Heya!
Okay I just want to ninja-add my two cents here!
I THINK that during launch the following problems occur with a winged vehicle:
Wings produce lift, and thus drag. You don't want drag, so you HAVE to reduce or avoid lift at all. Avoiding lift would be the best option, but it can't be done.. however you can put the vehicle at the side of the stack and roll / pitch accordingly, minimizing drag and optimizing your lift / drag // ascent profile.
The problem with this is, if you think about it, that the lift of the wings in a side-mount stack points 90 degrees normal to the velocity vector. This screws up your ascent profile, or am I wrong? So.. you'd have to compensate for all of this by gimbaling and so on. and if you do, you'd try to do so in the most efficient way as the STS engineers did (and get the best benefit from your weakness-compensating-measures).
If you put that vehicle on top of your stack, you get an awful lot of new problems. The wings still generate lift normal to the vel. vect., I wouldn't even compare them to canards because canards do not have an airfoil that generates lift (they have a neutral airfoil), but our vehicle's wings don't have a neutral airfoil.. and that is even worse... you still have to compensate for that by engine gimbal and elevon deflection. And the slightest deviation from your calculated course would cause MASSIVE stress on the orbiter / stack link segment, and I think at MaxQ such a deviation would rip your vehicle apart like confetti (a gust of wind, for example).
Back so the STS:
In fact what they did is a rock solid approach to "solve" the basic problems with a winged, reusable vehicle. It's called faulty design. Whatever you do to correct your design, it's still faulty and all that TPStile-checking-in-orbit and safety measures / upgrades and whatnot did not change that fact - still faulty design. In the end, the STS engineers had to live with what they got, and they did pretty well, but you better not look at the cost per flight.. it was the most expensive space vehicle ever.
I think the main problem is trying to have both: a crew transportation system AND "reasonable" payload capacity. After all that concept was the main problem of the STS. Okay, building the ISS was quite some work and the shuttle provided a means of getting things up there, but the main problem was that the shuttle was too complicated, still experimental, a compromise of contradicting design requirements and mission profiles.
Okay I'm losing the thread here..
I think Eridanus will be VERY COOL, and I think a side mount concept is a good approach.
But multistage?
Does that mean I won't be able to use Eridanus with the D3D9 client?
