new launch vehicle

[hurricane4911]

What's your problem?<br /><br />I try to be friendly and contribute, and you got some kind of bug up your a$$.<br />

 

[propforce]

<blockquote><font class="small">In reply to:</font><hr /><p>"how do you arrive the 12.5% of total (initial) propellant mass as the required landing mass, when you don't know what the landing weight of the vehicle is?" <br /><br />Simple rocket equation calculation finding out what the required massratio is to achieve 30s * g + 400km/h deltaV when you have 350s specific impulse. The reality is of course much more complex as you pointed out in the rest of your post! But it was something to start with. <p><hr /></p></p></blockquote><br /><br />Thank you for the explanation. I mis-read as well. The 12.5% is the landing propellant weight as a % of final landing weight, not a % of initial propellant (which would be a very big number !!).<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[tap_sa]

Ah, forgot to say in the original post that the 12.5% is from the landing mass. My bad, 4:30am in here <img src="/images/icons/smile.gif" />

 

[gawin]

A quick couple points on parachutes.<br /><br />1. Due to the great speeds atained by the shuttle durring landing and the rather short runway at KSC the shuttles all have a parachute. all though smaller and less wieght they still have one. so little savings thier.<br /><br />2. SPF. (Single Point of Failure)reling on any one single system to get you down is not safe. having your parachutes as your one and only meens of slowing your decent to a safe landing is proven but is also provin to have a fairly high fail rate as oposed to wings. case in point the space craft that just slamed into the ground at 200mph due to a chute failing.<br /><br />we need to look at new answers to thies questions and find a new means of safly landing a craft.<br /><br />gawin

 

[john_316]

Ok here is my 2 cents worth.<br /><br /><br />Build a DC-Y demonstrator and fly it in several suborbital flights and then do an LEO flight or two all unmanned with remote control.<br /><br />Build the CEV in a capsule configuration and test it unmanned on an SRB.<br /><br />Build the CEV in a Lifting body configuration and test it unmanned on the SRB or EELV.<br /><br />Finish the X-33 demonstrator and flight test it for suborbital flight now that fuel tanks aren't a problem.<br /><br />Perhaps they can figure out a way to insulate the insulation on the sides that face the orbiter on launch perhaps with a kevlar or nylon netting on certain areas near the underbelly of the orbiter. I think this netting as mentioned before can actually be applied without too much weight gain to the ET and it may keep the foam on that side of the ET more intact and allow the shedding to occur later on.<br /><br />I think the idea that the shuttle sits in the Florida weather for weeks on end has an effect on the ET insulation. <br /><br /><br /><img src="/images/icons/smile.gif" /><br /><br />

 

[tap_sa]

<font color="yellow">"The ventustar was to be unmanned . On that one point alone how could it be a Shuttle replacement? "</font><br /><br />Stowaway astronauts hiding in wheel wells? <img src="/images/icons/smile.gif" />

 

[nacnud]

Well you can see the confusion.<br /><br />The Shuttle is being retired; the CEV will become the new manned launch vehicle. The Shuttle is being replaced by the CEV in the respect that it will be come the new US manned launch vehicle, even if the capabilities of the two systems don't overlap beyond them both being manned.<br /><br />When you have only a sentence to describe the shuttle and the CEV, replacement seems a valid word to use.<br />

 

[no_way]

To sum it up. <br /><br />Each landing method, including horizontal landing with wings, parachute/parafoil landing and vertical landing on rockets has its own pro's and cons, none of them is "free" performance-wise, each of them costs payload.<br /><br />But its not the performance that matters most. Its reliability ( and usually, simpler systems are more reliable ), maintainability, turn-around time and operability that matter most for low-cost vehicles at least.<br />Vertical landing is (arguably) the simplest method of those. The requirements that it adds to any launch vehicle are deep-throttleable engines , more precise 3-D positioning methods and some software. Even deep-throttling can be avoided if you are using a cluster of engines for other purposes anyway.<br /><br />Compare it to horizontal landing with wings, which requires you to have a certain body shape which will make your launch aerodynamics and reentry thermal protection immediately more complex, not to speak of landing gear requirements.<br /><br />Compare it to parachute systems, which have worst turn-around time, often require water landing which will in turn bring up issues with buoyancy and salt water effects, and also have worst-case failure modes that are very dangerous to general public ( like deployment at high-altitude) which kills any prospects of reasonable insurance for commercial vehicle at least.<br /><br />And i want to reiterate, VTVL doesnt imply SSTO. Its perfectly possible to build a reuseable, two-stage VTVL orbital vehicle.<br /><br />So a blanket statement of "DC-X wasnt leading us anywhere because of deep gravity well and its not making use of thick atmosphere for landing" is IMO seriously short-sighted.

 

[tomnackid]

Last week there were at least 3 major truck accidents on I-84 one fatal. A tour bus went up in flames also in I-84 (no injuries), and the week before a tanker full of gasoline flipped just outside of Danbury, burst into flames and killed the driver and did major damage to the road and overpass. Roads have been around since the Sumerians, internal combustion engines and traffic lights for about a hundred years, The interstate highway system for about 50 years. <br /><br />The shuttle goes from 0 to 18,000 mph in 9 minutes. It carries 25 tons into orbit and can bring 14 tons back. NOTHING else existing or on the table for the immediate future can do that. Maybe we just need to put things into perspective.

 

[craig42]

What if the primaries are refuled in orbit? No need to carry fuel or retro rockets for landing up with you. Of course an earlier flight or space mining is needed to get the fuel there.

 

[propforce]

"...I think that stuffing the foam inside the ET would be the best first idea to try. While trying that idea, other ideas should be prototyped, that is if the STS flies again. ...."<br /><br />I think they should use bolsa wood (a.k.a. cork) for insulation. <img src="/images/icons/laugh.gif" /><br /> <div class="Discussion_UserSignature"> </div>

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>But its not the performance that matters most. Its reliability<p><hr /></p></p></blockquote><br />BING BING BING BING BING BING BING<br /><br />WE HAVE A WINNER!!!!!<br /><br />It is my mantra in the software industry: "Never code for performance, unless performance is the primary design requirement. Performance is NEVER the primary design requirement." Back when computers were slow and had little memory, yeah, you needed to worry about performance. Today, the hardware is more than capable of running MAINTAINABLE code with no concerns for absolute efficiency. So, write your code to be maintainable, not performant. Of course, use good engineering principles to avoid unnecessarily inefficient code, but maintenance is your first priority ALWAYS.<br /><br />Engineers LOVE performance. They love mins and maxes. But, at some point, maximizing performance becomes a waste of time. When we were just starting in space, we had steel, aluminum and titanium, and rocket engine technology was in its infancy. We had to min/max to do what we did. Today, we are at the point where materials science and rocket engine tech allows us to reduce weight much easier. So, it behooves us to use those weight savings to improve reliability, not to eek out yet more performance. <br /><br />BUT, just like in software, don't make stupid engineering decisions. Weight is still a concern. Don't put unnecessary weight on the vehicle. Spheres, cylinders and cones are still the most efficient and strongest shapes for tanks. So, DON'T BE BUILDING NO LIFTING BODIES!!!! Rockets want to be cylinders. The DC-X system neatly and efficiently fits in to this paradigm. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[radarredux]

> <i><font color="yellow">"Never code for performance, unless performance is the primary design requirement. Performance is NEVER the primary design requirement."</font>/i><br /><br />Great line! It reminds me of some comments in a recent The Space Review interview with TGV:<br /><blockquote><font class="small">In reply to:</font><hr /><p>Ask any aerospace engineer how you make something better, every time their version of better will be flight performance. It’s a built-in bias.<br />...<br />Do you know how to separate the people who are going to be successful from the people who aren’t? Ask them to describe their business. If they start out with talking about propellant, taking about their apogee, talking about their carrying capacity or passengers or payload or flight rating or anything else, “Bye.” Pat’s phrase is, “Amateurs talk propulsion, professionals talk insurance.”<p><hr /></p></p></blockquote><br />http://www.thespacereview.com/article/417/1</i>

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>Great line!<p><hr /></p></p></blockquote><br />You would not believe how many times I tell that to an Electrical Engineer cum Software Engineer and get a look of shocked incredulity in return. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[skywalker01]

Unfortunately, in the case of all chemical rocket powered launch vehicles, their maximum payload fraction is between 1 and 2 percent. It doesn't matter if they are VTOHL or VTOVL, that is the best they can do. That means that the lowest cost to orbit that these vehicles can get is around $1000/lb. That is still too much money for really large-scale high-volume space operations.<br />Really large scale space operations will require LVs with payload fractions of 10 percent or greater and costs to LEO of $200/lb or less.<br /><br />So how about some 'out of the box' thinking on ways to achieve this?

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>So how about some 'out of the box' thinking on ways to achieve this? <p><hr /></p></p></blockquote><br />Space Elevator <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>maximum payload fraction is between 1 and 2 percent. ..cost to orbit that these vehicles can get is around $1000/lb<p><hr /></p></p></blockquote><br />You just pulled this $1000/lb number out of thin air ? This is utter non-sequitur. <br />Assume lox-kerosene propulsion, assume payload fraction of one and try calculate how much the fuel exactly costs which you burn to get to orbit.<br />LOX costs about five cents a pound, rocket-grade kerosene about 25c. The mixture is 3/4 LOX by weight.<br /><br />See what numbers you get.<br />

 

[larper]

Am I right in getting about $12 per pound? <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[gunsandrockets]

"The CEV is 30 mt not the payload. The payload with the crew is in the range of 1,000 pounds at the most."<br /><br />The Lockheed-Martin CEV GLOW is less than 20 tonnes and carries a payload of 5,000 pounds of cargo in addition to a crew of up to six. That may change under whatever new requirements Griffin makes to the CEV program, but the numbers I quote are current as of May.

 

[skywalker01]

I should have said;<br /><br />So how about some 'out of the box thinking' on ways to achieve this based on existing technology.<br /><br />I assume by 'space elevator' you are refering to the concept that goes from the Earth surface to geostationary orbit and beyond that requires CNT fibers of a certain strength to weight ratio. It is also my understanding that the current materials work on CNT fibers doesn't even come close to matching the strength to weight ratio of commercially available graphite fibers.<br />So as much as I look forward to someday being able to get on an elevator and ride it to space, what I am more interested in right now is what can be done right now to break out of the 1 to 2 percent payload fraction limitation of chemical powered launch vehicles.<br /><br />Ideas that I am currently aware of:<br />1) ground accelerator launched rockets,<br />2) ground accelerator launched ramjet/rockets,<br />3) ground accelerator launched ramjet/scramjet/rockets,<br />4) RBCC,<br />5) ground accelerator launched RBCC,<br />6) ducted rocket,<br />7) ground accelerator launched ducted rocket,<br />8) TRCC,<br />9) 1 thru 8 in combination with an Earth Orbiting Elevator,<br />10) 1 thru 8 as reusable first stage LVs with expendable upper stages,<br />11) laser launch,<br />12) big dumb booster,<br /><br /><br />Do you know of any others?<br />

 

[davf]

Balsa was actually considered for the S-IV. Among other issues, they found that the entire world's balsa supply could not provide enough for Apollo.

 

[skywalker01]

I based the $1000/lb on what the Soviets offered to sell launch services for back in the late 80's when they were launching 60 plus times a years.

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>Am I right in getting about $12 per pound?<p><hr /></p></p></blockquote><br />Absolutely. About $25 if you insists on using LH2 instead of kerosene.<br /><br /><blockquote><font class="small">In reply to:</font><hr /><p>I based the $1000/lb on what the Soviets offered to sell launch services for back in the late 80's when they were launching 60 plus times a years<p><hr /></p></p></blockquote><br />With hardware that is basically a direct descendant of expendable ammunition. Sure you can up the costs through the roof if you pay for a new vehicle each launch.<br />But thats not the way practical transportation systems are built.

 

[larper]

Basically, there are two, and only two, ways of getting into orbit:<br /><br />1) Fast. This includes rockets and all of their derivatives, airlaunched systems, ground launched system, air breathers, anything that requires that you go very fast while still in the atmosphere and achieve orbital velocity.<br /><br />2) Slow. You creep out of the atmosphere and, once in space, boost up to orbital velocity. This would include Space elevators and their derivatives, as well as some sort of "constant thrust" system that allows you to achieve altitude slowly until you are safely away from the atmosphere and can "turn left and boost". Ground based laser systems might fit in this category.<br /><br />I think that any system in the first (fast) category is simply trying to get around the inherent limitations of that method. Thus, ground accelerators, fancy rockets, etc, only mitigate the problem slightly, they don't solve it. All they end up doing is adding complexity.<br /><br />So, I am in favor of using proven, simple systems that are highly reliable. Something that we can use for the long term while we research and strive for the slow systems of the future that will REALLY change things.<br /><br />So, I want a small, highly reliable, simple system for manned launches (DC-X type, perhaps). No payload. Just people.<br /><br />Then, I want a HLLV (shuttle derived is fine by me) to launch payloads. Big payloads. HUGE payloads. <br /><br />We have to get away from the "single system" mentality. If people drove to work like NASA goes to space, we would all drive Winnebagos. I want our space launch system to be a mix of Civics and Semis. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>

 

[larper]

<blockquote><font class="small">In reply to:</font><hr /><p>With hardware that is basically a direct descendant of expendable ammunition. Sure you can up the costs through the roof if you pay for a new vehicle each launch. <br />But thats not the way practical transportation systems are built. <p><hr /></p></p></blockquote><br />You have to get over the assumption that reusability implies cost savings. If it is cheaper to throw the whole thing away and build a new one, then that is the way to go. That basic assumption lead directly to STS. <div class="Discussion_UserSignature"> <p><strong><font color="#ff0000">Vote </font><font color="#3366ff">Libertarian</font></strong></p> </div>