wumpus

How old is asparagus staging?

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While the name "asparagus staging" apparently barely predates KSP, the idea has been around a long time:

Quote

Before continuing it should be pointed out that all staging is not of the tandem type.  The British use wrap-around staging on many of their missiles today.  The Martin Company has investigated lateral staging, where all stages would fire at the same time.  High performance is the expected result.  At all times propellant would be pumped from one of the outer to the inner stages; and when the outer ones emptied, they would drop off.  Not only would higher thrust-to-weight ratios result, but all stages would be ignited before take off.  Professor Crocco of Italy presented a similar plan to the Fourth Congress of the International Astronautical Federation, in 1953.

And obviously it is harder than it looks like in KSP.  The book I am quoting is from 1958 (presumably hastily published after the Sputnik launch).  It is a nifty book I found in my parents old collection: being from 1958 it starts *everything* from first principles, without launching into extremely specialized engineering.  I've looked through some fairly well stocked used bookstores for other Kerbal-type books on rocket science, but haven't seen anything close.

http://www.amazon.com/Space-Flight-Early-thoughts-projections/dp/B0000CK2Z4/ref=sr_1_1?ie=UTF8&qid=1451578393&sr=8-1&keywords=space+flight+by+carsbie+adams

[ps.  Of course it should include trigger warnings for 1950s-type thoughts.]

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I don't see anything in that quote that would imply that they used asparagus staging the way we think of it today - which is to say, a bunch of rockets clumped tightly that drop off two at a time. It sounds like they're just describing a crossfed stage, and "wrap-around" probably doesn't mean to describe asparagus staging.

While we're at it, no one has yet successfully built an orbital launcher that used crossfeeding and lateral staging (though, admittedly, I've never looked into whether non-spacecraft like missiles have used it.)

The rotational force from fuel churning around in a circle as it does with asparagus staging would destabilize any craft in the real world.

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Asparagus staging as we think of it in KSP is two stages of boosters for crossfeed, falcon heavy might use crossfeed in one stage.
You will want to use two boosters as pumping from 3-4 complicates things more than needed it will also make little sense based on TWR as you will use the same design on boosters and core. 

Asparagus staging is easy in KSP it also works very well as the stages have low twr and fuel faction. Building too high was also an major issue in the old versions so it was smarter to take one core stage and put 6 boosters on it and empty them one after each other. After 0.9 I rarely use it with the exception of extreme heavy loads and perhaps 1-2 missions with 1.25 meter parts before I unlock the skipper. 

standard cross-feed with 3.75 meter parts tend to work just as well for +200 ton payloads. 
One issue with very heavy payload and aspargus is that your TWR tend to tapper off too fast. 

Note that back in 1950 aspargus looked as an good idea as the rockets had far worse TWR and they had less experience with complex rocket systems and why keep it stupid :)
 

 

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The "wrap around" method is just the start of the quote.  There really isn't any reason that asparagus have to be circular.  I've switched to doing them as one long line of boosters.  That way is easier to view and attach (in KSP), and only really becomes a problem if you don't fit on the VAB and/or launch pad.  The Martin Company (I'm assuming non-British, it appears to be LA based and some engineers I knew who were part of the Apollo program worked at Martin in Baltimore, MD) appears to have been working on inline rockets and clearly hits the critical points of asparagus staging:

1: All rocket engines fire at once (note that ignition is tricky and this was certainly appreciated even more in 1958)

2: Fuel tanks fuel all remaining engines and are dropped when empty.

But unfortunately, nobody seems to know how to make a good cross-feeding fuel supply.

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10 hours ago, wumpus said:

While the name "asparagus staging" apparently barely predates KSP, the idea has been around a long time:

And obviously it is harder than it looks like in KSP.  The book I am quoting is from 1958 (presumably hastily published after the Sputnik launch).  It is a nifty book I found in my parents old collection: being from 1958 it starts *everything* from first principles, without launching into extremely specialized engineering.  I've looked through some fairly well stocked used bookstores for other Kerbal-type books on rocket science, but haven't seen anything close.

http://www.amazon.com/Space-Flight-Early-thoughts-projections/dp/B0000CK2Z4/ref=sr_1_1?ie=UTF8&qid=1451578393&sr=8-1&keywords=space+flight+by+carsbie+adams

[ps.  Of course it should include trigger warnings for 1950s-type thoughts.]

There are several problems,

1. computer control has to change with the loss of each stage, the angular vectors change as the outside engines.

2. The fuel has to be shutoff only for the outside engines while all engines are powered  and those fuel lines need to separate with the expired nacell. 

3. The fuel in the outside tank is pressurized both for its turbo and for transfer, its level is dropping which means its hydrostatic pressure is falling, while the recieving tank is not. Therefore there is a pressure dynamic between the two tanks that will overpressurize the turbo, the turbo then needs a pressure regulator on it so that  it is getting constant fuel.

My solution to this problem is to use an sfrb of exact duration required as the base of the outside tank. and place an aero lf tank on top of that, its height being above the starting level of the inside tanks it needs less pressure to move up. Since the sfrb's do not gimble gimbling is reserved for the interior engines

The problem with asparagas is that it increases drag by flattening the verticle profile and widening the horizontal profiles. If you want realy great speed after liftoff, then aero tanks and transitions can get across that mach barrier earlier. A mission like new horizons which the launch trajectory is nearly verticle through the atmospere, energy is lost in terms of time spent over the launch pad, so really good sppeds save energy, but require low drag.  If you are launchin a superwide space telescope you might use asparagas cause you have to linger at suborbital velocities for longer periods of time. 

 

Edited by PB666

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the UR-700 rocket concept used a kind of 'simple' asparagus system, which would have not needed additional pumps etc.

the UR-700 lower stages was meant to use common cores - 3 in the middle, in triangles, surrounded by 6 other cores (two of the side boosters for each of the middle ones)

on each pair of side boosters had one side booster fitted with an additionnal fuel tank on top, the other side booster had an additionnal oxidizer tank on top. those additional tanks were only used to refill the core stage oxydizer and fuel tanks (as they were mounted above, they could directly use the rocket acceleration to refill the core tanks (no need for additionnal pumps besides the engine pump - gravity / acceleration could  do the job)) - when the side boosters ran out of fuel and were staged, the core stages were still full thanks to being refilled by the additionnal tanks (additionnal tanks which were dropped at the same time as the side boosters)

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13 hours ago, wumpus said:

While the name "asparagus staging" apparently barely predates KSP, the idea has been around a long time:

And obviously it is harder than it looks like in KSP.  The book I am quoting is from 1958 (presumably hastily published after the Sputnik launch).  It is a nifty book I found in my parents old collection: being from 1958 it starts *everything* from first principles, without launching into extremely specialized engineering.  I've looked through some fairly well stocked used bookstores for other Kerbal-type books on rocket science, but haven't seen anything close.

http://www.amazon.com/Space-Flight-Early-thoughts-projections/dp/B0000CK2Z4/ref=sr_1_1?ie=UTF8&qid=1451578393&sr=8-1&keywords=space+flight+by+carsbie+adams

[ps.  Of course it should include trigger warnings for 1950s-type thoughts.]

I would complain about how stupid Trigger Warnings are, but I have a feeling it's considered politics, so love it.

 

Apparently F*** = love according to this forum.

Edited by fredinno

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I saw this in the "how to play without Asparagus" thread and thought it was too good for just one thread.  The other important thing to take away from this is that to a remarkably high degree, designing a rocket means designing a turbopump (fuel pump).  I think Scott Manley has stated something like 90% of the engineering comes down to the turbopump, but such things vary so wildly that I doubt you will ever find an "official" number.  Just understand that they are by far the most complex part of rocket science and that making your turbopump more complicated is making your rocket more complicated.  And making things complicated is the enemy of doing reliable engineering.

And while someone pointed out that fire engine pumps aren't the same as rocket turbopumps, I think we can understand that making turbopumps working any harder is a bad thing.

 

On 1/1/2016 at 11:33 AM, Geschosskopf said:

My problem with asparagus, and even crossfeed, is that KSP's fuel flow system makes them work way better than they would in real life.  If you take what KSP fuel lines do at face value, that leads to rather silly implications.  For example, there's no limit on the flow rate of KSP fuel lines.  No matter how fast the downstream engine, be it a Spark or a Mammoth, is burning fuel, the line from the upstream tank always delivers fuel at exactly the same rate, so the downstream tank stays completely full until the upstream tank is empty.  That's asking a lot of a small pipe of constant diameter which might be rather long in some extreme situations. :).

But it's asking even more of the fuel pumps.  The fuel line pump has to deliver whatever flow rate the downstream engine needs against a considerable and constantly increasing backpressure caused by the downstream tank remaining full while the upstream tank drains at twice the natural rate.  And it has to keep doing this even down to the last drop of fuel in the upstream tank, all while not interfering with the flow going to the upstream tank's own engine.  That's an amazing pump there, especially because the same small, light unit works for whatever size engines are involved :D

I muse on such things because I'm a firefighter so I pump a lot of fluid through small, flexible, yellow tubes of arbitrary length :D.  This involves dealing with math about water pressure and flow rates so I have some passing familiarity with the subject.  Anyway, I mostly deal with pumps that can move up to 1500 gallons per minute.  With water being about 8.4 pounds / gallon, tha's 12600 pounds per minute being moved.  A pump that can do this is rather large.  It spans the entire width of the big red truck required to move it around and needs several hundred diesel horsepower to spin it.

Then I look at the stats of the F-1 engine's fuel pump:  15,471 gpm of RP-1 and 24811 gpm of LOX for a total weight moved of 340980 pounds per minute.  Even scaled down to KSP size, that's still 3662 combined gpm, and 30998 pounds per minute, both more than twice the capacity of my $400K, 20-ton firetruck.  And that's just 1 engine---the Saturn V had to feed 5 of these at once.  Then if you put such boosters in a KSP asparagus arrangement to lift some monster payload, each tank in the chain would need twice this pumping capacity, one for itself and the other for the fuel line.  Egad!

Of course, the F-1 fuel pump was small and light, and used a gas turbine with 55000 bhp, so was a totally different beast than a fire pump.  However, I still find it illuminating to think of each KSP-sized F-1 analog as needing 2.5 full-size firetrucks just to feed it, and 7.5 firetrucks for every pair in an asparagus arrangement (2.5 in the dlownstream tank, 5 in the upstream tank).  This mental image is enough for me to call BS on KSP fuel lines.

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55 minutes ago, wumpus said:

I saw this in the "how to play without Asparagus" thread and thought it was too good for just one thread.  The other important thing to take away from this is that to a remarkably high degree, designing a rocket means designing a turbopump (fuel pump).  I think Scott Manley has stated something like 90% of the engineering comes down to the turbopump, but such things vary so wildly that I doubt you will ever find an "official" number.  Just understand that they are by far the most complex part of rocket science and that making your turbopump more complicated is making your rocket more complicated.  And making things complicated is the enemy of doing reliable engineering.

And while someone pointed out that fire engine pumps aren't the same as rocket turbopumps, I think we can understand that making turbopumps working any harder is a bad thing.

 

Piping is also a good proportion of the rocket costs too.

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On 12/31/2015 at 8:37 AM, StarManta said:

The rotational force from fuel churning around in a circle as it does with asparagus staging would destabilize any craft in the real world.

 

The fuel decelerating when it exits the fuel line counterbalances the force of the fuel accelerating into the fuel line.  So you only get force when you are filling or draining the fuel line, or if you shut off the pump.  There's a whole thread dedicated to just this one concept in the science forum here, and the consensus there is that while there would be some torque generated at the mentioned specific points in time, the torque wouldn't be continuous and even when present, would be well within the ability of vectoring engines to compensate for.

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On 1/1/2016 at 0:38 AM, fredinno said:

I would complain about how stupid Trigger Warnings are, but I have a feeling it's considered politics, so love it.

 

Apparently F*** = love according to this forum.

I threw that in after looking for the section and noticing a bit about having meals prepared and of course there would be a wife to do it (and a long-winded explanation as to why).  A bit later there was a bit about a proposal that involved finding two 100lb. men for a manned satellite.  One commenter suggested that two 100lb. women would be far easier to find.  He then proceeded to receive plenty of female fanmail for the comment (no idea about hordes of angry short men "ripped off" of finally getting a chance for glory that doesn't involve the Triple Crown).  To be honest, the idea that different times couldn't possibly have different attitudes and people being positively shocked when discovering otherwise goes back more than 30 years (well before anyone thought to warn triggers).  I figured that although the math hasn't changed since the 1950s, the writers certainly have and people might get a bit more than they bargained with for their rocket science reading.  Still I think it is an ideal book for the KSP player.

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