Author Topic: Another look at SSTO.  (Read 7405 times)

Offline DiggyCoxwell

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Another look at SSTO.
« on: 04/30/2010 02:26 AM »
  Single-Stage To Orbit still appears out of reach
to many engineers, with the exception of the hypothetical
HOTOL/Skylon concepts.

But Project Score in December, 1958, using a 1-1/2 stage Atlas
booster, may have showed how it can be done by a conventional booster; at least for a small payload on a proof-of-concept
launch-flight.
   The original Atlas of course was basically a stainless-steel 'balloon'
with three rocket motors at launch.
 Too generic a definition, huh?
Maybe.
 The original Atlas' stainless steel shell was no where thicker
than a quarter, and on average almost as thin as a dime. 

The Project Score Atlas weighed about 182,000 Ibs fully loaded;
and was about 8600 Ibs empty in orbit, minus the 150 Ib payload.
Minus the weight of the sustainer rocket motor (1010Ibs?)
Minus the weight of its pumps, pressurizing tanks, vernier rockets and fuel tanks, transistorized avionics and inertial guidance system
the stainless steel shell would have probably been around
6,500Ibs weight, give or take a couple of hundred pounds.
 
Thing is?..There was no epoxy-kevlar, nor graphite-epoxy composite
back then. There was no lightweight laser gyroscopic IGS, nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).
And the Project Score Atlas did not have primary engines that were
throttled by avionics.
   So how much weight could have been saved by replacing the thin
stainless steel shell with a teflon-coated epoxy-kevlar or epoxy-graphite
shell?
2000Ibs saved?
4000Ibs?...I think this value is possible.
How many pounds would have been saved by replacing the steel in the Atlas rocket motors with titanium? You do the math.
So a modernized Project Score Atlas could become an SSTO vehicle capable of putting a small payload into orbit, even if it meant hauling
all three of its primary motors into orbit?
What do you think?
 

 
 
« Last Edit: 04/30/2010 02:27 AM by DiggyCoxwell »

Offline Jorge

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Re: Another look at SSTO.
« Reply #1 on: 04/30/2010 02:30 AM »
  Single-Stage To Orbit still appears out of reach
to many engineers, with the exception of the hypothetical
HOTOL/Skylon concepts.

But Project Score in December, 1958, using a 1-1/2 stage Atlas
booster, may have showed how it can be done by a conventional booster; at least for a small payload on a proof-of-concept
launch-flight.
   The original Atlas of course was basically a stainless-steel 'balloon'
with three rocket motors at launch.
 Too generic a definition, huh?
Maybe.
 The original Atlas' stainless steel shell was no where thicker
than a quarter, and on average almost as thin as a dime. 

The Project Score Atlas weighed about 182,000 Ibs fully loaded;
and was about 8600 Ibs empty in orbit, minus the 150 Ib payload.
Minus the weight of the sustainer rocket motor (1010Ibs?)
Minus the weight of its pumps, pressurizing tanks, vernier rockets and fuel tanks, transistorized avionics and inertial guidance system
the stainless steel shell would have probably been around
6,500Ibs weight, give or take a couple of hundred pounds.
 
Thing is?..There was no epoxy-kevlar, nor graphite-epoxy composite
back then. There was no lightweight laser gyroscopic IGS, nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).
And the Project Score Atlas did not have primary engines that were
throttled by avionics.
   So how much weight could have been saved by replacing the thin
stainless steel shell with a teflon-coated epoxy-kevlar or epoxy-graphite
shell?
2000Ibs saved?
4000Ibs?...I think this value is possible.
How many pounds would have been saved by replacing the steel in the Atlas rocket motors with titanium? You do the math.
So a modernized Project Score Atlas could become an SSTO vehicle capable of putting a small payload into orbit, even if it meant hauling
all three of its primary motors into orbit?
What do you think?
 

 
 

Yes, SSTO ELV technically could have been achieved long ago. It hasn't been pursued because it makes no economic sense. SSTO is suboptimal for payload mass fraction and for ELV you care about that. You don't care about it as much for RLVs because you amortize the vehicle costs over many flights.
JRF

Offline Jim

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Re: Another look at SSTO.
« Reply #2 on: 04/30/2010 02:45 AM »
 
   So how much weight could have been saved by replacing the thin
stainless steel shell with a teflon-coated epoxy-kevlar or epoxy-graphite
shell?


None.  Just being a composites doesn't mean it will save weight.  A composite tank can not be made the same way as the balloon tank

Online kevin-rf

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Re: Another look at SSTO.
« Reply #3 on: 04/30/2010 02:45 AM »
Here is something to chew on,

Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.

Pure fantasy, but still interesting.

Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.
« Last Edit: 04/30/2010 02:46 AM by kevin-rf »
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Offline Jim

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Re: Another look at SSTO.
« Reply #4 on: 04/30/2010 02:47 AM »

  nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).


Nor are they any now. 

Offline jongoff

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Re: Another look at SSTO.
« Reply #5 on: 04/30/2010 04:38 AM »
Here is something to chew on,

Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.

Pure fantasy, but still interesting.

Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.

With balloon tanks and a modern TAN-like engine, I think you could do SSTO, possibly with enough margin to make it fully reusable.  A modern TAN engine, done right could have much better vacuum performance than the Atlas sustainer, without having to carry the mass of the booster engines even for the first bit of the flight.

~Jon

Offline TrueBlueWitt

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Re: Another look at SSTO.
« Reply #6 on: 04/30/2010 04:55 AM »
Here is something to chew on,

Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.

Pure fantasy, but still interesting.

Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.

With balloon tanks and a modern TAN-like engine, I think you could do SSTO, possibly with enough margin to make it fully reusable.  A modern TAN engine, done right could have much better vacuum performance than the Atlas sustainer, without having to carry the mass of the booster engines even for the first bit of the flight.

~Jon

Sounds great going up..  not sure how you get it back down?  Balloon tanks and heat dissipation/shielding on re-entry.. hmm.. what are your thoughts there Jon? How much mass would you chew up to make it reusable? 
« Last Edit: 04/30/2010 04:56 AM by TrueBlueWitt »

Offline gbaikie

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Re: Another look at SSTO.
« Reply #7 on: 04/30/2010 05:22 AM »
  Single-Stage To Orbit still appears out of reach
to many engineers, with the exception of the hypothetical
HOTOL/Skylon concepts.

But Project Score in December, 1958, using a 1-1/2 stage Atlas
booster, may have showed how it can be done by a conventional booster; at least for a small payload on a proof-of-concept
launch-flight.
   The original Atlas of course was basically a stainless-steel 'balloon'
with three rocket motors at launch.

"Monocoque is a construction technique that supports structural load by using an object's exterior, as opposed to using an internal frame or truss that is then covered with a non-load-bearing skin or coachwork. The word monocoque comes from the Greek for single (mono) and French for shell (coque). The technique may also be called structural skin, stressed skin, unit body, unibody, unitary construction, or Body Frame Integral (BFI).
...
Various rockets  also use a flight pressure-stabilized monocoque design, including the Atlas II  and Falcon I."
http://en.wikipedia.org/wiki/Monocoque

<snip>


"How many pounds would have been saved by replacing the steel in the Atlas rocket motors with titanium? You do the math."

Not much.

"So a modernized Project Score Atlas could become an SSTO vehicle capable of putting a small payload into orbit, even if it meant hauling
all three of its primary motors into orbit?
What do you think?"

How do it get down from orbit?

In one piece, I mean.

The problem with rockets in general, isn't the technology. It's economics and politics.

How much does it cost to build one rocket? How much does it cost to build a thousand rockets?
To build most rockets it should cost somewhere around 1 million dollars- it doesn't. Though you can buy a rocket for about 2 million dollars, though if spending say 10 million dollar just on the engines it's going to cost more. The rocket engine is about the simplest engine in existence- though this doesn't mean one can't make them extremely complicated.

People will furiously argue that you couldn't possibility buy any kind of rocket that would reach orbit for 2 million dollars. Whatever, say 5 million or 10 million dollars.

Now you bought the 10 million dollar rocket, how much does it cost to launch it?
Maybe you get the launch for free- because you know the right people, or the right people simply wish to be helpful- it's in their interests in some way.
But how much does it actually costs to launch rocket? How much it cost to buy or lease a launch pad? How many people do you need to fuel the rocket and put whatever satellite on top of it. How people need control the launch and deal with all the stuff you need to put that thing into orbit?
All this stuff, can easily cost more than just cost of the rocket.

Now, As recall the Russians, were leasing their launch facilities from their former "satellite country" and they are paying about 100 million a year for that privilege. That kind of overhead can drive up the price rocket launches- and if you are get 20 million per Soyuz seat, that is going help the poor Russians pay for this.
And does help explain why the Russians could have some interest in using the French launch site- though no idea how much that will cost per launch- probably nothing to the Russian- they instead just get paid to provide the rockets. But there is still a cost to someone for that launch site- perhaps the French tax payer are subsidizing some of it.

But no one going to give specific prices, because that is rude or something- and generally makes it harder for corruption in general.
 

 
 

Offline Rhyshaelkan

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Re: Another look at SSTO.
« Reply #8 on: 04/30/2010 06:02 AM »
Meh, I think we are going the wrong way with space. Stick to our costly launches. Make space industry. Build our CNT elevator. Blast the cost.

If anything, stop the exploring and focus on something more economically tangible.
I am not a professional. Just a rational amateur dreaming of mankind exploiting the universe.

Offline Jim

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Re: Another look at SSTO.
« Reply #9 on: 04/30/2010 06:09 AM »
Build our CNT elevator.


Tangible? how about not even feasible.
« Last Edit: 04/30/2010 06:12 AM by Jim »

Offline jongoff

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Re: Another look at SSTO.
« Reply #10 on: 04/30/2010 06:21 AM »
Here is something to chew on,

Making a few assumptions about TAN,, the same thrust as the the stage and a half plus sustainer could be produced with just the sustainer in about the same mass as the sustainer.

Pure fantasy, but still interesting.

Do not forget, the Atlas also placed itself with the much heavier mercury capsule in orbit.

With balloon tanks and a modern TAN-like engine, I think you could do SSTO, possibly with enough margin to make it fully reusable.  A modern TAN engine, done right could have much better vacuum performance than the Atlas sustainer, without having to carry the mass of the booster engines even for the first bit of the flight.

~Jon

Sounds great going up..  not sure how you get it back down?  Balloon tanks and heat dissipation/shielding on re-entry.. hmm.. what are your thoughts there Jon? How much mass would you chew up to make it reusable?

You'd probably chew up a decent amount of mass making it reusable, but with the lower propulsion system mass, and the higher mission averaged Isp, I think the concept has a reasonable chance of closing.  Honestly though, I'm more interested in TSTO concepts at the moment--they're a lot easier to close.

~Jon

Offline Steven Pietrobon

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Re: Another look at SSTO.
« Reply #11 on: 04/30/2010 06:35 AM »
Here's one way to design a SSTO vehicle that I believe will work. Build a long cylindrical tank with a common bulkhead. Add wings, thermal protection and six SSME sized engines at the base using 2130 t of LOX/RP-1 (and definitely not LOX/LH2). Add the payload to the side, light the candle and in about seven minutes you will have put a 34.8 t payload into an 80x185 km orbit. Vehicle dry mass is 139.5 t. The payload does a small burn at apogee to go into orbit. The vehicle performs a once-around maneuver, returning to the launch site after about 90 minutes. Using more exotic RP-X2 (quadracyclene) fuel increases payload mass by 67.5% to 58.3 t. Here's a paper I wrote about it.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline spacenut

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Re: Another look at SSTO.
« Reply #12 on: 04/30/2010 02:52 PM »
The only cost effective way I see is to build the plug nozzle engine on a "Rombus" type booster as designed back in the '60's.  Or you could build a flyback booster with a plug nozzle second stage to retrieve it. 

Offline DiggyCoxwell

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Re: Another look at SSTO.
« Reply #13 on: 04/30/2010 05:33 PM »

  nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).


Nor are they any now. 

Then I chose the right webpage category: "Advanced Concepts";
at least advanced concepts involving titanium metallurgy, and titanium
machining (Yes, I am aware that titanium is a difficult metal to machine.)

Offline Arthur

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Re: Another look at SSTO.
« Reply #14 on: 04/30/2010 05:34 PM »
Here's one way to design a SSTO vehicle that I believe will work. Build a long cylindrical tank with a common bulkhead. Add wings, thermal protection and six SSME sized engines at the base using 2130 t of LOX/RP-1 (and definitely not LOX/LH2). Add the payload to the side, light the candle and in about seven minutes you will have put a 34.8 t payload into an 80x185 km orbit. Vehicle dry mass is 139.5 t. The payload does a small burn at apogee to go into orbit. The vehicle performs a once-around maneuver, returning to the launch site after about 90 minutes. Using more exotic RP-X2 (quadracyclene) fuel increases payload mass by 67.5% to 58.3 t. Here's a paper I wrote about it.

Past spaceplane designs ran into issues with becoming too tail heavy during reentry. Have you looked into avoiding that issue? [I only skimmed your paper, but the seven SSMEs in the tail and large empty tanks in the front reminded me of the issue.]
« Last Edit: 04/30/2010 05:40 PM by Arthur »

Offline strangequark

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Re: Another look at SSTO.
« Reply #15 on: 04/30/2010 05:51 PM »

  nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).


Nor are they any now. 

Then I chose the right webpage category: "Advanced Concepts";
at least advanced concepts involving titanium metallurgy, and titanium
machining (Yes, I am aware that titanium is a difficult metal to machine.)


The point is more that existing engines are not substantially lighter weight than the LR89 used on the Atlas D. It had a T/W ratio of 120, compared to about 100 for the RS-27, which was a much more recent kerosene engine (of similar thrust rating). Even the venerable NK-33 only managed 135. So "heavy by today's standards" is an unfounded, and in fact false, statement
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Offline jongoff

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Re: Another look at SSTO.
« Reply #16 on: 04/30/2010 07:26 PM »

  nor were there lightweight titanium rocketmotors (The 1958 Atlas had special steel alloy or stainless steel rocket motors; heavy by today's standards).


Nor are they any now. 

Then I chose the right webpage category: "Advanced Concepts";
at least advanced concepts involving titanium metallurgy, and titanium
machining (Yes, I am aware that titanium is a difficult metal to machine.)


The point is more that existing engines are not substantially lighter weight than the LR89 used on the Atlas D. It had a T/W ratio of 120, compared to about 100 for the RS-27, which was a much more recent kerosene engine (of similar thrust rating). Even the venerable NK-33 only managed 135. So "heavy by today's standards" is an unfounded, and in fact false, statement

Not to mention that if I were looking for a lighter material to do the chamber out of, aluminum is probably a better choice than titanium--much better thermoconductivity, much easier to work with, lower density, etc.

But I'm biased.

~Jon

Offline hkhenson

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Re: Another look at SSTO.
« Reply #17 on: 04/30/2010 08:49 PM »
Here's one way to design a SSTO vehicle that I believe will work. Build a long cylindrical tank with a common bulkhead. Add wings, thermal protection and six SSME sized engines at the base using 2130 t of LOX/RP-1 (and definitely not LOX/LH2). Add the payload to the side, light the candle and in about seven minutes you will have put a 34.8 t payload into an 80x185 km orbit. Vehicle dry mass is 139.5 t. The payload does a small burn at apogee to go into orbit. The vehicle performs a once-around maneuver, returning to the launch site after about 90 minutes. Using more exotic RP-X2 (quadracyclene) fuel increases payload mass by 67.5% to 58.3 t. Here's a paper I wrote about it.


2130 + 139.5 + 34.8 = 2304.3
139.5 + 34.8 = 174.3
mass ratio 2304.3/174.3 is 13.2

2.58 x Ve =9 or Ve is 3.4 km/sec or ISP of 360 seconds

The F1A engine was 265 seconds.  What engine are you proposing?

Structure fraction 139.5/2304.3 is 6.05%

You seem to be thinking about reusable since you mention it coming back to the launch pad in 90 minutes.

I am not a rocket engineer, just an EE with an interest.  But I have asked Gary Hudson whose opinion is that the structure fraction for reusable needs to be 15% or more.

That's about the structure fraction of a Skylon.

How do you get it to 6%?

Best wishes,

Keith Henson

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Re: Another look at SSTO.
« Reply #18 on: 04/30/2010 09:05 PM »
Here's one way to design a SSTO vehicle that I believe will work. Build a long cylindrical tank with a common bulkhead. Add wings, thermal protection and six SSME sized engines at the base using 2130 t of LOX/RP-1 (and definitely not LOX/LH2). Add the payload to the side, light the candle and in about seven minutes you will have put a 34.8 t payload into an 80x185 km orbit. Vehicle dry mass is 139.5 t. The payload does a small burn at apogee to go into orbit. The vehicle performs a once-around maneuver, returning to the launch site after about 90 minutes. Using more exotic RP-X2 (quadracyclene) fuel increases payload mass by 67.5% to 58.3 t. Here's a paper I wrote about it.


2130 + 139.5 + 34.8 = 2304.3
139.5 + 34.8 = 174.3
mass ratio 2304.3/174.3 is 13.2

2.58 x Ve =9 or Ve is 3.4 km/sec or ISP of 360 seconds

The F1A engine was 265 seconds.  What engine are you proposing?

Structure fraction 139.5/2304.3 is 6.05%

You seem to be thinking about reusable since you mention it coming back to the launch pad in 90 minutes.

I am not a rocket engineer, just an EE with an interest.  But I have asked Gary Hudson whose opinion is that the structure fraction for reusable needs to be 15% or more.

That's about the structure fraction of a Skylon.

How do you get it to 6%?

Best wishes,

Keith Henson

Structural fraction sort of depends strongly on fuel density, doesn't it? I mean, it's reentering and flying back (or just gliding or splashing or plopping, like a Soyuz) empty or almost empty, which is the only thing that a reusable does that a launch vehicle doesn't. In those circumstances, the density of the fuel doesn't put extra loads on the airframe beyond launch, and launch vehicles with denser fuels tend to have higher mass fractions. Using a dense fuel and balloon tanks should allow you to get really high wet/dry ratios, even for reusable. Heck, the centaur v-1 has about a wet/dry ratio of 11, and it's hydrolox.

A kerolox one (or some more exotic dense propellant) could probably do better with balloon tanks, since kerolox is about three times denser than hydrolox. Mix the two in a TAN, and you can get both the high-thrust needed (and very high thrust/weight) at first, then the high-ISP needed later. That's how it's possible.
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Offline hkhenson

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Re: Another look at SSTO.
« Reply #19 on: 04/30/2010 10:37 PM »
  Single-Stage To Orbit still appears out of reach
to many engineers, with the exception of the hypothetical
HOTOL/Skylon concepts.

<snip>

What do you think?
 

It's all about exhaust velocity.  I worked the Skylon design backwards and it gets a remarkable 10.5 km/sec equivalent exhaust velocity until it runs out of air.  (After that it isn't any better than SSME.)

Even so it only puts about 12 tons in LEO.  (The vehicle mass is ~50 tons, about 18% of takeoff mass.)

SSME performance and 15% structural mass puts a pointless zero payload in orbit.

It wasn't possible to think about better than chemical exhaust velocities before big solid state lasers came along, but it is now.  The problem with lasers is that you want to run them all the time (otherwise the capital cost is too high).  Also you have a limited window in which to accelerate to orbital velocity.  This means about 4 launches an hour.  For 200 tons per hour in LEO it came out to need $60 B in lasers starting with a Skylon type vehicle.  I don't think Skylon would scale to a vehicle 1/10th as large (area to volume scaling problems) but if it could, you could get a system that would deliver 20 tons per hour to LEO in 5 ton payloads.

If any of you can think of something useful to do with this, it could probably get down to under $100,000 per launch or $20/kg to LEO, $40/kg to GEO.

The physics and economics analysis is straightforward.

Keith




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