SpaceX to build a BFR

[gunsandrockets]

Most of this thread has dwelled on the virtue (or lack) of SpaceX and alt.space rocketry. I would like to drag it back into a discussion of the BFR and the Merlin 2 rocket engine.<br /><br /><br /><br />Here is something interesting from the http://www.thespacereview.com/article/497/1 article about the Merlin 2...<br /><br />"Musk said that the Merlin 2 will be, in general, a scaled-up version of the Merlin 1. One change that SpaceX does plan, he noted, was to replace the ablative engine chamber with a regeneratively-cooled one."<br /><br />So the SpaceX plan for the BFR revolves around a conventional LOX/RP-1 pump-fed multi-engine rocket. That is really a recreation of the Saturn V concept, not a BDB. A Big Dumb Booster is a low performance rocket that compensates by increased size, such as the Truax concept of a pressure-fed booster.<br /><br />Even with the smaller and more effecient size of a Saturn style rocket, BFR size and weight would be a serious issue for transport to launch site and the launch site infrastructure. The costs of the Merlin 2 development and BFR production could be a minor part of the total costs of operation because of the transportation and infrastructure costs. Absent close co-ordination with NASA, I can't see how those issues are overcome (plus NASA's VSE is the only realistic market for the BFR).<br /><br />Going the very conventional design route with the Merlin 1, Merlin 1a and Merlin 1c, makes a lot of sense for the smaller Falcon 1 and Falcon IX rockets, but I think SpaceX has made the wrong choice with the Merlin 2. I predict the first successful private company venture which flys a Saturn class heavy lift booster will employ the cost reduction principles of the Truax Big Dumb Booster: a large pressure-fed rocket which is sea-launched.<br /><br />

 

[barrykirk]

What about a sea-launch Saturn V class rocket?<br /><br />Does that make any sense?

 

[barrykirk]

What about a sea-launch Saturn V class rocket?<br /><br />Does that make any sense?

 

[mikejz]

The Merlin 2 is clearly just on the drawing board. My bet however is that in the longer term, after some flight experence, to cut the Falcon IV down from 9 Merlin 1s to a single Merlin 2.

 

[mikejz]

The Merlin 2 is clearly just on the drawing board. My bet however is that in the longer term, after some flight experence, to cut the Falcon IV down from 9 Merlin 1s to a single Merlin 2.

 

[mlorrey]

"I absolutely agree that NASA cannot depend on private space to do anything. They must develop government-owned access to space. Understanding this fact of life is one of the reasons I fully support ESAS. "<br /><br />Now, replace "space" with "air travel". Where are your national airlines? Oh, yea, over in those socialist countries.<br /><br />The only reason private space is considered unreliable is that the socialists in government have absolutely no faith in the market. It is unamerican.<br />

 

[mlorrey]

"I absolutely agree that NASA cannot depend on private space to do anything. They must develop government-owned access to space. Understanding this fact of life is one of the reasons I fully support ESAS. "<br /><br />Now, replace "space" with "air travel". Where are your national airlines? Oh, yea, over in those socialist countries.<br /><br />The only reason private space is considered unreliable is that the socialists in government have absolutely no faith in the market. It is unamerican.<br />

 

[barrykirk]

As far as I know, the Falcon IX, at least the version with a single core is built en-masse at a factory and shipped to the launch site as one piece.<br /><br />With the Saturn V, the components were shipped to NASA and assembled in the VAB. Transport of the assembled vehicle to the launch pad involved a huge amount of expense and technology.<br /><br />They couldn't launch directly from the VAB, because the VAB was very expensive and a KABOOM at liftoff would have totaled the building.<br /><br />Would it be possible to build a cheaper VAB today where instead of moving the rocket, move the assembly equipement?<br /><br />Or as I suggested up above, combine the BDR concept with the Saturn V concept. Sea Launch a Saturn V or equivalent?<br /><br />Question, how badly do rockets perform when fired underwater? How many seconds does it take for a rocket to clear the water's surface? I guess that depends on how deep underwater the rocket engine itself is.<br /><br />Does sea launch reduce the total payload and if so, by how much?<br /><br />Just questions?

 

[barrykirk]

As far as I know, the Falcon IX, at least the version with a single core is built en-masse at a factory and shipped to the launch site as one piece.<br /><br />With the Saturn V, the components were shipped to NASA and assembled in the VAB. Transport of the assembled vehicle to the launch pad involved a huge amount of expense and technology.<br /><br />They couldn't launch directly from the VAB, because the VAB was very expensive and a KABOOM at liftoff would have totaled the building.<br /><br />Would it be possible to build a cheaper VAB today where instead of moving the rocket, move the assembly equipement?<br /><br />Or as I suggested up above, combine the BDR concept with the Saturn V concept. Sea Launch a Saturn V or equivalent?<br /><br />Question, how badly do rockets perform when fired underwater? How many seconds does it take for a rocket to clear the water's surface? I guess that depends on how deep underwater the rocket engine itself is.<br /><br />Does sea launch reduce the total payload and if so, by how much?<br /><br />Just questions?

 

[barrykirk]

After posting this, I had another thought.<br /><br />Could a rocket be made in sections, and assembled on the pad by a mobile crane?<br /><br />Once assembled, the crane drives away from the rocket which is then fueled.<br /><br />With a Saturn V,<br /><br />The second stage is roughly 39 tons empty.<br /><br />I found a mobile crane <br /><br />http://www.liebherr.com/at/en/57688.asp<br /><br />with adequate lifting capacity, 500 tonnes, and 145meters hoist height.<br /><br />A fully assembled Saturn V is about 120 meters.<br /><br />That reduces the size of the components to something that could be shipped and then assembled on the pad.<br /><br />No VAB is necessary.<br /><br />Now, I understand that NASA did a lot of welding in the VAB when assembling the rockets.<br /><br />If the components are too big to ship from the factory to the launch pad. What about using clustering or multiple cores. Each core would have a smaller diameter than one large tank.<br /><br />I understand that this cuts way down on efficiency of the rocket because their is more tank mass per pound of fuel. But it improves logistical efficiency in that the pieces can be built in a factory and then shipped to the launch site.

 

[barrykirk]

After posting this, I had another thought.<br /><br />Could a rocket be made in sections, and assembled on the pad by a mobile crane?<br /><br />Once assembled, the crane drives away from the rocket which is then fueled.<br /><br />With a Saturn V,<br /><br />The second stage is roughly 39 tons empty.<br /><br />I found a mobile crane <br /><br />http://www.liebherr.com/at/en/57688.asp<br /><br />with adequate lifting capacity, 500 tonnes, and 145meters hoist height.<br /><br />A fully assembled Saturn V is about 120 meters.<br /><br />That reduces the size of the components to something that could be shipped and then assembled on the pad.<br /><br />No VAB is necessary.<br /><br />Now, I understand that NASA did a lot of welding in the VAB when assembling the rockets.<br /><br />If the components are too big to ship from the factory to the launch pad. What about using clustering or multiple cores. Each core would have a smaller diameter than one large tank.<br /><br />I understand that this cuts way down on efficiency of the rocket because their is more tank mass per pound of fuel. But it improves logistical efficiency in that the pieces can be built in a factory and then shipped to the launch site.

 

[mlorrey]

I have seen some launch pads that had roll away or fall-away VAB-like enclosures. The VAB itself, though, is so huge that making it mobile would certainly be difficult.<br /><br />I would have to say offhand that the fact that the VAB is so huge that it is NOT mobile may be a reason for the huge standing army problem. Its lack of mobility encourages employing a standing army, where insisting on smaller, more mobile facilities would give the hordes of union workers no where to layabout or otherwise hide from supervisors. Smaller facilities would be less complex facilities, requiring fewer facilities personnel, as well.<br /><br />Having the worlds biggest building for the sake of having the worlds biggest building is not a rationale for doing it at a launch facility.

 

[mlorrey]

I have seen some launch pads that had roll away or fall-away VAB-like enclosures. The VAB itself, though, is so huge that making it mobile would certainly be difficult.<br /><br />I would have to say offhand that the fact that the VAB is so huge that it is NOT mobile may be a reason for the huge standing army problem. Its lack of mobility encourages employing a standing army, where insisting on smaller, more mobile facilities would give the hordes of union workers no where to layabout or otherwise hide from supervisors. Smaller facilities would be less complex facilities, requiring fewer facilities personnel, as well.<br /><br />Having the worlds biggest building for the sake of having the worlds biggest building is not a rationale for doing it at a launch facility.

 

[tap_sa]

<font color="yellow">"Would it be possible to build a cheaper VAB today where instead of moving the rocket, move the assembly equipement? "</font><br /><br />Two words; horisontal assembly<br /><br />Stacking up and transporting Saturn V sized vehicles vertically is magnificent technical feat per se, but not very practical. If NASA can't exploit reliable Russian hardware (RD-180) could it at least exploit their vehicle handling procedures? Integrate everything while vehicle is horisontally. Ship that way to launch pad where support structure turns into LUT after tilting the (empty) vehicle vertical.<br /><br />The minimum hardcore version of horisontal assembly VAB would be only long enough to house welding machine and one barrel section <img src="/images/icons/smile.gif" /> Finished vehicle would extrude from the building into transport rail. Some shipyards build ships this way.

 

[tap_sa]

<font color="yellow">"Would it be possible to build a cheaper VAB today where instead of moving the rocket, move the assembly equipement? "</font><br /><br />Two words; horisontal assembly<br /><br />Stacking up and transporting Saturn V sized vehicles vertically is magnificent technical feat per se, but not very practical. If NASA can't exploit reliable Russian hardware (RD-180) could it at least exploit their vehicle handling procedures? Integrate everything while vehicle is horisontally. Ship that way to launch pad where support structure turns into LUT after tilting the (empty) vehicle vertical.<br /><br />The minimum hardcore version of horisontal assembly VAB would be only long enough to house welding machine and one barrel section <img src="/images/icons/smile.gif" /> Finished vehicle would extrude from the building into transport rail. Some shipyards build ships this way.

 

[trailrider]

"Question, how badly do rockets perform when fired underwater?"<br /><br />The backpressure of the water reduces the exhaust velocity considerably. How much depends, as in the atmosphere, on the initial pressure, which in turn is determined by how deep the nozzle is under the water. (I seem to recall that the pressure of water doubles for every six feet in depth, but you scuba divers will have to verify that for me!)<br /><br />"How many seconds does it take for a rocket to clear the water's surface? I guess that depends on how deep underwater the rocket engine itself is."<br /><br />How quickly the rocket rises depends on the thrust-to-weight ratio, just as on land. <br /><br />"Does sea launch reduce the total payload and if so, by how much?" <br /><br />Don't have the answer for you... Depends on a lot of factors, just as launch from land does.<br /><br />"I predict the first successful private company venture which flys a Saturn class heavy lift booster will employ the cost reduction principles of the Truax Big Dumb Booster: a large pressure-fed rocket which is sea-launched."<br /><br />"The minimum hardcore version of horisontal assembly VAB would be only long enough to house welding machine and one barrel section Finished vehicle would extrude from the building into transport rail. Some shipyards build ships this way."<br /><br />R.C.'s original concept included building the pressure-fed BDB in shipyards, floating them out to sea, fueling them in such a way that they would erect themselves horizontally, and then firing them. Part of this concept was called Sea Dragon.<br /><br />I wish I could recall more details of the thing...there IS or was a website about Truax and Sea Dragon. Haven't checked there in awhile.<br /><br />One of the reasons for the pressure-fed type booster was that the state-of-the-art for large turbopumps hadn't gone much beyond feeding 150,000 lbf liquid engines. (This was 1960-1962 timeframe.) Pressure feeding also was to save the weight of the turbo

 

[trailrider]

"Question, how badly do rockets perform when fired underwater?"<br /><br />The backpressure of the water reduces the exhaust velocity considerably. How much depends, as in the atmosphere, on the initial pressure, which in turn is determined by how deep the nozzle is under the water. (I seem to recall that the pressure of water doubles for every six feet in depth, but you scuba divers will have to verify that for me!)<br /><br />"How many seconds does it take for a rocket to clear the water's surface? I guess that depends on how deep underwater the rocket engine itself is."<br /><br />How quickly the rocket rises depends on the thrust-to-weight ratio, just as on land. <br /><br />"Does sea launch reduce the total payload and if so, by how much?" <br /><br />Don't have the answer for you... Depends on a lot of factors, just as launch from land does.<br /><br />"I predict the first successful private company venture which flys a Saturn class heavy lift booster will employ the cost reduction principles of the Truax Big Dumb Booster: a large pressure-fed rocket which is sea-launched."<br /><br />"The minimum hardcore version of horisontal assembly VAB would be only long enough to house welding machine and one barrel section Finished vehicle would extrude from the building into transport rail. Some shipyards build ships this way."<br /><br />R.C.'s original concept included building the pressure-fed BDB in shipyards, floating them out to sea, fueling them in such a way that they would erect themselves horizontally, and then firing them. Part of this concept was called Sea Dragon.<br /><br />I wish I could recall more details of the thing...there IS or was a website about Truax and Sea Dragon. Haven't checked there in awhile.<br /><br />One of the reasons for the pressure-fed type booster was that the state-of-the-art for large turbopumps hadn't gone much beyond feeding 150,000 lbf liquid engines. (This was 1960-1962 timeframe.) Pressure feeding also was to save the weight of the turbo

 

[trailrider]

Well, I went to the website that talks about Truax and the various rockets he proposed.<br /><br />http://www.astronautix.com/lvs/searagon.htm<br /><br />Look for Truax and Sea Drago, Sea Horse, etc.<br /><br />Still doesn't say if he's alive or not... <img src="/images/icons/frown.gif" /><br /><br />Ad anywhere beyond LEO!

 

[trailrider]

Well, I went to the website that talks about Truax and the various rockets he proposed.<br /><br />http://www.astronautix.com/lvs/searagon.htm<br /><br />Look for Truax and Sea Drago, Sea Horse, etc.<br /><br />Still doesn't say if he's alive or not... <img src="/images/icons/frown.gif" /><br /><br />Ad anywhere beyond LEO!

 

[josh_simonson]

You get 1ATM for every 33 feet, not 6. I'd implode diving for abalone otherwise. <img src="/images/icons/wink.gif" /><br /><br />It's interesting to note that the bottom of the SRB is exactly 120ft down during the recovery operation, that's the maximum limit for standard scuba diving. If it were much deeper they'd have to use considerably more exotic gear.

 

[josh_simonson]

You get 1ATM for every 33 feet, not 6. I'd implode diving for abalone otherwise. <img src="/images/icons/wink.gif" /><br /><br />It's interesting to note that the bottom of the SRB is exactly 120ft down during the recovery operation, that's the maximum limit for standard scuba diving. If it were much deeper they'd have to use considerably more exotic gear.

 

[mlorrey]

Thats right, Josh, one of the reasons there is criticism of the 5 segment booster concept, which extends the depth requirements to 150 feet. It would be safer all around if they had Aerojet revive its 260 inch monolithic booster design.

 

[mlorrey]

Thats right, Josh, one of the reasons there is criticism of the 5 segment booster concept, which extends the depth requirements to 150 feet. It would be safer all around if they had Aerojet revive its 260 inch monolithic booster design.

 

[mlorrey]

"The backpressure of the water reduces the exhaust velocity considerably. How much depends, as in the atmosphere, on the initial pressure, which in turn is determined by how deep the nozzle is under the water. (I seem to recall that the pressure of water doubles for every six feet in depth, but you scuba divers will have to verify that for me!) "<br /><br /><br />Thrust should improve given that the pressure of the water creates more pressure on the exhaust gasses. While exhaust velocity drips, chamber pressure should increase considerably. Like being fired from a gun.

 

[mlorrey]

"The backpressure of the water reduces the exhaust velocity considerably. How much depends, as in the atmosphere, on the initial pressure, which in turn is determined by how deep the nozzle is under the water. (I seem to recall that the pressure of water doubles for every six feet in depth, but you scuba divers will have to verify that for me!) "<br /><br /><br />Thrust should improve given that the pressure of the water creates more pressure on the exhaust gasses. While exhaust velocity drips, chamber pressure should increase considerably. Like being fired from a gun.