Comments on: Skribit Housecleaning: Virtual SSTO w/ Drop Tanks, Biamese Vehicles, and Sea Dragon

By: Jonathan Goff

Jonathan Goff — Wed, 24 Feb 2010 06:06:18 +0000

Nels,
Good point. If they’re actual drop tanks, you have to react the whole inertial load of the propellants in those tanks through some sort of structure on the vehicle, which is going to cut even further into the benefit.

~Jon

By: Nels Anderson

Nels Anderson — Wed, 24 Feb 2010 06:03:32 +0000

If anybody’s still reading this thread, I’m wondering about the weight impact of drop tanks from a structural point of view. One of the points that John Whitehead made in his 1996 SSTO paper at the Joint Propulsion Conference was that it’s important to minimize the amount of structure that does not benefit from pressure support. In other words, things like interstages and, when you don’t have commonn bulkheads, inter-tank sections can be quite heavy.

Let’s say I build a nice, clean single-stage vehicle with a structure consisting mostly of tankage which weighs 1% of its volume in water (Whitehead’s assumption). Then I decide to strap two drop tanks onto the side. Say each has half the capacity of the original tankage. Now I’ve got those two big loads hanging off the side, and the loads on the core vehicle are no longer cylindrically symmetric. About how much weight am I going to have add to the core vehicle to support the drop tanks?

By: Brad

Brad — Thu, 24 Dec 2009 22:59:16 +0000

Regarding Sea Dragon

1,000,000 lbs payload to orbit is no doubt excessive. But a Sea Dragon technique for Saturn V class HLV payloads seems very promising to me, and a cheaper way for a nation to achieve that level of performance. When the development paths of the Saturn V, N-1 and (shudder) Ares V are considered, it seems to me the more sea based a large vehicle is the more successful it is.

By: Martijn Meijering

Martijn Meijering — Thu, 17 Dec 2009 11:21:53 +0000

On the moon that makes sense, but on Earth using a fuel in gel form would be more useful since it would give you better performance. It wouldn’t melt either.

By: A_M_Swallow

A_M_Swallow — Thu, 17 Dec 2009 04:50:58 +0000

Ice was used rather than liquid water because metals separates out and falls to the bottom of the tank. The school was doing a pretend lunar launch using a mono-propellant and they had heard that there was ice on the Moon.

On the Moon an alternative to ice is solid or slurry oxygen.

By: Martijn Meijering

Martijn Meijering — Thu, 17 Dec 2009 01:23:55 +0000

I don’t see why you would want to use ice for an Earth launch vehicle, but there may be a place for metal or carbon loaded gels.

By: Roderick Reilly

Roderick Reilly — Mon, 07 Dec 2009 16:34:59 +0000

This thread may be played out now, but I wanted to ask what you guys think of this ‘ALICE’ (nanoaluminum powder and water ice) propellant concept?

http://www.nasa.gov/home/hqnews/2009/aug/HQ_09-194_ALICE.html

There are several variants, including a gel/slurry liquid propellant concept. Supposedly, in theory, the concept could be pushed up to a high performance thrust and ISP rating.

By: Roderick Reilly

Roderick Reilly — Mon, 07 Dec 2009 16:31:23 +0000

#29. Kelly Starks:

“”"”" Eh, X-33 was never supposed to go to orbit. “”"”"

I stand corrected again. I was confusing X-33 with the intended follow-on: Venturestar, which was intended to be SSTO, as I recall.

By: Kelly Starks

Kelly Starks — Sun, 06 Dec 2009 19:37:58 +0000

>Martijn Meijering
>
>> Can’t really test a ramjet bolted to a concrete block on the ground.
>
> Couldn’t you use a compressor + diffuser/nozzle upstream of
> your ramjet inlet for ground testing? That might not be cheap
> either of course.

Testing at higher altitudes adn high speeds could be complicated — or you could borrow a wind tunnel.

This could really make building a SSTO a snap though.

By: Kelly Starks

Kelly Starks — Sun, 06 Dec 2009 19:33:14 +0000

> Roderick Reilly

>> Thats not actually true. Bioth the DC-X and X-33 had fall
>> back designs. If they ran a little heavy for pure SSTO, they
>> could add in small solid boosters to give them a little boost
>> off the pad. McDonnel Douglas all so had evaluated it for
>> occasional super heavy loads. “””””
>
> Thank you, I stand corrected. And I was on the admin staff for DC-X!

really? Smal world. A friend of mine from JSC (Rick Jurmain) was on DC-X for a while – I wound up on Spacestation and later Office of space access durring the X-33 mess.

> That is essentially a variant of what I was talking about.

Yup – though carrying drop tanks is probably better cheaper safer, then strap on solids.

> There is one thing, though: part of the “political” reason for the
> demise of X-33 is because it required additional modification to
> achieve orbit.

Eh, X-33 was never supposed to go to orbit. NASA paid a extra Billion to stop L/M from trying a orbital version. Mainly they got to into games. X-33 was loaded with cool new tech a SSTO wouldn’t really need – and L/M lost interest when they realized their was no possibility of a sale. So when L/M took a cheap route to make the composite tanks (that were heavier then the Aluminum/Lithium alternate tanks), it failed, and was the final excuse to kill the program.

Really – X-33 is a great case study of why NASA should bein charge of developing space ships or X-craft.