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Hitchhiking to Moho


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Concept: a lightweight capsule for 4 is a) hurled toward Moho from Kerbin by a recyclable injection booster and b) is caught in Moho SOI by a waiting receiver.  This, in order to minimize the equipment/mass sent en route.

Stipulations:

  1. The payload is required to be a Hitchhiker containing 4 kerbals.
  2. The origin is Kerbin and the destination is Moho.
  3. A recyclable interplanetary transit injection booster (TIB) may give an unlimited boost to the payload within the Kerbin SOI.
  4. The booster must detach before Kerbin escape and demonstrate its own recapture within the Kerbin SOI (from which it is assumed it would subsequently be retrieved by a separate mission).
  5. The Hitchhiker must effect its own transit corrections to acquire a Moho encounter (Cat II) and capture (CAT I).
  6. It is assumed that equipment (e.g. a host tug) stationed/ready at the destination will retrieve the Hitchhiker and bring it down from high orbit to dock with a Moho space station in LMO.

The participant need only demonstrate 1-5 above, but including the Moho capture (by waiting tug) for a Cat II demonstration.  You may start, fully-fueled, in any stable Kerbin orbit.

Judging is based on lowest mass of the transit vehicle immediately after TIB separationKudos will be lavishly awarded for designs that are gangable (and this may become a separate class).

Categories:

  1. guaranteed Moho capture, then awaiting retrieval for disembarkation/refueling (heavier, easier)
  2. mere Moho encounter, then awaiting capture and retrieval (lighter, harder)

Criterion: "it's the mass and nothing but the mass", of the Hitchhiker vehicle.  Couldn't be simpler.
Participants should supply evidentiary screenshots i) immediately after TIB separation and ii) upon completion of the Moho capture (Cat 1 & 2).

Welcome to the 22nd century.

 

z1sSNEI.png

Mass CAT 1 CAT 2 Gravity Assist
2250   Teilnehmer  
3076   Hotel26  
4550     camajcu
       

 

Edited by Hotel26
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23 hours ago, Hotel26 said:

The booster must detach before Kerbin escape and demonstrate its own recapture within the Kerbin SOI (from which it is assumed it would subsequently be retrieved by a separate mission).

Would it be acceptable to not detach before Kerbin escape but still capture within Kerbin SOI?

I'm thinking of a series of gravity assists Kerbin-Eve-Kerbin-Eve-Moho so I could have it capture on the second Kerbin assist instead, which I think would still fit the spirit of the mission.

23 hours ago, Hotel26 said:

You may start, fully-fueled, in any Kerbin orbit.

This should be more specific. Otherwise I could already be on an escape trajectory since that's technically a Kerbin orbit. Barring that, I could be in a very eccentric elliptical orbit, which practically amounts to the same thing. I would suggest "a Kerbin orbit with no part over 90 km" or whatever limit you choose.

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5 hours ago, camacju said:

Would it be acceptable to not detach before Kerbin escape but still capture within Kerbin SOI?

Yes, as long as you do NOT use the booster to impart any further impetus to the payload after reaching SOI escape.

The sticky detail is, of course, course corrections...

(I've edited this response for brevity and in light of my next post.)

 

5 hours ago, camacju said:

You may start, fully-fueled, in any Kerbin orbit.

Amended to include the word 'stable'.

 

Edited by Hotel26
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Incidentally, I should point out that my strategy for the TIB is to use a super-over-powered EscortFive (5) Rhinos and a TON of fuel: no need to finesse the return, particularly for such a light payload.  It has plenty of capacity for a simple "burn back".

kpm9rJi.png   [Note: old 4x Rhino model depicted]

 

If you find this approach palatable(?), there will be no reason to expand the Stipulations in a complex manner.  What do you think?

Edited by Hotel26
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2 hours ago, Hotel26 said:

That might require a screen shot of all resources open at Kerbin escape and again at payload separation.   Does this sound satisfactory?

Oops, I did some course corrections with the booster and not the payload. However, my margins are far more than enough - I could have done this with the payload as well. I'll post my mission when I wake up, hope that's acceptable

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@Hotel26 Here's my mission. Mass with reusable booster is 7465 kg, mass of just payload is 4550 kg.

jPn2Hh3.png

Entire craft in VAB

zlR87L6.png

Just payload

Cgjf9e2.png

Edited into Kerbin orbit, Mun assists plotted

2JcqiPd.png

Second Mun assist plotted

G8Xsqei.png

Mun flyby

Fv7PCch.png

This Mun assist is carefully tuned to make the sum of my apoapsis and periapsis equal to 3.02 * 10^10 meters, which means I have an intersection with Kerbin plotted six years and five orbits later. I wrote a calculator program that uses Kepler's third law to achieve this.

I also have another Mun assist plotted, to gain some extra velocity because the Kerbin assist alone won't give me any extra energy.

mGTphU9.png

This Mun assist is adjusted to give me an apoapsis and periapsis that sum up to 2.292 * 10^10, which corresponds to another intersection with Kerbin and Mun after 5 orbits and 4 years.

qFnIjqw.png

I get another assist from Mun, giving me a plane change and dropping my orbit below Eve. This gives me an intersection with Eve.

Z03MTiE.png

Booster separation

rpl2qAQ.png

Booster sets up a Mun assist that gives a good aerobraking trajectory.

Qo5nKdL.png

Booster aerobrakes

GlqtAEG.png

Booster is captured in a stable orbit ready to be reused

MeIP4HT.png

I use the Eve encounter to increase my Kerbin relative velocity, which gives me a Kerbin assist that I use to increase Eve relative velocity. I use the remainder of the gravity assist for a plane change, to line up the descending node with Eve with the intersection with the planes of Eve and Moho. I also take care to put this near Moho's apoapsis for a smaller capture burn.

0roShbw.png

I use another Eve assist to drop my orbit and give a plane change, lining up my plane with Moho. This sets up a third Eve encounter in a few orbits.

SdmeX60.png

Setting up Moho encounter at Moho periapsis

2hm9m6T.png

Moho encounter set up with a pretty big plane change but I have lots of margin

hbLAHTh.png

Moho capture

33gna2D.png

Moho orbit

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5 hours ago, camacju said:

Moho orbit

Wonderful job and most illuminative!

I'll certainly create a class also for transfers performed without gravity assists to encourage other entries.  (My current prototype is a whopping 10.997t!)

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Well, I believe I have qualified an entry, technically.  It's initial mass, leaving Kerbin SOI solo, is 3,194 kg.  I present Pod IV:

o8usLPo.png


Furthermore, the final version (shown above) will have only a single PB-X50 xenon tank, reducing its total mass to 3,101 kg for a dV of 968 m/s.

                                                                                                                               

I am not going to post this provisional, CAT 2 entry on the leader board at this time and you will see why, based on the following (click + arrows for slide show):

onb1uQf.png   p4W20g1.png   5WbsvAi.png   ld6W5M0.png   l6kz6r6.png

Slide 4 shows that I elected to accept a very bad starting point (KAC indicating a transfer window but not aligned with Moho's DN).  As a result Slide 5 shows a 19km flyby of Moho at a speed of 7km/s!!  5.9 km/s dV would be required for capture.  I do believe that it should be possible to arrive at Moho from Kerbin apoapsis with considerably lower speed differential[1] (particularly if one tunes for a higher, slower Moho SOI periapsis).

The upshot is that I will make a formal entry with Pod IV when I am confident also that I could plausibly demonstrate the CAT 2 ("asteroid") capture by a waiting vehicle.

In addition, I may elect to take advantage of the 'free' boost from the TIB and use a highly-inclined burn to reduce much of the 7-degree plane change from the get-go.

                                                                                                                               

Here's the part list: Hitchhiker, 1K battery, PB-X50 xenon tank, Okto 1 probe core, Dawn ion engine, 6x solar panels[2], 2 pair of 2.5m docks with separators.  The final items make the module gangable but were jettisoned to go "solo" for this test.

[1] minimum bound 2,335.8 m/s

[2] I gave myself the luxury of 6 of these 1x6 solar panels to potentially fully power the Dawn, but the combination of 1K battery and two of these is enough to give full power for a 300 m/s dV maneuver, which is more than I used in total.  I was particularly proud of the canted configuration of these which align the bank off the prograde radial and I think make it possible to rotate the craft into one of two positions that ensure close to maximum power from all panels.  These panels are only 17.5 kg each, but I figure I can shave 70 kg if required.  Finally, note from slide 5 that only 46 units of xenon gas were consumed in making the rather miniscule course corrections (of the order of 43.4 m/s).

                                                                                                                               

Since I do regard this exercise as a 'design collaboration', if any one wants to proceed with a similar design and make a further improved entry for CAT 2, I would be thrilled to see it!

Edited by Hotel26
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14 hours ago, camacju said:

This Mun assist is carefully tuned to make the sum of my apoapsis and periapsis equal to 3.02 * 10^10 meters, which means I have an intersection with Kerbin plotted six years and five orbits later. I wrote a calculator program that uses Kepler's third law to achieve this.

Penny drops...

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Here's my formal submission of the Pod IV mission.  Pod IV weighed in at 3,076 kg after separation from its Escort Transit Injection Booster.
 

See slides 3 and 4 in the following for Escort TIB burn back result and Pod IV initial mass after separation...

Spoiler

 

The initial transfer injection manuever; separation revealing Escort has 2.75 km/s dV remaining for burn-back; recapture and apoapsis reduced to Mun altitude for recycling/refueling.

Cnd98al.png   AQswSoO.png   BKdE5bZ.png

The Pod IV after release of its "book ends", showing a mass of 3,076 kg; an 84 m/s adjustment to Pe; final lap acquisition of intercept.
ruVyHQR.png   Ox3hzS9.png   HJGNT5b.png

Final course correction being set up for low-periapsis traversal of Moho's surface.
PEGVpdb.png

 

 

 


The following sequence shows highlights of the "fox hunt" at Moho.  Note slides 3 and 7, showing intercept distance and closing speed, arrest and capture with remaining dV of 4 km/s:

Spoiler

The trusty hound dog, Finch, selected for its phenomenal 7.8 km/s dV; inclination alignment maneuver; intercept plotted: 300m with 2 km/s closing speed!

adVwqFr.png   u2CpmhJ.png   WnNStEk.png  

Just before flash-by; caught up!; and arrest.
dYenG0v.png   qRjkchE.png   6qQST2G.png  

Recapture with 4 km/s dV still remaining for further maneuvering.
urfVjjN.png

 

I am submitting this mission under Category 2.

                                                                                                                  

I have to say that chasing down the Pod IV in Moho SOI has been the most thrilling exploit I have ever enjoyed in KSP.  Reason enough!

Edited by Hotel26
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Theoretically category 2 would only require very minimal corrections since you'd just need to coast from Kerbin to Moho. You could do it with an ant engine and a dumpling / oscar-b tank probably.

Category 1 would require less than 1100m/s of dv in the payload - my Moho encounter wasn't quite optimal I think. I'm not sure whether ions or a spark booster would be lighter but for that amount of delta-v it might be close.

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6 hours ago, camacju said:

whether ions or a spark booster would be lighter

Good idea.  I think a single Ant+Oscar would do it.  And dump the extensible solar panels.

2,860 kg with 220 m/s dV.

(You can be sure you'd find me in the line at the space port to purchase a CAT 1 ticket, however!!)

Edited by Hotel26
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On 4/1/2021 at 11:53 AM, Hotel26 said:

The Hitchhiker must effect its own transit corrections to acquire a Moho encounter (Cat II) and capture (CAT I).

Could you please explain what this means?

If I don’t have to do any corrections after TIB separation, can I leave the Hitchhiker Container with no propulsion at all?

Edited by Teilnehmer
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3 hours ago, Teilnehmer said:

If I don’t have to do any corrections after TIB separation, can I leave the Hitchhiker Container with no propulsion at all?

Correct.  If you can plot the transit well enough to get a Moho encounter, without any en route adjustments, that would qualify as a CAT II mission.

Good luck, Brave Sir!

(Don't forget to load your 4 kerbals.  :) )

Edited by Hotel26
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  • 2 weeks later...

Payload: 2 250 kg (Hitchhiker Storage Container — 2 070 kg, 4 kerbals — 45 kg each, no inventory)

TIB: 19 482 kg (wet), 3 160 kg (dry)

Spoiler

 

IHAEyUa.png

iXUy97a.png

From MechJeb, I used only node editor.

 

Edited by Teilnehmer
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1 hour ago, Teilnehmer said:

does my entry meet the rules

Great Nerves of Steel, 22nd Century Rocket Man!!

What a job!?  You have blown the competition out of the water.

You go to the top of the leaderboard with a Cat 2 victory.

You are also being presented with the:

  • Medal for Redocking with Space Stations: Not Required (Red & Blue ribbons for Moho and Kerbin, respectively)
  • Medal for Video Production (including Purple ribbon for tasteful music selection)

The Single Question now remaining is: "can anyone beat you?????".

NO.  No one beats that.  (My prediction.  :))

Молодец, друг мой.

Edited by Hotel26
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It seems that the limit for Cat 2 has been reached.

With some trickery, I suspect that a bare hitch hiker with some flags can complete Cat 1. Basically you put it onto a collision course with Moho, and then lithobrake using the flags for a technically captured orbit.

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On 4/17/2021 at 1:49 PM, Teilnehmer said:

Payload: 2 250 kg (Hitchhiker Storage Container — 2 070 kg, 4 kerbals — 45 kg each, no inventory)

TIB: 19 482 kg (wet), 3 160 kg (dry)

  Reveal hidden contents

 

IHAEyUa.png

iXUy97a.png

From MechJeb, I used only node editor.

 

this is absolutely stunning! I have several questions

do you always get into an elliptical orbit before you perform your transfer burn to another body? ho do you know where to setup the elliptical orbit? If you get the period wrong it could actually cost you more delta v. and how did you align the relative angle so that you only had to burn prograde?

How did you plan the capture maneuver on moho?

Do you mind me showing this this  on reddit?

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3 hours ago, xendelaar said:

do you always get into an elliptical orbit before you perform your transfer burn to another body?

Here, I used elliptical orbits for two purposes:
– splitting a huge burn for efficiency (also, the shorter the final burn is the easier it is to recapture),
– cheap inclination change in Ap.

3 hours ago, xendelaar said:

ho do you know where to setup the elliptical orbit?

– Launch n days before the transfer window.
– Make a node, move it n days ahead, fine tune the node for the transfer.
– Keep pressing the minus-orbit button until the node is less than an orbit ahead.
– Reduce the Δv of the node so that the target orbit is elliptical and the time between its Pe and its Ap is n/2 days.

3 hours ago, xendelaar said:

and how did you align the relative angle so that you only had to burn prograde?

Launch Window Planner shows the Injection Inclination.

3 hours ago, xendelaar said:

How did you plan the capture maneuver on moho?

The same way basically.
– Wait until the Hitchhiker’s Pe is n days ahead.
– Make a node at the Hitchhiker’s AN/DN. (I made the Hitchhiker’s Pe near the equator so the AN/DN is almost at the Pe).
– Set the node’s Δv so that the time between your Pe and Ap is n/4 days (two orbits before the rendezvous).
– During the first elliptical orbit, adjust the inclination and make corrections to fine tune the rendezvous.

 

3 hours ago, xendelaar said:

Do you mind me showing this this  on reddit?

I don’t mind of course.

Edited by Teilnehmer
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4 hours ago, Teilnehmer said:

I selected it by length

Tailor made.  It gets a Purple Ribbon.  You are eligible also now to snapshot the Hitchhiker badge for your signature...  Include the hyperlink to the Original Post, if you so desire.  (See my own in signature below.)

"I still can't fathom how you got only a 1.6 km/s closing speed intercept."  Sheer brilliance.  And your passengers looked so 'happy' the whole way...

5 hours ago, Teilnehmer said:

I don’t mind of course.

Pure gold.

Edited by Hotel26
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