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Dawn Panther SSTO

Teilnehmer
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Teilnehmer

Teilnehmer

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Dawn Panther SSTO Challenge

VNgBzsp.png

Create a stock craft that…

  • is Kerballed,
  • is single-staged,
  • uses only Panther and Dawn engines for propulsion,
  • is able to reach Kerbin orbit and land back,
  • doesn’t use cheats (in particular, Dawn engine stacking).

Nominations:

  • lowest launch mass,
  • highest launch mass,
  • special prize for originality.
  • Whoever succeeds will be considered a hero.

 

Heroes:

  1. realseek
Edited by Teilnehmer
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JadeOfMaar

JadeOfMaar

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On 4/27/2019 at 1:24 PM, Teilnehmer said:

doesn’t use cheats (in particular, Dawn engine stacking).

I assume that by "stacking" you actually mean clipping: In this case, having a functional part buried within another functional part to simulate a combined effect while visibly saving space.

Have you considered the following? I don't see any hope in this challenge.

Quote

Is this challenge possible?

Many challenges we see are nearly or literally impossible to achieve, and usually very little thought has gone into them, these challenges just annoy people, waste forum space and show that the submitter hasn't really tried.

So test your challenge yourself first to make sure it is possible, you don't have to be successful but you'll soon know if the challenge has a hope of being completed.

 

Edited by JadeOfMaar
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sturmhauke

sturmhauke

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Pretty sure it's impossible as an SSTO. Panthers can't get you high enough for Dawns to start having any significant thrust; meanwhile you have to carry around two different types of heavy fuel. It's probably doable with a staged solution though.

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Pds314

Pds314

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4 hours ago, sturmhauke said:

Pretty sure it's impossible as an SSTO. Panthers can't get you high enough for Dawns to start having any significant thrust; meanwhile you have to carry around two different types of heavy fuel. It's probably doable with a staged solution though.

Did the Dawn get nerfed or something? Last time I checked you could take off from Keverest on Dawns, which is much lower than the Panther ceiling.

Also the Delta-V readout indicates Dawns reach 50% of their peak thrust and ISP at just 46.8 kPa, that's like 4852 meters above sealevel. Forget Panthers, a Rovemax can get you to that altitude.

Edited by Pds314
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Teilnehmer

Teilnehmer

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Dawn gives 1 kN of thrust at 5 km altitude, 1.5 kN at 8 km, and 1.9 kN at 15 km. It’s also no problem to get a high apoapsis with Panthers. From my point of view, the main problem is speed you can get with Panthers.

BTW, I removed the requirement for the craft to be Kerballed.

I’ve also created an alternative challenge where any air-breathing engines are allowed, not just Panthers.

Edited by Teilnehmer
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Pds314

Pds314

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2 hours ago, sturmhauke said:

You could SSTO with ions in older versions apparently, but not recently. @EvermoreAlpaca recently got to orbit with ions, but it was very much not an SSTO.

I just built an airplane that can accelerate beyond Panther limit. Not the most stable thing ever though. Also while it has a generous ~4170 m/s of ion Delta-V, it's just too marginal to get to orbit. At least the way I'm flying it it is.

If it were able to perfectly expend its ion Delta-V to reach orbit, it would be more of an single stage to almost anywhere, with over 2.5 km/s of Delta-V after reaching orbit, but sadly it seems to have serious difficulties getting supersonic without early use of the ions below 12000 meters or so, and climbs very inefficiently. It is however not too much lacking in the raw thrust department, with 64 kN of ion thrust from 32 engines.
2cZw059.png

To be honest I'm kinda tempted to forget dragging a panther up there and just building an ion plane that takes off from Mt. Keverest.

Edited by Pds314
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Pds314

Pds314

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Hmm.... With the current engine config, starting at 6767 meters and then losing a kilometer of altitude tumbling down the cliff is not a good strategy. And it can't go supersonic at under ~18km on its own either.

The question is, would "moat boosters" be an effective strategy or should I try to downscale the ion plane by like a factor of at least 8?

Edited by Pds314
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Laie

Laie

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On 5/1/2019 at 10:38 AM, Pds314 said:

The question is, would "moat boosters" be an effective strategy or should I try to downscale the ion plane by like a factor of at least 8?

I'm afraid the answer is moar boosters.

Last time I seriously dabbled with spaceplanes, a low-TWR approach required lots of wing on an otherwise low-drag vessel in order to keep flying (held up by air under it's wings). This gets easier with increasing altitudes and velocity, where ever more lift would be created from being nearly-orbital. Starting with rapiers and milking them for all they've got, the minimum TWR in nuke-only mode was on the order of 0.2 or so; such a vessel would struggle for a long time with barely noticeable acceleration until it got over the hump.

In this case you need to start your rockets sooner and hence need a higher TWR to just keep flying, Getting a TWR > 0.3 from ions on a vessel that already includes a panther will require several to begin with, and I'm not sure that 0.3 will be enough.

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realseek

realseek

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On 5/2/2019 at 8:38 PM, EvermoreAlpaca said:

While one must always be careful in labeling things impossible, I can say with certainty that I do not see how this is possible.  The TWR just isn't there.

I love finding these "impossible" challanges here in the forum.
Trying to proof somebody wrong is a fine motivation, don't take that away from us, EvermoreAlpaca :sticktongue:

Anyhow, this one is actually possible!
If anybody is still interested in the solution I could upload a video.

The trick is to design for very high L/D at 20km and bounce of the atmosphere multile times while accelerating to orbital speed... Easier said than done :)

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