Space Shuttle External Tank Launchers

I could've sworn I saw Henry Spencer state recently (or I stumbled
over it in a newsgroup search recently) that the Space Shuttle's
external tank by itself had the mass fractions to be an SSTO if you
bolted 6 SSMEs onto its rear. Naturally, I can't find that statement
now that I'm looking for it.

Whether or not Mr. Spencer even said that, the idea is interesting to
me, and generated a couple of questions:

1) Could the ET be converted to an (expendable) SSTO, or be used as
the basis for an SSTO in such a fashion?
2) What would be the ballpark payload to LEO?

Mike Miller, Materials Engineer

(Mike Miller) writes:

I could've sworn I saw Henry Spencer state recently (or I stumbled
over it in a newsgroup search recently) that the Space Shuttle's
external tank by itself had the mass fractions to be an SSTO if you
bolted 6 SSMEs onto its rear. Naturally, I can't find that statement
now that I'm looking for it.

Google newgroup search on "ssto shuttle external tank spencer" yields:
http://groups.google.com/groups?selm=Bxvrv3.3tp%40zoo.toronto.edu&output=gp lain


Whether or not Mr. Spencer even said that, the idea is interesting to
me, and generated a couple of questions:

1) Could the ET be converted to an (expendable) SSTO, or be used as
the basis for an SSTO in such a fashion?
2) What would be the ballpark payload to LEO?

See:
http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml,
http://yarchive.net/space/shuttle/shuttle-c.html.

The question is not whether it is _POSSIBLE_ using "shuttle derived"
components, but whether it is possible to do it _ECONOMICALLY_ ---
and whether it would be able to carry a resonable amount of cargo.
The answer to these latter two questions appears to be "no."


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

I hear rumors that out at Thiokol (or whatever it is they call it now, think
they changed their name) they're working on a new design for the SRBs that
will enable 'em to push out 20% more thrust (yikes!). There's a test
coming up later this October I think. Gonna see if I can go to it.

If it works it could mean that the shuttle could dump the ET and get rid of
its main engine, as the two SRBs alone could launch the shuttle (and a
heavier payload) into orbit...

.... well, if the shuttle flies again.

~ Joshua

Mike Miller wrote:

I could've sworn I saw Henry Spencer state recently (or I stumbled
over it in a newsgroup search recently) that the Space Shuttle's
external tank by itself had the mass fractions to be an SSTO if you
bolted 6 SSMEs onto its rear. Naturally, I can't find that statement
now that I'm looking for it.

Whether or not Mr. Spencer even said that, the idea is interesting to
me, and generated a couple of questions:

1) Could the ET be converted to an (expendable) SSTO, or be used as
the basis for an SSTO in such a fashion?
2) What would be the ballpark payload to LEO?

Mike Miller, Materials Engineer

--
"You can't have bread and loaf."
Do you, um... Gentoo? http://www.gentoo.org
Remove DIESPAMMERS from e-mail to contact me

In article ,
Mike Miller wrote:
1) Could the ET be converted to an (expendable) SSTO, or be used as
the basis for an SSTO in such a fashion?

There's no real doubt that it is feasible, given funding and NASA's
cooperation. (Nor is this a big trick -- several past rocket stages have
had near-SSTO performance numbers, and one or two could probably have done
an SSTO demonstration flight with minimal payload if anyone had wanted it
badly enough.)

Even if you assume a generous addition of mass for structure, and no
reduction of existing structural mass -- heavier than needed in several
areas -- the ET is light enough that with six SSMEs, it could do the job
with a substantial payload. Some proposals have added one more SSME to
increase margins further.

2) What would be the ballpark payload to LEO?

50-60klb ought to be feasible; perhaps more with some effort.

Mind you, throwing away 6-7 SSMEs with each launch would make it fairly
expensive.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

"Mike Miller" wrote in message
om...
2) What would be the ballpark payload to LEO?

I got the following from a google search:

external tank empty : 30 tonnes
external tank full : 752.5 tonnes
1 SSME engine : 3.4 tonnes
(Isp for SSME = 453s = 4444 m/s)

thus:

tank + 6 SSME empty : 50.4 tonnes
tank + 6 SSME full : 773 tonnes

if payload is X, and assuming a delta-v of 9 km/sec to LEO
(to allow for gravity losses and sea-level Isp) the free-space
rocket equation gives:

exp(9000/4444) = (773 + X)/(50.4 + X)

ie X = 59.4 tonnes

The 59.4 tonnes would have to include structure to mount
the 6 SSME and the payload fairing - I dont know how much
that would be - maybe the *final* payload would be 40 tonnes?

(BIG caveat - I'm not an expert - If I've made major bloopers
please let me know - If so I promise not to drink from the
Pierian spring again!)

(Gordon D. Pusch) wrote in message ...
(Mike Miller) writes:

I could've sworn I saw Henry Spencer state recently (or I stumbled
over it in a newsgroup search recently) that the Space Shuttle's
external tank by itself had the mass fractions to be an SSTO if you
bolted 6 SSMEs onto its rear. Naturally, I can't find that statement
now that I'm looking for it.

Google newgroup search on "ssto shuttle external tank spencer" yields:
http://groups.google.com/groups?selm=Bxvrv3.3tp%40zoo.toronto.edu&output=gp lain


Whether or not Mr. Spencer even said that, the idea is interesting to
me, and generated a couple of questions:

1) Could the ET be converted to an (expendable) SSTO, or be used as
the basis for an SSTO in such a fashion?
2) What would be the ballpark payload to LEO?

See:
http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml,
http://yarchive.net/space/shuttle/shuttle-c.html.

The question is not whether it is _POSSIBLE_ using "shuttle derived"
components, but whether it is possible to do it _ECONOMICALLY_ ---
and whether it would be able to carry a resonable amount of cargo.
The answer to these latter two questions appears to be "no."


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Gordon:

Your second reference seemed to indicate it is feasible ( I couldnt
get the first to load).

(Parallax) writes:

(Gordon D. Pusch) wrote in message ...
(Mike Miller) writes:

I could've sworn I saw Henry Spencer state recently (or I stumbled
over it in a newsgroup search recently) that the Space Shuttle's
external tank by itself had the mass fractions to be an SSTO if you
bolted 6 SSMEs onto its rear. Naturally, I can't find that statement
now that I'm looking for it.

Google newgroup search on "ssto shuttle external tank spencer" yields:
http://groups.google.com/groups?selm=Bxvrv3.3tp%40zoo.toronto.edu&output=gp lain

Whether or not Mr. Spencer even said that, the idea is interesting to
me, and generated a couple of questions:

1) Could the ET be converted to an (expendable) SSTO, or be used as
the basis for an SSTO in such a fashion?
2) What would be the ballpark payload to LEO?

See:
http://www.spacefuture.com/archive/a_single_stage_to_orbit_thought_experiment.shtml,
http://yarchive.net/space/shuttle/shuttle-c.html.

The question is not whether it is _POSSIBLE_ using "shuttle derived"
components, but whether it is possible to do it _ECONOMICALLY_ ---
and whether it would be able to carry a resonable amount of cargo.
The answer to these latter two questions appears to be "no."

Gordon:

Your second reference seemed to indicate it is feasible

"Feasible," yes. However, there is a difference between "technically feasible"
and "economically viable." Shuttle components are too expensive to be expended
as one-shot SSTOs.


(I couldnt get the first to load).

[NOTE: The "first one" is the Appendix to a paper by Gary Hudson that Henry alluded to.]

Suggest you try it again. It loaded quite slowly the night I posted my reply,
but I just tried it again using several browsers, and it loaded fine under each ---
even under a =VERY= old version of Nyetscrape that chokes on a lot of websites
that are trying to comply with the new federal "accessibility regulations"...


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

"Feasible," yes. However, there is a difference between "technically
feasible"
and "economically viable." Shuttle components are too expensive to be
expended
as one-shot SSTOs.

They are even more expensive when re-used!

"Roger Stokes" wrote in message ...
"Mike Miller" wrote in message
om...
2) What would be the ballpark payload to LEO?

I got the following from a google search:

external tank empty : 30 tonnes
external tank full : 752.5 tonnes
1 SSME engine : 3.4 tonnes
(Isp for SSME = 453s = 4444 m/s)

thus:

tank + 6 SSME empty : 50.4 tonnes
tank + 6 SSME full : 773 tonnes

if payload is X, and assuming a delta-v of 9 km/sec to LEO
(to allow for gravity losses and sea-level Isp) the free-space
rocket equation gives:

exp(9000/4444) = (773 + X)/(50.4 + X)

ie X = 59.4 tonnes

The 59.4 tonnes would have to include structure to mount
the 6 SSME and the payload fairing - I dont know how much
that would be - maybe the *final* payload would be 40 tonnes?

(BIG caveat - I'm not an expert - If I've made major bloopers
please let me know - If so I promise not to drink from the
Pierian spring again!)

Made another one ... SSME ISP is 453 in vacuum. It is much lower that
that at ground level ( cant remember but around the mid 300's ). Also
the thrust is quite low so it takes it a while to get to less dense
air . The SRB's have heaps of thrust so while less efficient they do
quickly get to less dense air and a more optimal ISP.

Ben

(Gordon D. Pusch) wrote in message ...

"Feasible," yes. However, there is a difference between "technically feasible"
and "economically viable." Shuttle components are too expensive to be expended
as one-shot SSTOs.

I might already have a reply posted, or working its way through
moderation, but if I do, I don't recall what I said. So, two questions
fresh on my mind:

1) Would engine recovery in the form of a drop-off engine pod make the
ET/SSME-derived SSTO more economical?

2) Would there be much difference in R&D cost between an ET/SSME SSTO
with recoverable engine pod and a new, completely reusable SSTO with
6-7 SSMEs?

Mike Miller, Materials Engineer