice. And it's not easy to make a big and lumbering mk3 plane which flies reasonably well, especially if you're into rockets.

Share this post


Link to post
Share on other sites
On 9/28/2019 at 6:40 AM, IkranMakto said:

Seems like you did not discover offset feature. Maybe I'm a bit rude, but no "wow-effect". This craft is not efficient, not cheap, small, huge, realistic and not unique. There are many unnecessary parts such as airbrakes, chutes, mk3 cabin, reaction wheels. How does it supposed to land on airless planet? On tail? How to dock? 

No need to download it, just because almost everyone can create a craft like this. I think you could make it looking better and being more efficient. 

Thanks for your feedback.  Although "wow effect" is extremely vague and subjective, I think I know what you mean and I agree that this doesn't have a lot of it.  I also agree that it has a lot of things that a minimalist design would cut away.  This was not intended to be a minimalist design.  I would like to answer your questions, though; and, in turn, I'd like to ask you a few questions. 

A--airless landings:  Indeed, I anticipate going in tail first as that is how I would be decelerating; however, I would plan to land at an angle and hit on the wheels instead of the tailfins.  I sort of thought this was standard practice for spaceplanes but I could add it to my OP if you want.  Does this answer your question? 

A--docking:  You rendezvous, approach the other ship, zero out thrust again, turn nose-on to target docking port, and then accelerate a little and hold steady.  I've docked this way with even larger vessels (on both sides of the equation) and been fine.  (Including a larger, earlier version of this spaceplane, but I wouldn't inflict its handling characteristics on others.) 

Q--Mk.3 cabin:  is the objection that it's heavier, on a ton per kerbal basis, than other command pods and kerbal carriers?  That's true, but it also has a very high heat tolerance and I thought that would be a useful feature for reentry.  Also, I'm not even sure how I could replace it without totally redesigning the plane; I don't think I need another Mk.3-2.5m adapter. 

Q--reaction wheels:  I presume you mean that having three larges and the cabin is unnecessary and I could cut two of the larges and still be okay.  If that's what you meant, then I agree; I believe it made a 180° turn in 25 seconds (after making LKO, so longer full) but I just wanted to be faster in case of having to make fast adjustments on airless landings/takeoffs, since I'm not highly experienced in doing those in vacuum.  However, if you meant that I could cut down to ONE of my four reaction wheels (counting cabin), then I have to disagree as that would be an unacceptably slow turn speed to me. (Note:  While I stand by all of the above for the originally posted craft, the revised craft indeed cut out the two side wheels, being a good 20 tons lighter.) 

Q--"looking better and more efficient":  how would you go about mounting six RAPIERS and four NERVs to a plane with approximately this size and shape?  Considering the weight of the vessel I would be surprised if you could afford to use fewer jets and I would not accept the <0.1 TWR that would result from cutting NERVs.  (Note:  I was indeed able to use fewer jets, dropping LFO.) 

In closing, I agree that this plane would not require all the skill of an expert spaceplane designer.  I myself am not an expert spaceplane designer.  However, I don't think it's quite as easy to slap together as you seem to think.  For example, most people don't seem to remember that radiator panels (as opposed to TCSes) even exist, and they are the key to avoiding the need for medium TCSes which, in order to fit inside the cargo bay, would practically monopolize the science lab's upper surface.  (Or a horde of small TCSes, ditto.)  Also, nothing in the cargo bay uses part clipping, except for a tiny overlap between the materials bay and the perpendicularly mounted probe control (which could be omitted, except I don't have level 3 pilots available to fly it, and others might not also) as well as small parts of the fuel cells in the drills' big main bodies. 

Edited by FinalFan
Struck out obsolete portions (revised craft)

Share this post


Link to post
Share on other sites

From now on I will propose "my own opinion" and not the truth. KSP is the game we love because there are many ways to reach the same target.

So, after this disclaimer I will try to point out what I think could be "different" in your craft and in your post. 

Well then, here we go. The design is subjective as you say, obviously if it looks cool it will be more popular but imo operativity overrides coolness. I like the way you tried to address any issue you could find around with the proper onboard system. The 4250m/s range looks appropriate to reach Minmus for your first pit stop. But we miss a picture of it. You may be aware of the LAW: pic or it didn't happen. Moreover, if I may, "anywhere" is a bold statement and in this case it may look like a clickbait of some sort.

From a "technical" point of view, I think you have too many rapiers and too few nervs. I usually build LF-only spaceplanes to save on dead weight.

My old Ajax 122 had a very similar concept but I had 3 rapiers and 5 nervs. Pics below. (sorry for squatting, but you know, pic or it did not happen :D )

GSAQwVW.png

eP20Izi.png

lYDhp8j.png

Last but not least, there was a thread completely devoted to SSTOs, maybe you could post this craft there instead of giving it a single thread.

Nevertheless I really appreciate the way you tried to explain the decision making process behind the craft. 

Cheers.

EDIT:

precoolers ARE the intakes (at least to me) but sometimes you need just that little extra.

Edited by Signo
precoolers

Share this post


Link to post
Share on other sites
9 hours ago, Signo said:

From now on I will propose "my own opinion" and not the truth. KSP is the game we love because there are many ways to reach the same target.

So, after this disclaimer I will try to point out what I think could be "different" in your craft and in your post. 

Well then, here we go. The design is subjective as you say, obviously if it looks cool it will be more popular but imo operativity overrides coolness. I like the way you tried to address any issue you could find around with the proper onboard system. The 4250m/s range looks appropriate to reach Minmus for your first pit stop. But we miss a picture of it. You may be aware of the LAW: pic or it didn't happen. Moreover, if I may, "anywhere" is a bold statement and in this case it may look like a clickbait of some sort.

From a "technical" point of view, I think you have too many rapiers and too few nervs. I usually build LF-only spaceplanes to save on dead weight.

My old Ajax 122 had a very similar concept but I had 3 rapiers and 5 nervs. Pics below. (sorry for squatting, but you know, pic or it did not happen :D )

[pics]

Last but not least, there was a thread completely devoted to SSTOs, maybe you could post this craft there instead of giving it a single thread.

Nevertheless I really appreciate the way you tried to explain the decision making process behind the craft. 

Cheers.

EDIT:

precoolers ARE the intakes (at least to me) but sometimes you need just that little extra.

Thank you SO much, from the bottom of my heart, for this wonderful feedback.  Firstly, thank you for letting me know whether the overall dV is appropriate (it is, yay!)  Secondly, thank you for warning me that the "anywhere" could annoy people who thought I meant it literally.  It's what I actually named the craft, but I will reconsider that and also think about what else to call the thread regardless of the craft name.  Thirdly, thank you for reminding me that people would like to see a picture of the craft at the promised Minmus.  I have to admit that the version I uploaded was still en route to its first Minmus landing (earlier versions, with medium TCSes had gone there). 

But most of all, thank you for alerting me to the fact that a plane of this size could reasonably fly with that much less engine.  Three RAPIERs, wow!  I think that craft was somewhere in the vicinity of 104 tons based on your picture?  Significantly less than mine, but still—my eyes are opened!  I immediately tried to modify my own, and while the initial test of three RAPIERs failed miserably, four seems to have done the trick.  It handled like a pig on the runway, but it circularized with 2400 m/s left in the tank—without a nosecone!  (I noticed this lack while on my upper-atmospheric speedrun)

As for where to post it, I am a bit confused—I thought individual threads were a common way to debut craft unless it was part of some kind of series or collection.  But I'll look at what you said. 

Edited by FinalFan
Added "where to post" comment

Share this post


Link to post
Share on other sites

The weight at take off was 93.5t, oxidizer was almost absent, I had a few spare for the fuel cells and just in case for that extra TWR burn with rapiers in closed cycle. 

It's been a long time since I've seen the SSTOs topic popping around. I usually went for a K-prize or anything similar and then, depending on the feedback, I used to add the single thread. But that was just my way. And you know what? Useless flying saucers were more popular than crafts you could use during a career game. My flying saucer was "craft of the week" The Ajax maybe got 3 likes.

Beware of the AYYs.

Fu54BLu.png

Share this post


Link to post
Share on other sites
17 minutes ago, Signo said:

The weight at take off was 93.5t, oxidizer was almost absent, I had a few spare for the fuel cells and just in case for that extra TWR burn with rapiers in closed cycle. 

It's been a long time since I've seen the SSTOs topic popping around. I usually went for a K-prize or anything similar and then, depending on the feedback, I used to add the single thread. But that was just my way. And you know what? Useless flying saucers were more popular than crafts you could use during a career game. My flying saucer was "craft of the week" The Ajax maybe got 3 likes.

Beware of the AYYs.

Well, to be fair, I burst out laughing at that flying saucer, so craft of the week wasn't undeserved, lol.  I'd "like" your posts but apparently that feature is currently unavailable.  Thanks again.  The new version is at least as well balanced as the old one, lower stall speed, more dV but less weight, etc.  Sluggish to accelerate after liftoff but somehow still lifts off at similar speed, lol. 

Share this post


Link to post
Share on other sites

NVM about the "like". I am aware I am not @Kasuha  (that was imo among the five best ever, his Jool-5 with a plane was a matter of pure genius) or Scott Manley in the flesh or an airplane scientist like @GoSlash27

We are just midgets on the shoulders of giants.

Share this post


Link to post
Share on other sites
This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this