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#26 2004-04-03 19:50:27

SBird
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Registered: 2004-03-10
Posts: 490

Re: Earth to LEO - revisited - another direction

That's true, it's down to about $10,000/kg these days.  The lowest cost is for the Shtil converted Russian ICBM launcher that can get $465/kg to LEO.  Of course, that tops out at something like 250 kg...

I've been using [http://www.futron.com/pdf/FutronLaunchCostWP.pdf]this link for most of my figures.

The Pegasus launcher is the most expensive per pound for some reason, topping out at ~$15,000/lb.  I have a feeling that Pegasus won't be around too much longer at those prices.

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#27 2004-04-03 19:52:49

Bill White
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Registered: 2001-09-09
Posts: 2,114

Re: Earth to LEO - revisited - another direction

That's true, it's down to about $10,000/kg these days.  The lowest cost is for the Shtil converted Russian ICBM launcher that can get $465/kg to LEO.  Of course, that tops out at something like 250 kg...

I've been using [http://www.futron.com/pdf/FutronLaunchCostWP.pdf]this link for most of my figures.

The Pegasus launcher is the most expensive per pound for some reason, topping out at ~$15,000/lb.  I have a feeling that Pegasus won't be around too much longer at those prices.

Look at the bottom of page 1 of this report. This suggests a 20% to 30% drop between the prices published in the report and today.

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#28 2004-04-03 19:56:25

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Earth to LEO - revisited - another direction

Pegasus is a special order rocket, since its air launched it can reach any orbital inclination you want easily.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#29 2004-04-04 04:23:26

SBird
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Posts: 490

Re: Earth to LEO - revisited - another direction

Bill, I'm not counting on the recent drop in prices since it is an artificial result of a soft launch market.  Obviously, if demand picks back up for Mars mission support, the price will go back up.  These companies can't sustain operations at break-even or loss indefinately.

GCNR - Sea Launch can also go from any arbitrary orbital inclination as well and is the cheapest (pseudo) Western launch system around.  What gets me is that Pegasus gains the advantage of a high altitutde launch which should reduce launch costs.  I remember that Pegasus was originally touted as being this super-cheap launcher to get small payloads to orbit.  Now, it's at least 3 times the cost per pound of clunkers like the Shuttle.  What happened?

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#30 2004-04-05 04:41:02

Gennaro
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From: Eta Cassiopeiae (no, Sweden re
Registered: 2003-03-25
Posts: 591

Re: Earth to LEO - revisited - another direction

Personally, I say that we give the ISS to the ESA, Russians and Chinese.  And walk all the way back to the bank laughing.

Just a sidenote, disregarding the fact that you are obviously not too sincere about it, I've seen this sentiment expressed rather frequently by Americans disenchanted with the ISS. Yet why do you believe Europeans, Russians and Chinese are less able to see the uselessness of the International Space Station or the money drain it represents if you do? Why must we be obliged to inherit and take responsibility for it if NASA walks away?
After all, wasn't this all your idea to start with, something called "Space Station Freedom" or similar, or have I missed something?

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#31 2004-04-05 09:53:04

SBird
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Posts: 490

Re: Earth to LEO - revisited - another direction

It's less of a matter of not believeing that other countries will see the deficiencies of ISS but rather a case of *hoping* they won't see it.  Sort of like someone trying to sell an old junker of a car and hoping that the buyer doesn't notice that the bumpers are held on with duct tape.

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#32 2004-04-05 10:11:10

Gennaro
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From: Eta Cassiopeiae (no, Sweden re
Registered: 2003-03-25
Posts: 591

Re: Earth to LEO - revisited - another direction

It's less of a matter of not believeing that other countries will see the deficiencies of ISS but rather a case of *hoping* they won't see it.  Sort of like someone trying to sell an old junker of a car and hoping that the buyer doesn't notice that the bumpers are held on with duct tape.

He, he, well, I guess you're always welcome to try. big_smile

I've got a better idea though. Let's all dump the ISS and I'll force the EU Commission to put half the cash on the table for a joint NASA/ESA Mars venture.
big_smile

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#33 2004-04-06 19:14:56

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Earth to LEO - revisited - another direction

Now that we've got another thread about the ISS and its future, a nudge back on topic... Seeing pictures of hypersonic airplanes here and there following the sucessful X-43A flight got me poking around in spare time, but it is looking pretty clear that a Scramjet SSTO is a ways off still without massive development dollars.

Anyways, we will need a fully reuseable vehicle eventually to do more than get our feet Red or develop anywhere, so i'd like to reopen the thread and think soley about RLV vehicles, especially concerning concepts and neat technologies that might make them practical as a commertial medium launcher to do what Shuttle was promised/feigned to do... inexpenive, reliable, and regular flights to LEO.

The best one that i've seen for medium weight cargo (25MT) and people without getting too heavy is a two-stage horizontal takeoff vehicle. The lower stage, a big airplane, could be powerd up to low/mid mach numbers and high altitudes with conventional turbine engines, Mach 6 with LOX augmented turbines, then seperate and the upper stage keeps going to orbit on rocket power.

Expensive to develop and build, but that would do it. A neat trick that piqued my interest, mentions of a system called "ACES" for making LOX in mid air to minimize takeoff weight and hence total vehicle mass. Anybody know much about that?

Finally wondering if Slush Hydrogen would change the equation to make this kind of vehicle easier to do. Anybody know of any recent-ish work on it as a fuel?

Also wondering if the DC-X concept could be refined to increase payload mass, which as it stands at the moment is around 10MT for a production-scale vehicle using the most efficent rocket there is, a LOX/LH2 Radial Aerospike, and carbon composit materials.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#34 2004-04-07 11:30:11

SBird
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Re: Earth to LEO - revisited - another direction

Re: ACES
I've seen a few things about this but it just seems potentially problematic.  I'd be more inclinde to look at things like in-air refuelling to top off the LOX tanks.  The performance isn't quite as great but it's an extension of a proven technology.

Is there any reason the DC-X couldn't get a cargo increase by combining it with the whole winged launcher strategy?  It seems like a logical way to go. 

Alternately, I'm still stumping for cheap, disposable SRBs to augment the DC-X cargo load.  I'm thinking of something like the little SRBs they put on Delta flights.  Nothing complicated, just a metal tube with fuel in it.  I'm still confused as to why SRBs can't be made to be purely disposable - a $1000 metal tube with some rubber and aluminum powder in it.  The shole multi-segment SRB design for the Shuttles just seems to be awrond-headed way to go about the whole thing.  SRBs are cheap and simple - capitalize on that fact.

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#35 2004-04-07 11:32:36

John Creighton
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From: Nova Scotia, Canada
Registered: 2001-09-04
Posts: 2,401
Website

Re: Earth to LEO - revisited - another direction

I don't know how much alumnium one should thorough away. How may ubundent sorces of it are there? What precentage comes from the amazon rain forst?


Dig into the [url=http://child-civilization.blogspot.com/2006/12/political-grab-bag.html]political grab bag[/url] at [url=http://child-civilization.blogspot.com/]Child Civilization[/url]

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#36 2004-04-07 14:38:34

GCNRevenger
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From: Earth
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Posts: 6,056

Re: Earth to LEO - revisited - another direction

Making SRBs is a little harder than you think... the trouble with making them THAT simple is that the thrust isn't uniform: the gasses that makes it go are released at the surface, so the higher the surface area, the higher the thrust.

Now, since the fuel is bonded to the inside of the engine tube and a hole is left open in the center, so that the fuel burns at the channel through the middle. As the fuel is consumed, a round channel in the center gets WIDER, so the surface area increases dramaticly and not be uniform at all. The way the Shuttle engines cope with this, is to made the channel down the center in a plus sign shape and to cut the fuel grain into sections permitting it to burn from the ends of each segment. This way, you get maximum power without much change in fuel surface area as the engine burns.

If you have a really REALLY simple SRB that was solid all the way through, and just lit it from the end, you'd have very low thrust from the small surface area, and more trouble with changes in center of mass as the burn worked its way up the tube.

And you can't just fill it with Al powder and light the fuse... you need an oxidizer too (Ammonium Perchlorate) and you need a binder to hold it all together (polybutadiene) to the engine. If the fuel were to crack or shift, the combustion rate would increase dramaticly... and kaboom.

The thing about adding them to any RLV is an increase in cost per launch... this is the biggie... if its possible to spend half billion on development to lower the clost per flight a few hundred thousand dollars, then its a good investment to make. When we do need a Shuttle-II or a DC-X, the term "RLV" should be taken literally and strictly. These aren't EELVs which won't fly but a few hundred times throughout the whole life of the design, i'm talking a vehicle in the >100 flights a year catagory. If you need a pair or a quartet of solids or a drop tank for each flight, that adds up FAST.

The DC-X vehicle itself still suffers from that nasty payload mass, and I doubt there is a good way around it without staging, which is undesireable. Mouting a miniature one on a big airplane doesn't make alot of sense to me either, where an airplane would be preferable.

I would like to know more about the ACES system before condemning it so quickly... adding inflight refueling vehicle costs, which will be signifigant for such a big plane to handle cryogenics, would add to the cost per flight signifigantly.

Although development money is an object, any reasonable technology that can drive down the cost per-flight is worthwhile.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#37 2004-04-07 15:00:09

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,936
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Re: Earth to LEO - revisited - another direction

Sorry to distract, but I just read this thread. The shuttle cost roughly $10,000 per pound, not per kg. Wait a minute, which way does that work out? About 2 years ago I made a list of heavy lift launch vehicles. In 2002 the shuttle was $19,643.5 per kg based on a full cargo bay and 200km orbit. [http://chapters.marssociety.org/winnipeg/files/lv.html]click here

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#38 2004-04-07 23:43:15

SBird
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Posts: 490

Re: Earth to LEO - revisited - another direction

Strange, according to your chart, the Shuttle weighs in at $5110/kg.  I've seen ~$10,000/kg being quoted for the Shuttle fairly often.  However, all the fixed costs, subsidization and other stuff make calculating the Shuttle cost per kg more of a voodoo science than anything else.

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#39 2004-04-08 07:39:07

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Earth to LEO - revisited - another direction

The only figure that we need to know about the price of a shuttle launch is "too much," both in human risk (it has killed more astronauts than any other space vehicle ever) and sheer cost per pound.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#40 2004-04-08 08:16:54

dicktice
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From: Nova Scotia, Canada
Registered: 2002-11-01
Posts: 1,764

Re: Earth to LEO - revisited - another direction

I hope insertion of the following news item might bring some relief from the preceeding gloomy posts regarding government run space programs:

Private spaceflight draws closer
By Dr David Whitehouse
BBC News Online science editor

The US Federal Aviation Authority (FAA) has granted a licence to Scaled Composites for a sub-orbital launch of their SpaceShipOne rocket-plane.
The license clears the way for an attempt on the X-prize later this year.
The X-prize of $10m (£5.4m) is for the first privately funded, non-governmental body that can launch a three-person craft into space twice in two weeks.
To claim the prize SpaceShipOne will have to reach an altitude of 100 km, the "official" boundary of space.

Space voyager
The FAA has given approval to Scaled Composites allowing it to expand its flight testing of SpaceShipOne - a privately-financed rocket plane to carry passengers into space.
Scaled Composites chief is Burt Rutan who was behind the design of Voyager - the first aircraft to fly non-stop around the world without refuelling.
SpaceShipOne and its carrier mothership, White Knight, were first shown to the public on 18 April 2003. Since then it has undergone extensive tests and during one powered flight it broke the sound barrier.
It uses a hybrid rocket motor that utilises a combination of liquid and solid-fuel.
SpaceShipOne has also undergone extensive glide flights, with the last one carried out last month.
Last December it was announced that multi-billionaire Paul Allen - co-founder of Microsoft - is a major investor in the project.
The X-prize was started in 1996 and has many groups registered. Analysts expect it to be claimed this year with Scaled Composites the favourite to do so.

Story from BBC NEWS:
[http://news.bbc.co.uk/go/pr/fr/-/2/hi/s … 610755.stm]http://news.bbc.co.uk/go/pr/fr/-/2/hi/s … 610755.stm
Published: 2004/04/08 10:25:15 GMT
© BBC MMIV

I really endorse this guy Rutan, and the fact that he comes from my old alma mater (California Polytechnic University) has hardly anything at all to do with it! :;):

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#41 2004-04-08 09:25:19

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
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Re: Earth to LEO - revisited - another direction

I think the novel The Rocket Company made two very clever suggestions for cheap flight to low earth orbit:

1. Use a two stage vehicle where the first stage launches straight up, so that it can fall straight back to the launch site and land. This means no first stage recovery costs and no complicated flyback system.

2. Use a vehicle that is cheap to reuse, but with a very small payload; they aimed at 5,000 pounds (2.25 tonnes). This takes advantage of the fact that the market is still small. Such a vehicle can fly 6-8 tourists to orbit at a time, so it's sized well for the tourist market (at fifty flights per year that's several hundred people, which is actually a pretty big initial market). Its a good size for low earth orbit satellite launches. If you want to launch stuff to the moon, you launch the same type of vehicle repeatedly to low earth orbit with fuel to refuel one of them, and use it to launch cargo to the moon. Two point two tonnes means inflatable habs have to be broken into small bits, but it would be doable. Most everything else can be launched in such scale: drillers, surface vehicles, supplies, etc.

A lot flights? So what, each one costs relatively little, and the vehicles have to make a lot of flights to be profitable. If a vehicle of this size could fly once a week, it could put 112 tonnes of cargo in low earth orbit per year. And the same vehicle can serve many markets, which is crucial for keeping down costs.

         -- RobS

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#42 2004-04-08 09:48:08

RobertDyck
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From: Winnipeg, Canada
Registered: 2002-08-20
Posts: 7,936
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Re: Earth to LEO - revisited - another direction

Strange, according to your chart, the Shuttle weighs in at $5110/kg.  I've seen ~$10,000/kg being quoted for the Shuttle fairly often.  However, all the fixed costs, subsidization and other stuff make calculating the Shuttle cost per kg more of a voodoo science than anything else.

The entire cargo bay of the Shuttle could be rented for commercial purposes for $142 million US dollars in 1992. I won't say that is the launch cost, in fact the cost in 1988 was $245M if you average the overhead cost over all flights, but the cost for an additional flight was $63M. The cost to rent the entire cargo bay hasn't been updated since 1992 because no one asked to use it. Now it's not available. So how do you calculate Shuttle cost? For the 2002 figure I took all Shuttle costs as described in the NASA budget and divided by 6 launches, then divided by the lift capacity to 200km for upgraded shuttles.

So, alternatives. Scaled Composites and SpaceX are companies to watch. I would like to see the X-43A developed into a shuttle, but that would take time.

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#43 2004-04-08 10:01:48

bolbuyk
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From: Utrecht, Netherlands
Registered: 2004-04-07
Posts: 178

Re: Earth to LEO - revisited - another direction

I think one of the most unfortunate aspects of the Shuttle is that it is a cargo-truck with drivers. Dividing cargo and persons has as benefit that cargo is not delayed when the shuttle is for any purpose grounded. Keep in mind that Magellan, Galileo and Ulysses were delayed by some years do to this fact.

A first stage falling down on the launch site? Is that really a good idea? I think the recovery is not more than 60 km from the Floridan coast and not very difficult.

More general, I ask myself if recovery of the SRB's is rational.
The same question I have by sending the heavy SSME's in LEO, where they do nothing, except requiring more proppellant for course-corrections.

The idea for Hermes, an proposed ESA-shuttle, had a back-compartment with air-lock and engines that would be jettisoned before reentry. The Russian Boeran does also not take it's main engines in LEO. They are fixed on the core-stage.

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#44 2004-04-08 10:07:39

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Earth to LEO - revisited - another direction

I don't think the Rocket Company has such a great idea...

Launching straight up isn't the most efficent way to fly, and will put more demands on the upper stage system.

Having it "fall straight back down" without a method for RTLS for soft landing like an airplane or DC-X, the recovery costs will not be trivial.

How are they going to reuse the upper stage? It is paramount that this come back down too, to the launch site.

Finally, that payload figure is just too small... the Iridium network and other LEO satelite constellations as a market have failed miserably, and that 5000lbs is just too small to do anything else with. Also, the cost, complexity, and inefficency of packing small amounts of somthing to be deliverd or assembled in orbit will outweigh the efficency of an RLV. The minimum mass I consider worthwhile is 10MT, and its unclear if anybody should bother with anything smaller than 20MT. 6-8 people into orbit and back for 5,000lbs is also a nonstarter.

The Rocket Company suffers from the perpetually smiling and helplessly optimistic outlook on spaceflight... its just not that easy.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#45 2004-04-08 11:13:31

Euler
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From: Corvallis, OR
Registered: 2003-02-06
Posts: 922

Re: Earth to LEO - revisited - another direction

The Rocket Company vehicle would not be very good for transporting large pieces of cargo, but it is excellent for transporting people.  As long as there is a space station for them to go to, it could be a very successful spacecraft.  Their vehicle is similar in size and function the Kliper that the Russians are working on.

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#46 2004-04-08 11:28:37

SBird
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Registered: 2004-03-10
Posts: 490

Re: Earth to LEO - revisited - another direction

GCNRevenger - I am aware of the difficulties in maintaining proper burn rate on an SRB, however, the engineering difficulties of a proper propellant hole cross section are pretty trivial in comaprison, say, to designing a high pressure fuel/oxidizer turbopump or lifting reentry body.  It might even be a good idea to use off-the shelf hardware.  The Delta IV uses no less than 9 SRBs and has a great operational track record.  Obviously, the individual SRB reliability is the 9th root of the overall SRB performance on that launcher.  The engineering work has already been done.  The SRBs are most likely quite cheap in reagards to the rest of the system.

It would therefore seem logical to design a DC-X vehicle to be able to structurally accomodate the stresses of several SRB tiedown points.  The standard cost of a 10 MT launch these days is about $50 million.  If we want to hit the target goal of $500/kg, our launch costs have to be $5million  or less per launch.  Fuel costs and refurbishing shouldn't take more than a few million and figure an amortized million per launch in personnel costs.  As long as you can make a pack of SRBs for under a couple million, you're in business since you'll be increasing the cargo capacity.

The SRBs can even be optional.  Say, 10 MT to orbit w/o SRBs and 15 MT to orbit with.  If crew are being boosted, there's no reason to use that extra cargo capacity and added failure risk of the SRBs.  If cargo is going up, the customer has the choise of the 10 MT load at, say, $500/kg or the 15 MT load at $600/kg.


As for the plane-based 1st stage, I was envisioning a full-sized DC-X as the second stage.  A 747 has a takeoff weight of 500 tons.  That's a LOT of capacity.  Gut the hull and revamp it as a launch cradle and you're ready to carry a lot of rocket up into the air.  Of course, things like mach 6 performance don't work in that case but a mach 6 airplane requires a massive R&D effort regardless of how much cargo it carries.

I conceed that an air-gathering system might not be too difficult - the Soviets worked on an airbreather ICBM - but I fail to see how it could be anywhere as light or simple as a refueling interface and a couple of insulated pipes.  I know that Zubron's spinoff company, Pioneer areospace is useing the LOX in-air refuelling and claim that it presents no big challenges.  IIRC, the Air Force tinkered around with the idea for a while.

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#47 2004-04-08 12:21:07

Palomar
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From: USA
Registered: 2002-05-30
Posts: 9,734

Re: Earth to LEO - revisited - another direction

I hope insertion of the following news item might bring some relief from the preceeding gloomy posts regarding government run space programs:

Private spaceflight draws closer
By Dr David Whitehouse
BBC News Online science editor

The US Federal Aviation Authority (FAA) has granted a licence to Scaled Composites for a sub-orbital launch of their SpaceShipOne rocket-plane.

*Hopefully this isn't getting off-topic.  Just now [http://www.space.com/missionlaunches/sp … 40408.html]saw this, Breaking News, at space.com.

Completed its 2nd "rocket-powered test flight."  Reached altitude of 105,000 ft.

--Cindy


We all know [i]those[/i] Venusians: Doing their hair in shock waves, smoking electrical coronas, wearing Van Allen belts and resting their tiny elbows on a Geiger counter...

--John Sladek (The New Apocrypha)

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#48 2004-04-08 15:23:06

SBird
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Registered: 2004-03-10
Posts: 490

Re: Earth to LEO - revisited - another direction

Carmack and those Canadians had better step up their pace if they want to even have a slim chance at getting the prize.  105,000 feet is about 1/3 of the X-prize altitude.

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#49 2004-04-09 09:01:30

GCNRevenger
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From: Earth
Registered: 2003-10-14
Posts: 6,056

Re: Earth to LEO - revisited - another direction

I've got doubts that the SRBs would be worth the trouble... they can't be all that cheap for high quality ones that won't destroy the multibillion dollar vehicle, and then there is the expense of handing/mating them/etc. It would also detract one of the DC-X or any 100% RLV's advantage that you don't have to launch over water/desert to keep spent stages from falling on people.

In the grand scheme of things, the extra cost of those SRBs per-flight will really start to add up, especially if there are loads of flights, where not having them becomes a major economic advantage.

Finally, I think flying any RLV will be expensive enough as it is, and I am not sure that a vehicle with SRBs will meet or beat the cost-per-kilo needs, and limit future improvements.

Oh yes, and the DC-I, the vehicle that the DC-X was going to be a phase-I prototype for, weighs in at 470MT sans payload, and it would be 40m long and 10m wide... I don't know if it would fit on a 747! Not to mention, the advantage of airlaunching a rocket like that would not likly be so great.

The nice thing about ACES or other onboard fuel plant is, it saves you having to fly another vehicle. It does increase the cost of making the RLV, but it reduces operational costs down the road, the ultimate goal. Simple isn't better by default.


[i]"The power of accurate observation is often called cynicism by those that do not have it." - George Bernard Shaw[/i]

[i]The glass is at 50% of capacity[/i]

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#50 2004-04-09 11:14:46

RobS
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From: South Bend, IN
Registered: 2002-01-15
Posts: 1,701
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Re: Earth to LEO - revisited - another direction

By "straight down" The Rocket Company doesn't mean straight onto the launch pad, but landing nearby. They postulated a vertical landing under rocket power (or possibly using vertically oriented turbojets; the novel hasn't decided which to use yet). The alternative is a ballistic flight with a delta-v of about 5,000 mph that brings down the first stage several thousand miles down range. Then you have to fly the stage back or haul it back by ship. The shuttle's solids don't come down just a few miles off the coast; they come down way out in the Atlantic.

The second stage is reusable as well; of course. It has a heat shield and comes down from orbit. The first stage has a low enough delta-v not to need much thermal protection.

I don't agree that you need a minimum launch mass of 10 or 20 metric tonnes. Go ahead and design such a vehicle, then try to sell 50 launches a year. There isn't enough demand for that many launches. To make a vehicle cheap, you need to spread the design costs out among a dozen or so vehicles, and you need to fly those vehicles a lot to make them  economic. If you have a payload of ten metric tonnes and a flight frequency of once per week, you have to sell 500 metric tonnes per year; if you have ten vehicles, 5,000 metric tonnes per year. But start with a small vehicle, design it, prove the technology, lower launch costs, build demand, THEN put out the updated version of the shuttle a decade later with 5 metric tonne or 10 metric tonne payload; get the picture? The technology has to be as simple as possible to keep costs down and the flight frequency has to be high to cover the cost of the maintenance team. That makes sense to me.

Yes, you can't launch something really big with it. Maybe in a decade the second version will, but you can't pay for the bigger version initially. So big things go up in old, EELVs for another decade or so. I bet with careful design, that won't be too many objects.

As for on-orbit assembly: if it only costs a few hundred bucks per pound to put people and their supplies in orbit, it's not that expensive to put up a few more people to do the assembly!

        -- RobS

P.S. an hour later: Someone noted that the vertical first stage trajectory plus horizontal second stage trajectory puts the second stage under more stress; so what? The added delta-v to the system is probably only a few hundred miles per hour; it isn't much. The point is to create a cheap system to get to orbit. It's cheaper to do it this way than to create a single stage to orbit (very large, lots of structure to accelerate to orbital speed and then shield from reentry heating) or a diagonal launch (major first stage recovery issues to resolve).

Also, keep in mind that the small vehicle, the smaller the development and construction cost. Start small, keep the prices manageable, build the market, plow the profit into bigger vehicles.

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