HLV made from multiple common two-stage cores

[MattJL]

This idea was partially inspired by the "What would a better Saturn V/Lunar Program have looked like?" topic from a few months ago.  It got me thinking about strapping a couple of Saturn 1B-class vehicles (20 t) together to create a 100 t LV.

I've already had an idea similar to this (I can't remember the topic's name exactly, but it was something along the lines of "Saturn 1B with propellant cross-feeding), but that used only the S-IB stage, and not the S-IVB.

So, based off a few (very crude) calculations, five of the common core units, consisting of an 87 foot monolithic (two tanks with a common bulkhead) kerolox first stage and a 50 foot hydrolox second stage, would be attached to one another in a cross shape (four CCUs around a central CCU), as shown in Attachment 1.  The first stage would function as one unit, and separate from the second stage 150 seconds into the flight.

The second stage would also behave as one unit, even though it would be 5 separate CCU upper stages, as shown in Attachment 2.  They would burn out upon reaching orbit, and be capable of delivering 100 t to LEO.

One of these 5 CCU vehicles would also be able to deliver 33 t to TLI.  Orbital insertion would be preformed as with the standard vehicle, but upon reaching parking orbit, remaining propellant (I'm assuming, probably incorrectly, that there would be decent residuals in the tanks after delivering a lighter payload to orbit) would be drained from the outer CCU upper stages to the innermost CCU upper stage, which would have the spacecraft attached to it.  The outer CCUs would then be jettisoned, and the central CCU would preform the TLI burn.

A potential advantage of this vehicle would be flexibility, as it would be able to deliver payloads between 20 t (about as much as the Space Shuttle, IIRC) and 100 t to orbit, without requiring completely different launch vehicles to be built.

Is this idea even remotely plausible?

(If this topic is in an inappropriate place, I'd be more than willing to move it somewhere else.  I wasn't certain if it would be better to put this in the HLV/SLS thread).

[simonbp]

Matt, meet UR-700:

http://www.astronautix.com/lvs/ur700.htm



The best way to launch such a vehicle is cross-feeding, with the engines on the center core drawing from the surrounding cores. When the outer cores are empty, they are ejected and the center core continues on with its own propellant. Doing such a thing with your vehicle would produce a pretty high-performance four-stage vehicle, with lots single-point-failure separation events.

[MattJL]

Oh, my, that thing's quite a monster. 

My only fear with cross-feeding and dropping the outer first stages would be a loss of stability - it'd be one stage pushing five for a brief part of the flight.  That's why I was thinking of letting them function like the Delta IV's CBCs, except they all drop off as one unit.

But now that you mention it it, crossfeeding the upper stages would be a better idea than what I had.

I wish I had time to do some number - crunching for that, but it's way later than I should be awake on a weekday, and I don't think my brain's up to the task.

[kch]

Oh, my, that thing's quite a monster. 

It is that ... and then there's its big brother:

http://www.astronautix.com/lvs/ur900.htm

[MattJL]

Well, uh, *whistles.*  I have no words for that. 

I've gotten the chance to do the math behind the CCU vehicle (which I really should name to make it easier to talk about.  I was thinking "Apex"), and based off some really basic numbers (burn times, namely, since the engines would have the same specifications as the H-1 and J-2), this thing could indeed deliver a payload to the Moon.  Whether or not that payload is useable is something I have to work out later, as I'm in a bit of a rush right now.

Mornings are not my friends. 

EDIT: I've finally got enough time to explain my logic, mainly that the Apex vehicle (as I've decided to call this thing) would have enough propellant to get a payload to the Moon based off the Saturn V's burn time values.

So the first stage of the vehicle (5 CCUs) has the same burn time (150 s) as the S-IC.  The five CCUs provide slightly more thrust than the S-IC (36 kN, compared to the 33.85 kN of the S-IC), so the first stage is more than capable of matching the S-IC's performance.

The second flight phase of the Apex LV would see all 5 J-2 engines on the upper CCU stages burning all at once for 367 seconds, with the outer 4 stages feeding the center engine.  The S-IVB type stages have just enough hydrolox to feed the center engine (assuming 1/4 of the propellant from the outer stages is diverted into the center stage, which leaves each outer stage with 383 s of propellant, and the inner stage with the required 367 seconds of propellant).  This leaves about 16 seconds of residual propellant in the outboard S-IVBs which probably will not be used, but fueled anyway.  Propellant could be spread out between all 5 engines, extending their burn time for heavier payloads.

At separation of the outer upper CCU stages, the center S-IVB completes the burn to orbit (depleting about 86 s worth of propellant) and then TLI (which burns to depletion).

Since these are the Apollo spacecraft numbers (same amount of thrust and similar mdot in all stages), but with a slightly better performance lower stage, I don't think it's unreasonable to assume that Apex could loft 45 t to the Moon.

[Archibald]

UR-700 and UR-900 were to be filled with enough hypergols to sterilize a large chunk of Kazakhstan if they ever failed at takeoff... 

[RanulfC]

UR-700 and UR-900 were to be filled with enough hypergols to sterilize a large chunk of Kazakhstan if they ever failed at takeoff... 

Lesson to learn here: NEVER "tempt-fate" by declaring "That could never happen" but instead make realistic plans for when it WILL happen

You'll sleep better

"By January 1969, Chelomei was proposing the UR-900 for the Mars expedition. Chertok asked Chelomei what would happen if, God forbid, such a booster exploded on the launch pad. Wouldn't the entire launch complex be rendered a dead zone for 18 to 20 years? Chelomei's reply was that it wouldn't explode, since Glushko's engines were reliable and didn't fail. Aside from that, these propellants had been used in hundreds of military rockets, deployed in silos, aboard ships and submarines, with no problem. Fear of these propellants was irrational. Related propellants were used by the Americans on the Apollo manned spacecraft.

Less than three months later, on 2 April 1969, the unimaginable happened. A Proton rocket, one tenth the size of the planned UR-900, was launched in an attempt to send an unmanned probe to Mars. The leadership of the Soviet Rocket Forces and most of the Chief Designers were present for the event. The Proton rocket lifted off, but one engine failed. The vehicle flew at an altitude of 50 m horizontally, finally exploding only a few dozen meters from the launch pad, spraying the whole complex with poisonous propellants that were quickly spread by the wind. Everyone took off in their autos to escape, but which direction to go? Finally it was decided that the launch point was the safest, but this proved to be even more dangerous - the second stage was still intact and liable to explode. The contamination was so bad that there was no way to clean up - the only possibility was just had to wait for rain to wash it away. This didn't happen until the Mars 1969 launch window was closed, so the first such probe was not put into space until 1971"

From:
http://www.astronautix.com/lvs/ur700m.htm

Randy

[simonbp]

And yet, the Russians still launch Protons (aka UR-500), with precisely the same propellants. And the US kept launching Titans well into the 21st century (despite a number of detonations), and the Chinese are great fans of hypergolic Long Marches too.

Chelomei's plan for UR-700 from the start was to ground test each and every module at the factory outside Moscow before sending them by rail to the launch site. It wouldn't have been perfect, but it would probably have more reliable than N-1...

[MattJL]

UR-700 and UR-900 were to be filled with enough hypergols to sterilize a large chunk of Kazakhstan if they ever failed at takeoff... 

I'd be more fearful of the UR-900's nuclear upper stage.