An SSTO as "God and Robert Heinlein intended".

RGClark · Posted on: Thu Dec 27, 2012 7:53 am

RGClark wrote:

No, SSTO is not a four-letter word, though it is sometimes treated that way by those in the industry.
I've been arguing that SSTO's are actually easy because how to achieve them is perfectly obvious: use the most weight optimized stages and most Isp efficient engines at the same time, i.e., optimize both components of the rocket equation. But I've recently found it's even easier than that! It turns out you don't even need the engines to be of particularly high efficiency.
SpaceX is moving rapidly towards testing its Grasshopper scaled-down version of a reusable VTVL Falcon 9 first stage:

Reusable rocket prototype almost ready for first liftoff.
BY STEPHEN CLARK
SPACEFLIGHT NOW
Posted: July 9, 2012
http://www.spaceflightnow.com/news/n1207/10grasshopper/

SpaceX will be duplicating in this what the DC-X accomplished in the early 90's. The DC-X was a scaled down, low altitude test vehicle for a full-scale SSTO VTVL vehicle. So could the full-sized Falcon 9 first stage act as a VTVL SSTO?
SpaceX deserves kudos for achieving a highly weight optimized Falcon 9 first stage at a 20 to 1 mass ratio. However, the Merlin 1C engine has an Isp no better than the engines we had in the early sixties at 304 s, and the Merlin 1D is only slightly better on the Isp scale at 310 s. This is well below the highest efficiency kerosene engines (Russian) we have now whose Isp's are in the 330's. So I thought that closed the door on the Falcon 9 first stage being SSTO.
However, I was surprised when I did the calculation that because of the Merlin 1D's lower weight the Falcon 9 first stage could indeed be SSTO. I'll use the Falcon 9 specifications estimated by GW Johnson, a former rocket engineer, now math professor:

WEDNESDAY, DECEMBER 14, 2011
Reusability in Launch Rockets.
http://exrocketman.blogspot.com/2011/12 ... ckets.html

The first stage propellant load is given as 553,000 lbs, 250,000 kg, and the dry weight as 30,000 lbs, 13,600 kg...

I'll calculate now the payload for the first stage of the new version of
the Falcon 9, version 1.1. The Falcon Heavy will use this version's
first stage for its core stage and side boosters. SpaceX expects the
Falcon 9 v1.1 to be ready by the end of the year.

Elon Musk has said version 1.1 will be about 50% longer:

Q&A with SpaceX founder and chief designer Elon Musk.
BY STEPHEN CLARK
SPACEFLIGHT NOW
Posted: May 18, 2012
http://www.spaceflightnow.com/falcon9/003/120518musk/

I'll assume this is coming from 50% larger tanks. This puts the
propellant load now at 375,000 kg. Interestingly SpaceX says the side
boosters on the Falcon Heavy will have a 30 to 1 mass ratio. This
improvement is probably coming from the fact it is using the lighter
Merlin 1D engines, and because scaling up a rocket actually improves
your mass ratio, and also not having to support the weight of an upper
stage and heavy payload means it can be made lighter.

So I'll assume for this SSTO version of the Falcon 9 v1.1 the mass
ratio is 30 to 1, which makes the dry mass 13 mT.

To estimate the payload I'll use the payload estimation program of
Dr. John Schilling:

Launch Vehicle Performance Calculator.
http://www.silverbirdastronautics.com/LVperform.html

It actually gives a range of likely values of the payload. But I've found
the midpoint of the range it specifies is a reasonably accurate estimate
to the actual payload for known rockets.

Input the vacuum values for the thrust in kilonewtons and Isp in
seconds. The program takes into account the sea level loss. SpaceX
gives the Merlin 1D vacuum thrust as 161,000 lbs and vacuum Isp
as 311 s:

FALCON 9 OVERVIEW.
http://www.spacex.com/falcon9.php

For the 9 Merlins this is a thrust of 9*161,000lb*4.46N/lb = 6,460
kN. Use the default altitude of 185 km and select the Cape Canaveral
launch site, with a 28.5 degree orbital inclination to match the
Cape's latitude.

Input the dry mass of 13,000 kg and propellant mass of 375,000 kg.
The other options I selected are indicated here:

Then it gives an estimated 7,564 kg payload mass:

===================================================
Launch Vehicle: User-Defined Launch Vehicle
Launch Site: Cape Canaveral / KSC
Destination Orbit: 185 x 185 km, 28 deg
Estimated Payload: 7564 kg
95% Confidence Interval: 3766 - 12191 kg
===================================================

This may be enough to launch the Dragon capsule, depending on the mas
of the Launch Abort System (LAS).

Bob Clark

Experimental Private Rocket Makes Highest Test Hop Yet.
by Miriam Kramer, SPACE.com Staff WriterDate: 26 December 2012 Time:
11:04 AM ET
"In the latest test at SpaceX's proving grounds in MacGregor, Texas,
the Grasshopper rocket flew for 29 seconds and reached a height of
more than 130 feet (40 meters). A video of the Grasshopper test flight
shows the rocket soaring up into the Texas sky, then smoothly
descending to land on four spindly legs."
http://www.space.com/19039-spacex-priva ... -test.html

With reduced weight of the Merlin 1D engine while at increased efficiency, the Falcon 9 v1.1 first stage will have SSTO capability. Then ironically Elon is emulating the original purpose of the DC-X program in testing the Grasshopper VTVL stage, without realizing it.

Bob Clark

Author	Message
RGClark Space Walker Joined: Sat Jul 01, 2006 12:18 am Posts: 213	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Thu Dec 27, 2012 7:53 am RGClark wrote: RGClark wrote: No, SSTO is not a four-letter word, though it is sometimes treated that way by those in the industry. I've been arguing that SSTO's are actually easy because how to achieve them is perfectly obvious: use the most weight optimized stages and most Isp efficient engines at the same time, i.e., optimize both components of the rocket equation. But I've recently found it's even easier than that! It turns out you don't even need the engines to be of particularly high efficiency. SpaceX is moving rapidly towards testing its Grasshopper scaled-down version of a reusable VTVL Falcon 9 first stage: Reusable rocket prototype almost ready for first liftoff. BY STEPHEN CLARK SPACEFLIGHT NOW Posted: July 9, 2012 http://www.spaceflightnow.com/news/n1207/10grasshopper/ SpaceX will be duplicating in this what the DC-X accomplished in the early 90's. The DC-X was a scaled down, low altitude test vehicle for a full-scale SSTO VTVL vehicle. So could the full-sized Falcon 9 first stage act as a VTVL SSTO? SpaceX deserves kudos for achieving a highly weight optimized Falcon 9 first stage at a 20 to 1 mass ratio. However, the Merlin 1C engine has an Isp no better than the engines we had in the early sixties at 304 s, and the Merlin 1D is only slightly better on the Isp scale at 310 s. This is well below the highest efficiency kerosene engines (Russian) we have now whose Isp's are in the 330's. So I thought that closed the door on the Falcon 9 first stage being SSTO. However, I was surprised when I did the calculation that because of the Merlin 1D's lower weight the Falcon 9 first stage could indeed be SSTO. I'll use the Falcon 9 specifications estimated by GW Johnson, a former rocket engineer, now math professor: WEDNESDAY, DECEMBER 14, 2011 Reusability in Launch Rockets. http://exrocketman.blogspot.com/2011/12 ... ckets.html The first stage propellant load is given as 553,000 lbs, 250,000 kg, and the dry weight as 30,000 lbs, 13,600 kg... I'll calculate now the payload for the first stage of the new version of the Falcon 9, version 1.1. The Falcon Heavy will use this version's first stage for its core stage and side boosters. SpaceX expects the Falcon 9 v1.1 to be ready by the end of the year. Elon Musk has said version 1.1 will be about 50% longer: Q&A with SpaceX founder and chief designer Elon Musk. BY STEPHEN CLARK SPACEFLIGHT NOW Posted: May 18, 2012 http://www.spaceflightnow.com/falcon9/003/120518musk/ I'll assume this is coming from 50% larger tanks. This puts the propellant load now at 375,000 kg. Interestingly SpaceX says the side boosters on the Falcon Heavy will have a 30 to 1 mass ratio. This improvement is probably coming from the fact it is using the lighter Merlin 1D engines, and because scaling up a rocket actually improves your mass ratio, and also not having to support the weight of an upper stage and heavy payload means it can be made lighter. So I'll assume for this SSTO version of the Falcon 9 v1.1 the mass ratio is 30 to 1, which makes the dry mass 13 mT. To estimate the payload I'll use the payload estimation program of Dr. John Schilling: Launch Vehicle Performance Calculator. http://www.silverbirdastronautics.com/LVperform.html It actually gives a range of likely values of the payload. But I've found the midpoint of the range it specifies is a reasonably accurate estimate to the actual payload for known rockets. Input the vacuum values for the thrust in kilonewtons and Isp in seconds. The program takes into account the sea level loss. SpaceX gives the Merlin 1D vacuum thrust as 161,000 lbs and vacuum Isp as 311 s: FALCON 9 OVERVIEW. http://www.spacex.com/falcon9.php For the 9 Merlins this is a thrust of 9161,000lb4.46N/lb = 6,460 kN. Use the default altitude of 185 km and select the Cape Canaveral launch site, with a 28.5 degree orbital inclination to match the Cape's latitude. Input the dry mass of 13,000 kg and propellant mass of 375,000 kg. The other options I selected are indicated here: Then it gives an estimated 7,564 kg payload mass: =================================================== Launch Vehicle: User-Defined Launch Vehicle Launch Site: Cape Canaveral / KSC Destination Orbit: 185 x 185 km, 28 deg Estimated Payload: 7564 kg 95% Confidence Interval: 3766 - 12191 kg =================================================== This may be enough to launch the Dragon capsule, depending on the mas of the Launch Abort System (LAS). Bob Clark Experimental Private Rocket Makes Highest Test Hop Yet. by Miriam Kramer, SPACE.com Staff WriterDate: 26 December 2012 Time: 11:04 AM ET "In the latest test at SpaceX's proving grounds in MacGregor, Texas, the Grasshopper rocket flew for 29 seconds and reached a height of more than 130 feet (40 meters). A video of the Grasshopper test flight shows the rocket soaring up into the Texas sky, then smoothly descending to land on four spindly legs." http://www.space.com/19039-spacex-priva ... -test.html With reduced weight of the Merlin 1D engine while at increased efficiency, the Falcon 9 v1.1 first stage will have SSTO capability. Then ironically Elon is emulating the original purpose of the DC-X program in testing the Grasshopper VTVL stage, without realizing it. Bob Clark _________________ Single-stage-to-orbit was already shown possible 50 years ago with the Titan II first stage. Contrary to popular belief, SSTO's in fact are actually easy. Just use the most efficient engines and stages at the same time, and the result will automatically be SSTO. Blog: http://exoscientist.blogspot.com
Back to top

JamesG Space Station Commander Joined: Mon Dec 18, 2006 11:15 pm Posts: 974 Location: Columbus, GA USA	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Sun Dec 30, 2012 4:40 am But will it still have the ability to lift a second stage high/fast enough to put a Dragon with a useful cargo in orbit and do the land on it's tail trick? With existing technology and conventional configuration, it would appear that you can get SSTO or a powered landing ("Grasshopper"), but not both.
Back to top

Lourens Space Station Commander Joined: Thu Oct 27, 2005 7:44 am Posts: 707 Location: Haarlem, The Netherlands	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Sun Dec 30, 2012 9:13 am And the current SpaceX architecture doesn't have to deal with hydrogen, and the first stage won't need as much heat shielding as it's not coming back from orbital speeds. Staging is always a risk of course, but the hydraulics they're using are reusable and so far reliable. Overall it is a bit more complex than an SSTO in terms of handling, since you have two stages and Dragon to worry about, but if all of those can land autonomously on your doorstep...if it allows you to use "cheap & boring" technology I can't fault the argument. _________________ Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhere What is this spell we’re under, do you care? The might to rise above it is now within your sphere Machinae Supremacy – Sid Icarus
Back to top

Psiberzerker Space Walker Joined: Wed Jan 11, 2012 10:19 pm Posts: 189 Location: Outside Wonko the Sane's house.	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Wed Jan 02, 2013 7:29 pm The current SpaceX archetecture doesn't include an SSO. There isn't a single one anywhere that's even close to accheiving that goal. I'm not honestly convinced it's possible with current technology, but that's no reason to stop trying to figure it out. _________________ "You can't have everything, where would you put it?" -Steven Wright.
Back to top

Sigma Space Station Member Joined: Mon Dec 12, 2011 6:40 am Posts: 437 Location: California and Michigan	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Wed Jan 02, 2013 8:05 pm Get rid of two stages, shoot it from a maglev track Single stage rocket, with a single stage earth..... _________________ Let not the bindings of society hold you back from improving it.... the masses follow where the bold explore.
Back to top

Psiberzerker Space Walker Joined: Wed Jan 11, 2012 10:19 pm Posts: 189 Location: Outside Wonko the Sane's house.	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Wed Jan 02, 2013 8:22 pm That's 2 stages, and we already talked about the problems of booster cannon used in atmospheres... _________________ "You can't have everything, where would you put it?" -Steven Wright.
Back to top

Sigma Space Station Member Joined: Mon Dec 12, 2011 6:40 am Posts: 437 Location: California and Michigan	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Wed Jan 02, 2013 8:29 pm not insane speeds, just enough to add up to the lower stage, then accel using ssto engine _________________ Let not the bindings of society hold you back from improving it.... the masses follow where the bold explore.
Back to top

RGClark Space Walker Joined: Sat Jul 01, 2006 12:18 am Posts: 213	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Thu Oct 10, 2013 6:23 pm DARPA wants a reusable first stage booster: US Military Wants New Experimental Space Plane. By Leonard David, SPACE.com's Space Insider Columnist \| September 17, 2013 05:25pm ET http://www.space.com/22836-military-exp ... darpa.html The X-33 could perform this role even if you replace the composite tanks with metallic ones: Saturday, October 5, 2013 DARPA’s Spaceplane: an X-33 version. http://exoscientist.blogspot.com/2013/1 ... rsion.html This can reduce the cost to space to the $2,000 per kilo, or $1,000 per pound range, a major cut in launch costs. If it had been understood that the X-33 could be used in that role, then instead of it just being a demonstration vehicle, we could have a cut in launch costs to that range a decade ago. In an upcoming blog post I’ll show the same would have been true for the planned DC-X suborbital follow-on, the DC-X2. Then we could have had a cut in launch costs to that range two decades ago. Bob Clark _________________ Single-stage-to-orbit was already shown possible 50 years ago with the Titan II first stage. Contrary to popular belief, SSTO's in fact are actually easy. Just use the most efficient engines and stages at the same time, and the result will automatically be SSTO. Blog: http://exoscientist.blogspot.com
Back to top

JamesG Space Station Commander Joined: Mon Dec 18, 2006 11:15 pm Posts: 974 Location: Columbus, GA USA	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Thu Oct 10, 2013 7:31 pm I get a distinct deja vu feeling when reading that. A practical, more realistic (not to mention cheaper) solution would be to stick it atop a reusable F9 launcher.
Back to top

RGClark Space Walker Joined: Sat Jul 01, 2006 12:18 am Posts: 213	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Fri Oct 11, 2013 7:45 am Yes, a reusable F9 v1.1 could also cut launch costs to the $2,000 per kilo range or less. Whether though it could be done at the $5 million per launch cost DARPA wants would be dependent on how often it was reusable. Bob Clark _________________ Single-stage-to-orbit was already shown possible 50 years ago with the Titan II first stage. Contrary to popular belief, SSTO's in fact are actually easy. Just use the most efficient engines and stages at the same time, and the result will automatically be SSTO. Blog: http://exoscientist.blogspot.com
Back to top

koxinga Space Walker Joined: Sat Jun 26, 2004 2:00 pm Posts: 213	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Sun Oct 13, 2013 5:39 am 744 meters. We are getting there. Last flight of v1.0. Next up GH v1.1. http://www.youtube.com/watch?feature=pl ... ZDkItO-0a4
Back to top

Lourens Space Station Commander Joined: Thu Oct 27, 2005 7:44 am Posts: 707 Location: Haarlem, The Netherlands	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Sun Oct 13, 2013 7:16 pm RGClark wrote: Yes, a reusable F9 v1.1 could also cut launch costs to the $2,000 per kilo range or less. Whether though it could be done at the $5 million per launch cost DARPA wants would be dependent on how often it was reusable. And on how much work is required for the turnaround. Ideally, you'd land it on the landing pad, pick it up using the launcher/erector, drive it over to the (nearby) launch pad, refuel it, and launch again. In practice there would have to be some amount of inspection, even airliners have that. How much inspection depends on how many on-board sensors you can squeeze into the mass budget, the more you can measure automatically (and during the flight as well), the less you have to do manually in between, but your stage also gets more expensive. Interesting trade-offs there. _________________ Say, can you feel the thunder in the air? Just like the moment ’fore it hits – then it’s everywhere What is this spell we’re under, do you care? The might to rise above it is now within your sphere Machinae Supremacy – Sid Icarus
Back to top

JamesG Space Station Commander Joined: Mon Dec 18, 2006 11:15 pm Posts: 974 Location: Columbus, GA USA	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Sun Oct 13, 2013 8:09 pm It's a step in that direction. Just being able to refurbish the motors would make it worth while, even if you had to completely tear them down and rebuild (a la SSMEs). You pay for the hardware cost once, and then from then on you are just paying more or less the same labor you would for each flight, new or reused. SpaceX isn't pursuing it just to be cute and different.
Back to top

Sigma Space Station Member Joined: Mon Dec 12, 2011 6:40 am Posts: 437 Location: California and Michigan	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Mon Oct 14, 2013 5:40 am a maglev launching tunnel that is also a giant X-ray machine? Collect landed craft, Scan with X ray Refuel Place on track Accelerate inside closed tube with a plasma window at end and a vacuum in it, Turn plasma window into a supercavity using "Z-snap" and magnetic field on ship Accelerate plasma envelope backward greater then input friction loss RIDE THE LIGHTNING! _________________ Let not the bindings of society hold you back from improving it.... the masses follow where the bold explore.
Back to top

Psiberzerker Space Walker Joined: Wed Jan 11, 2012 10:19 pm Posts: 189 Location: Outside Wonko the Sane's house.	Re: An SSTO as "God and Robert Heinlein intended". Posted on: Mon Dec 09, 2013 6:37 pm If it has a launcher cannon, it's not a single stage. That booster is the first stage. _________________ "You can't have everything, where would you put it?" -Steven Wright.
Back to top
Display posts from previous: Sort by