After ARCA’s launch attempt of Helen rocket, we received several
questions. We listed a short FAQ and their answers:

1.Why is ARCA launching from the sea?

There are three main reasons:

1. Romania is a medium-sized European country there isn’t enough
space to safely launch a suborbital rocket. There are some launch
capabilities in the Northern Europe, like in Sweden or Norway, but
these locations are not suitable for our needs. Therefore, ARCA is
launching from the sea, not from the land, in order to avoid the populated
areas.

2: The rocket can be placed on the sea and after the balloon lift-off;
the rocket is smoothly traveling on the water surface until it will
hang beneath the balloon. On the land the rocket would need a special
device to run on the land and match the correct position with the
balloon.

3: On the sea it is possible to inflate a balloon at higher wind speeds
because the balloon can be left free to travel with the wind during
the inflation process. For instance, during Mission3 launch attempt,
the balloon traveled with the wind, on the sea surface, for almost
5 km.

2.Why ARCA prefers air launches instead of ground launches?

There are again, three main reasons:

1: The Helen and Stabilo rockets are using the hydrogen peroxide as
a monopropellant. This does not offer high performance. By launching
from a higher altitude, the engine’s specific impulse will increase.
In the case of Haas rocket it is the same situation.

2: The balloon is lifting the rocket above the Earth’s dense
atmosphere and there is no significant drag on the rocket.

3: A launch pad is not needed anymore.

3.The Helen rocket stages float on the sea. Why did they not sink?

Helen is using a pressure fed system, so the fuel tanks were fueled
with only half of the total capacity. The rest of the tanks were left
empty. The fuel was transferred from the Venus ship, from the blue
spherical tanks to the rocket stages.

4.Was there sufficient force on the balloon able to lift the rocket
stages and the payload?

No, the balloon was inflated only 20% of the planned volume since
the inflation arms twisted around the balloon. Despite of the team’s
efforts to untwist the balloon, when the balloon was finally released
from the arms, it was too late. We were close to the sunset and the
Sun could not warm the air inside the balloon as it should.

5.When is such a balloon ready for launch?

On the pictures you can see a large orange sphere that is barely floating
on the sea. It was loaded with water and attached to the balloon.
When the balloon is ready for launch, the sphere will be almost pulled
out from the water. Then the sphere is detached from the balloon and
the balloon is free to fly.

6.The Helen rocket system will be used for a new launch attempt?

Yes. The team and the Helen rocket will return to the launch site
in the spring of 2010. ARCA will improve the balloon and the system
itself.

7.Why is ARCA using the “Popescu-Diaconu” method on the
Helen system?

This method will be used also for a part of the Google Lunar X Prize,
Moon flight. We want to test it on a suborbital flight and if successful
to use it on some part of the Moon flight.

8.
Is the Helen system too dependent on the weather conditions?

Yes, it is very dependent of weather conditions, more than a ground
launched system. After numerous analyses, we concluded that it is
a suitable system, from financial, logistical, time-effectiveness
and technical point of view. Of course, it is not appropriate to launch
satellites on a regular basis, but we have in mind only one objective:
to win the Google Lunar X Prize, and in a competition, the most suitable
system is not always the most efficient.

9.Won’t the cables burn?

No, the temperature of the exhaust is not as high as for other propulsion
solutions. The engine itself is made out of composite materials and
the temperature has never a problem.

10.The stages are following the same trajectory. Won’t the stages
collide after separation?

No. There is an interval of 3…5 seconds after separation when
the stages are running simultaneously. Since there is almost no mass
to stabilize the upper stage, this stage will change the trajectory
enough to avoid a collision.